Previous studies showed that low dose radiation (LDR) could stimulate the immune system in both animal and human populations. This paper reviews the present status of relevant research as support to the use of LDR in clinical practice for cancer prevention and treatment. It has been demonstrated that radiation-induced changes in immune activity follows an inverse J-shaped curve, i.e., low dose stimulation and high dose suppression. The stimulation of immunity by LDR concerns most anticancer parameters, including antibody formation, natural killer activity, secretion of interferon and other cytokines as well as other cellular changes. Animal studies have revealed that LDR retards tumor growth, decreases cancer metastasis, and inhibits carcinogenesis induced by high dose radiation. These effects of LDR on cancer control were found to be related to its stimulation on immunity. The experimental data may well explain the efficacy of the clinical trial of LDR in the treatment of cancer.
Repetitive exposure of diabetic mice to low-dose radiation (LDR) at 25 mGy could significantly attenuate diabetes-induced renal inflammation, oxidative damage, remodeling, and dysfunction, for which, however, the underlying mechanism remained unknown. The present study explored the effects of LDR on the expression and function of Akt and Nrf2 in the kidney of diabetic mice. C57BL/6J mice were used to induce type 1 diabetes with multiple low-dose streptozotocin. Diabetic and age-matched control mice were irradiated with whole body X-rays at either single 25 mGy and 75 mGy or accumulated 75 mGy (25 mGy daily for 3 days) and then sacrificed at 1–12 h for examining renal Akt phosphorylation and Nrf2 expression and function. We found that 75 mGy of X-rays can stimulate Akt signaling pathway and upregulate Nrf2 expression and function in diabetic kidneys; single exposure of 25 mGy did not, but three exposures to 25 mGy of X-rays could offer a similar effect as single exposure to 75 mGy on the stimulation of Akt phosphorylation and the upregulation of Nrf2 expression and transcription function. These results suggest that single 75 mGy or multiple 25 mGy of X-rays can stimulate Akt phosphorylation and upregulate Nrf2 expression and function, which may explain the prevention of LDR against the diabetic nephropathy mentioned above.
The present paper aims at studying the role of B7/CD28 interaction and related cytokine production in the immunological changes after exposure to different doses of ionizing radiation.
The stimulatory effect of low dose radiation (LDR) on the proliferative response of lymphocytes to Con A was found to require the presence of APCs. The addition of APCs obtained from both low- and high-dose-irradiated mice to splenic lymphocytes separated from low-dose-irradiated mice caused stimulation of lymphocyte proliferation. B7-1/2 expression on APCs was up-regulated after both low and high doses of radiation. There was up-regulation of CD28 expression on splenic and thymic lymphocytes after LDR and its suppression after high dose radiation (HDR), and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) expression showed changes in the opposite direction. IL-12 secretion by macrophages was stimulated after both low and high doses of radiation, but IL-10 synthesis by splenocytes was suppressed by low dose radiation and up-regulated by high dose radiation.
The status of CD28/CTLA-4 expression on T lymphocytes in the presence of up-regulated B7 expression on APCs determined the outcome of the immune changes in response to radiation, i.e., up-regulation of CD28 after LDR resulted in immunoenhancement, and up-regulation of CTLA-4 associated with down-regulation of CD28 after HDR led to immunosuppression. Both low and high doses of radiation up-regulated B7-1/2 expression on APCs. After LDR, the stimulated proliferative effect of increased IL-12 secretion by APCs, reinforced by the suppressed secretion of IL-10, further strengthened the intracellular signaling induced by B7-CD28 interaction.
Despite the fact that high doses of radiation are detrimental, low dose radiation (LDR) often protects the organism against a subsequent exposure of lethal doses of radiation. Present study was undertaken to understand the role of Mre11, Rad50 and Nbs1 genes in the low dose radio-adapted human peripheral blood mononuclear cells (PBMCs). Optimum time interval between low dose (0.07 Gy) and high dose (5.0 Gy) of 60Co-γ-radiation was observed to be 5.0 hours, at which PBMCs showed maximum LDR induced resistance (RIR). At cytogenetic level, micronuclei frequency was found to be reduced in LDR pre-irradiated PBMCs subsequently exposed to high dose radiation (HDR) as compared to controls. At transcriptional level, with reference to sham-irradiated cells significantly (p≤0.05) altered expression of Mre11, Rad50 and Nbs1 genes was observed in low dose irradiated cells. At protein level, Mre11, Rad50 and Nbs1 were enhanced significantly (p≤0.05) in low dose pre-irradiated cells subsequently exposed to high dose of radiation as compared to only high dose irradiated cells. Transcriptional as well as translational modulation in the expression of MRN complex components upon low dose irradiation may confer its participation in repair pathways, resulting in induced resistance.
ionizing radiation; radioadaptive response; micronuclei; MRN complex; gene expression; immuno-blotting
We previously determined that AKR/J mice housed in a low-dose-rate (LDR) (137Cs, 0.7 mGy/h, 2.1 Gy) γ-irradiation facility developed less spontaneous thymic lymphoma and survived longer than those receiving sham or high-dose-rate (HDR) (137Cs, 0.8 Gy/min, 4.5 Gy) radiation. Interestingly, histopathological analysis showed a mild lymphomagenesis in the thymus of LDR-irradiated mice. Therefore, in this study, we investigated whether LDR irradiation could trigger the expression of thymic genes involved in the DNA repair process of AKR/J mice. The enrichment analysis of Gene Ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways showed immune response, nucleosome organization, and the peroxisome proliferator-activated receptors signaling pathway in LDR-irradiated mice. Our microarray analysis and quantitative polymerase chain reaction data demonstrated that mRNA levels of Lig4 and RRM2 were specifically elevated in AKR/J mice at 130 days after the start of LDR irradiation. Furthermore, transcriptional levels of H2AX and ATM, proteins known to recruit DNA repair factors, were also shown to be upregulated. These data suggest that LDR irradiation could trigger specific induction of DNA repair-associated genes in an attempt to repair damaged DNA during tumor progression, which in turn contributed to the decreased incidence of lymphoma and increased survival. Overall, we identified specific DNA repair genes in LDR-irradiated AKR/J mice.
AKR/J mice; DNA repair genes; low-dose-rate radiation; thymic lymphoma
MLH1 is a key DNA mismatch repair (MMR) protein involved in maintaining genomic stability by participating in the repair of endogenous and exogenous mispairs in the daughter strands during S-phase. Exogenous mispairs can result following treatment with several classes of chemotherapeutic drugs as well as with ionizing radiation (IR). In this study, we investigated the role of the MLH1 protein in determining the cellular and molecular responses to prolonged low dose rate (LDR) IR, which is similar to the clinical use of cancer brachytherapy.
An isogenic pair of MMR+ (MLH1+) and MMR− (MLH1−) human colorectal cancer HCT116 cells were exposed to prolonged LDR-IR (1.3–17cGy/h × 24–96 h). The clonogenic survival and gene mutation rates were examined. Cell cycle distribution was analyzed with flow cytometry. Changes in selected DNA damage repair proteins, DNA damage response proteins and cell death marker proteins were examined with Western blotting.
MLH1+ HCT116 cells showed greater radiosensitivity with enhanced expression of apoptotic and autophagic markers; a reduced HPRT gene mutation rate; and more pronounced cell cycle alterations (increased late S population and a G2/M arrest) following LDR-IR compared to MLH1− HCT116 cells. Importantly, a progressive increase in MLH1 protein levels was found in MLH1+ cells during prolonged LDR-IR, which was temporally correlated with a progressive decrease in Rad51 protein (involved in homologous recombination, HR) levels.
MLH1 status significantly affects cellular responses to prolonged LDR-IR. MLH1 may enhance cell radiosensitivity to prolonged LDR-IR through inhibition of HR (via inhibition of Rad51).
mismatch repair; low dose rate IR; MLH1; Rad51; late S phase
Crew members on space missions inevitably are exposed to low background radiation and can receive much higher doses during solar particle events (SPE) that consist primarily of protons. Ionizing radiation could cause lung pathologies. Cell adhesion molecules (CAM) are believed to participate in fibrogenesis. Interactions between CAM and extracellular matrix (ECM) affect epithelial repair mechanisms in the lung. However, there are very limited data on biological effects of protons on normal lung tissue. Numerous reports have shown that exposure to low-dose/low-dose-rate (LDR) radiation can result in radioadaptation that renders cells more resistant to subsequent acute radiation. The goal of this study was to compare expression of genes associated with ECM and CAM, as well as critical profibrotic mediators, in mouse lungs after acute irradiation with photons and protons, and also determine whether pre-exposure to LDR γ-rays induces an adaptive effect.
Overall, a marked difference was present in the proton vs. photon groups in gene expression. When compared to 0 Gy, more genes were affected by protons than by photons at both time points (11 vs. 6 on day 21 and 14 vs. 8 on day 56), and all genes affected by protons were upregulated. Many genes were modulated by LDR γ-rays when combined with photons or protons. Col1a1, mmp14, and mmp15 were significantly upregulated by all radiation regimens on day 21. Similarly, the change in expression of profibrotic proteins was also detected after acute and combination irradiation.
These data show that marked differences were present between acutely delivered protons and photons in modulating genes, and the effect of protons was more profound than that of photons. Pre-exposure to LDR γ-rays ‘normalized’ some genes that were modified by acute irradiation.
In this study, a mechanism in which low-dose hyper-radiosensitivity (HRS) is permanently removed, induced by low-dose-rate (LDR) (0.2–0.3 Gy/h for 1 h) but not by high-dose-rate priming (0.3 Gy at 40 Gy/h) was investigated. One HRS-negative cell line (NHIK 3025) and two HRS-positive cell lines (T-47D, T98G) were used. The effects of different pretreatments on HRS were investigated using the colony assay. Cell-based ELISA was used to measure nitric oxide synthase (NOS) levels, and microarray analysis to compare gene expression in primed and unprimed cells. The data show how permanent removal of HRS, previously found to be induced by LDR priming irradiation, can also be induced by addition of nitric oxide (NO)-donor DEANO combined with either high-dose-rate priming or exposure to prolonged cycling hypoxia followed by reoxygenation, a treatment not involving radiation. The removal of HRS appears not to involve DNA damage induced during priming irradiation as it was also induced by LDR irradiation of cell-conditioned medium without cells present. The permanent removal of HRS in LDR-primed cells was reversed by treatment with inducible nitric oxide synthase (iNOS) inhibitor 1400W. Furthermore, 1400W could also induce HRS in an HRS-negative cell line. The data suggest that LDR irradiation for 1 h, but not 15 min, activates iNOS, and also that sustained iNOS activation is necessary for the permanent removal of HRS by LDR priming. The data indicate that nitric oxide production is involved in the regulatory processes determining cellular responses to low-dose-rate irradiation.
nitric oxide; inducible nitric oxide synthase; hyper-radiosensitivity; low dose-rate
The frequency of dicentrics + ring (dic/cell) and total chromosome aberrations (dicentrics, rings and excess acentrics, etc.) per cell (TAb/cell) has been studied in 50 male and female volunteers after high or low dose rate (HDR, LDR) irradiation of peripheral blood lymphocytes. The mean male aberration frequencies per cell after HDR irradiation were 0.38 dic/cell and 0.61 TAb/cell; following LDR irradiation, the mean aberration frequencies were 0.28 dic/cell and 0.45 TAb/cell. Equivalent female values after HDR irradiation were 0.42 dic/cell and 0.71 TAb/cell; after LDR irradiation, the mean aberration frequencies were 0.30 dic/cell and 0.48 TAb/cell. Analysis of variance showed that there was a highly significant difference between males and females have a greater HDR, but not LDR, irradiation It is concluded from this study that females have a greater variability in their radioresponse, and that this variability is related to progesterone, which has a profound effect upon radiosensitivity, as measured by cytogenetic end points.
We have previously shown that the anti-malarial agent chloroquine can abrogate the lethal cellular effects of low dose-rate (LDR) radiation in vitro, most likely by activating the ataxia-telangiectasia mutated (ATM) protein. Here, we demonstrate that chloroquine treatment also protects against lethal doses of LDR radiation in vivo.
Methods and Materials
C57BL/6 mice were irradiated with total of 12.8 Gy delivered at 9.4 cGy/hr. ATM null mice from the same background were used to determine the influence of ATM. Chloroquine was administered by two intraperitoneal injections of 59.4 μg per 17 g of body weight, 24 hrs and 4 hrs before irradiation. Bone marrow cells isolated from tibia, fibula and vertebral bones were transplanted into lethally irradiated CD45 congenic recipient mice by retro orbital injection. Chimerism was assessed by flow cytometry. In vitro methyl cellulose colony forming assay of whole bone marrow cells as well as FACS analysis of lineage depleted cells was used to assess the effect of chloroquine on progenitor cells.
Mice pretreated with chloroquine prior to radiation exhibited a significantly higher survival rate compared to mice treated with radiation alone (80 vs.31 percent, p=0.0026). Chloroquine administration prior to radiation did not impact the survival of ATM null mice (p=0.86). Chloroquine also had a significant effect on the early engraftment of bone marrow cells from the irradiated donor mice 6 weeks after the transplantation (4.2 percent vs. 0.4 percent, p=0.015).
Chloroquine administration prior to radiation had a significant effect on the survival of normal but not ATM null mice strongly suggesting that the in vivo effect like the in vitro effect is also ATM dependent. Chloroquine improved the early engraftment of bone marrow cells from LDR irradiated mice, presumably by protecting the progenitor cells from radiation injury. Chloroquine thus could serve as a very useful drug for protection against the harmful effects of LDR radiation.
Low dose rate radiation; Chloroquine; Hematopoietic progenitor cells; Ataxia telangiectasia mutated; ATM activation
Low-dose ionizing radiation (LDR) may lead to suppression of smoking-related lung cancer. We examined the effects of a known cigarette smoke carcinogen Benzo[a]pyrene (B[a]P) alone or in combination with fractionated low-dose gamma radiation (60 – 600 mGy total dose) on the induction of lung neoplasms in the A/J mouse. Our results show that 600 mGy of gamma radiation delivered in six biweekly fractions of 100 mGy starting 1 month after B[a]P injection significantly inhibits the development of lung adenomas per animal induced by B[a]P. Our data also indicated that the six biweekly doses suppressed the occurrence of spontaneous hyperplastic foci in the lung, although this suppression failed to reach statistical significance when analyzed as average foci per lung possibly related to the small sample sizes used for the control and test groups.
Low-dose gamma-radiation; Benzo[a]pyrene; lung cancer
To clarify the significant clinicopathological and postdosimetric parameters to predict PSA bounce in patients who underwent low-dose-rate brachytherapy (LDR-brachytherapy) for prostate cancer.
We studied 200 consecutive patients who received LDR-brachytherapy between July 2004 and November 2008. Of them, 137 patients did not receive neoadjuvant or adjuvant androgen deprivation therapy. One hundred and forty-two patients were treated with LDR-brachytherapy alone, and 58 were treated with LDR-brachytherapy in combination with external beam radiation therapy. The cut-off value of PSA bounce was 0.1 ng/mL. The incidence, time, height, and duration of PSA bounce were investigated. Clinicopathological and postdosimetric parameters were evaluated to elucidate independent factors to predict PSA bounce in hormone-naïve patients who underwent LDR-brachytherapy alone.
Fifty patients (25%) showed PSA bounce and 10 patients (5%) showed PSA failure. The median time, height, and duration of PSA bounce were 17 months, 0.29 ng/mL, and 7.0 months, respectively. In 103 hormone-naïve patients treated with LDR-brachytherapy alone, and univariate Cox proportional regression hazard model indicated that age and minimal percentage of the dose received by 30% and 90% of the urethra were independent predictors of PSA bounce. With a multivariate Cox proportional regression hazard model, minimal percentage of the dose received by 90% of the urethra was the most significant parameter of PSA bounce.
Minimal percentage of the dose received by 90% of the urethra was the most significant predictor of PSA bounce in hormone-naïve patients treated with LDR-brachytherapy alone.
Prostate cancer; Brachytherapy; PSA bounce; Post-dosimetry; UD90 (%)
The health effects of low-dose radiation (LDR) have been the concern of the academic spheres, regulatory bodies, governments, and the public. Among these effects, the most important is carcinogenesis. In view of the importance of immune surveillance in cancer control, the dose-response relationship of the changes in different cell types of the immune system after whole-body irradiation is analyzed on the basis of systemic data from the author’s laboratory in combination with recent reports in the literature. For T lymphocytes J- or inverted J-shaped curves are usually demonstrated after irradiation, while for macrophages dose-response curves of chiefly stimulation with irregular patterns are often observed. The intercellular reactions between the antigen presenting cell (APC) and T lymphocyte (TLC) in the immunologic synapse via expression of surface molecules and secretion of cytokines by the two cell types after different doses of radiation are illustrated. The different pathways of signal transduction thus facilitated in the T lymphocyte by different doses of radiation are analyzed to explain the mechanism of the phenomenon of low-dose stimulation and high-dose suppression of immunity. Experimental and clinical data are cited to show that LDR retards tumor growth, reduces metastasis, increases the efficacy of conventional radiotherapy and chemotherapy as well as alleviates the suppression of immunity due to tumor burden. The incidence of thymic lymphoma after high-dose radiation is lowered by preexposure to low-dose radiation, and its mechanism is supposed to be related to the stimulation of anticancer immunity induced by low-dose radiation. Recent reports on lowering of standardized cancer mortality rate and all cause death rate of cohorts occupationally exposed to low-dose radiation from the US, UK, and Canada are cited.
dose-response curves; immune surveillance; molecular and cellular mechanisms; cancer risk
To determine whether proton radiation affects coagulation.
Material and methods
Ferrets were exposed to solar particle event-like proton radiation at doses of 0, 25, 100, or 200 centigray (cGy), and dose rates of 50 cGy/minute (high dose rate or HDR) or 50 cGy/hour (low dose rate or LDR). Plasma was isolated from blood collected prior to radiation exposure and at 3–7 h post-radiation. Prothrombin time (PT) assays and activated partial thromboplastin time (aPTT) assays were performed as were mixing studies to determine the coagulation factors involved.
HDR and LDR exposure led to statistically significant increases in PT values. It was determined that the HDR-induced increase in PT was due to Factor VII, while Factors II, V, and VII contributed to the LDR-induced increase in PT values. Only acute LDR exposure caused an increase in aPTT values, which remained elevated for 48 h post-irradiation (which was the latest time assayed in these studies). Mixing studies revealed that Factor IX contributed to the increased aPTT values. A majority of the animals exposed at the LDR had an International Normalized Ratio approaching or surpassing 2.0.
PT/aPTT assays resulted in increased clotting times due to different coagulation factors, indicating potential radiation-induced coagulopathy.
Radiation; haematology – radiation; low dose rate
Brachytherapy results in better dose distribution compared with other treatments because of steep dose reduction in the surrounding normal tissues. Excellent local control rates and acceptable side effects have been demonstrated with brachytherapy as a sole treatment modality, a postoperative method, and a method of reirradiation. Low-dose-rate (LDR) brachytherapy has been employed worldwide for its superior outcome. With the advent of technology, high-dose-rate (HDR) brachytherapy has enabled health care providers to avoid radiation exposure. This therapy has been used for treating many types of cancer such as gynecological cancer, breast cancer, and prostate cancer. However, LDR and pulsed-dose-rate interstitial brachytherapies have been mainstays for head and neck cancer. HDR brachytherapy has not become widely used in the radiotherapy community for treating head and neck cancer because of lack of experience and biological concerns. On the other hand, because HDR brachytherapy is less time-consuming, treatment can occasionally be administered on an outpatient basis. For the convenience and safety of patients and medical staff, HDR brachytherapy should be explored. To enhance the role of this therapy in treatment of head and neck lesions, we have reviewed its outcomes with oral cancer, including Phase I/II to Phase III studies, evaluating this technique in terms of safety and efficacy. In particular, our studies have shown that superficial tumors can be treated using a non-invasive mold technique on an outpatient basis without adverse reactions. The next generation of image-guided brachytherapy using HDR has been discussed. In conclusion, although concrete evidence is yet to be produced with a sophisticated study in a reproducible manner, HDR brachytherapy remains an important option for treatment of oral cancer.
brachytherapy; oral cancer; high dose rate
The Genitourinary Cancer Disease Site Group (GU DSG) and Cancer Care Ontario’s Program in Evidence-Based Care (PEBC) in Ontario, Canada developed a guideline on low-dose rate brachytherapy (LDR-BT) in patients with early-stage low-grade prostate cancer in 2001. The current updated guideline focuses on the research questions regarding the effect of LDR-BT alone, the effect of LDR-BT with external beam radiation therapy (EBRT) and the selection of an isotope.
This guideline was developed by using the methods of the Practice Guidelines Development Cycle and the core methodology was a systematic review. MEDLINE and EMBASE (from January 1996 to October 2011), the Cochrane Library, main guideline websites, and main annual meeting abstract websites specific for genitourinary diseases were searched. Internal and external reviews of the draft guideline were conducted.
The draft guideline was developed according to a total of 10 systematic reviews and 55 full text articles that met the pre-planned study selection criteria. The quality of evidence was low to moderate. The final report reflects integration of the feedback obtained through the internal review (two oncologists and a methodologist) and external review (five target reviewers and 48 professional consultation reviewers) process, with final approval given by the GU DSG and the PEBC.
The main recommendations are: (1) For patients with newly diagnosed low-risk or intermediate-risk prostate cancer who require or choose active treatment, LDR-BT alone is a treatment option as an alternative to EBRT alone or RP alone; and (2) I-125 and Pd-103 are each reasonable isotope options.
C57Bl/6 mice develop obesity and mild hyperglycemia when fed a high-fat diet (HFD). Although diet-induced obesity (DIO) is a widely studied model of type 2 diabetes, little is known about β-cell failure in these mice.
RESEARCH DESIGN AND METHODS
DIO mice were separated in two groups according to body weight gain: low- and high-HFD responders (LDR and HDR). We examined whether mild hyperglycemia in HDR mice is due to reduced β-cell mass or function and studied islet metabolism and signaling.
HDR mice were more obese, hyperinsulinemic, insulin resistant, and hyperglycemic and showed a more altered plasma lipid profile than LDR. LDR mice largely compensated insulin resistance, whereas HDR showed perturbed glucose homeostasis. Neither LDR nor HDR mice showed reduced β-cell mass, altered islet glucose metabolism, and triglyceride deposition. Insulin secretion in response to glucose, KCl, and arginine was impaired in LDR and almost abolished in HDR islets. Palmitate partially restored glucose- and KCl-stimulated secretion. The glucose-induced rise in ATP was reduced in both DIO groups, and the glucose-induced rise in Ca2+ was reduced in HDR islets relatively to LDR. Glucose-stimulated lipolysis was decreased in LDR and HDR islets, whereas fat oxidation was increased in HDR islets only. Fatty acid esterification processes were markedly diminished, and free cholesterol accumulated in HDR islets.
β-Cell failure in HDR mice is not due to reduced β-cell mass and glucose metabolism or steatosis but to a secretory dysfunction that is possibly due to altered ATP/Ca2+ and lipid signaling, as well as free cholesterol deposition.
The purpose of this work was the biological comparison between Low Dose Rate (LDR) and Pulsed Dose Rate (PDR) in cervical cancer regarding the discontinuation of the afterloading system used for the LDR treatments at our Institution since December 2009.
Material and methods
In the first phase we studied the influence of the pulse dose and the pulse time in the biological equivalence between LDR and PDR treatments using the Linear Quadratic Model (LQM). In the second phase, the equivalent dose in 2 Gy/fraction (EQD2) for the tumor, rectum and bladder in treatments performed with both techniques was evaluated and statistically compared. All evaluated patients had stage IIB cervical cancer and were treated with External Beam Radiotherapy (EBRT) plus two Brachytherapy (BT) applications. Data were collected from 48 patients (26 patients treated with LDR and 22 patients with PDR).
In the analyses of the influence of PDR parameters in the biological equivalence between LDR and PDR treatments (Phase 1), it was calculated that if the pulse dose in PDR was kept equal to the LDR dose rate, a small the-rapeutic loss was expected. If the pulse dose was decreased, the therapeutic window became larger, but a correction in the prescribed dose was necessary. In PDR schemes with 1 hour interval between pulses, the pulse time did not influence significantly the equivalent dose. In the comparison between the groups treated with LDR and PDR (Phase 2) we concluded that they were not equivalent, because in the PDR group the total EQD2 for the tumor, rectum and bladder was smaller than in the LDR group; the LQM estimated that a correction in the prescribed dose of 6% to 10% was ne-cessary to avoid therapeutic loss.
A correction in the prescribed dose was necessary; this correction should be achieved by calculating the PDR dose equivalent to the desired LDR total dose.
brachytherapy; cervical cancer; LDR; PDR; EQD2; LQM
BACKGROUND: Corticosteroid trials are an important part of the assessment of patients with chronic airways obstruction, but false negative results will occur if the treatment is not taken. To determine compliance low dose phenobarbitone has been used as a marker. METHODS: Thirty six patients referred to a chest clinic for assessment of their airways obstruction were studied. They were instructed to take eight capsules (each containing 5 mg prednisolone and 0.5 mg phenobarbitone) per day for two weeks. The response was assessed by home peak flow monitoring and clinic spirometric tests. Plasma phenobarbitone levels were measured after the trial to enable calculation of the dose to plasma concentration ratio (level to dose ratio, LDR) and the result was compared with the reference range for fully compliant individuals. RESULTS: Five patients defaulted from follow up, 23 had LDR values within the expected range, and eight had low LDR values consistent with poor compliance. The nine patients with steroid responsive disease (> 20% improvement in peak flow or spirometric parameters) all had LDR values in the expected range. CONCLUSION: Excluding those who defaulted whose compliance must be questionable, eight (26%) patients did not fully comply with the steroid trial. Not all patients who fail to respond to a two week home steroid trial have a steroid "unresponsive" disease.
The current radiation safety paradigm using the linear no-threshold (LNT) model is based on the premise that even the smallest amount of radiation may cause mutations increasing the risk of cancer. Autopsy studies have shown that the presence of cancer cells is not a decisive factor in the occurrence of clinical cancer. On the other hand, suppression of immune system more than doubles the cancer risk in organ transplant patients, indicating its key role in keeping occult cancers in check. Low dose radiation (LDR) elevates immune response, and so it may reduce rather than increase the risk of cancer. LNT model pays exclusive attention to DNA damage, which is not a decisive factor, and completely ignores immune system response, which is an important factor, and so is not scientifically justifiable. By not recognizing the importance of the immune system in cancer, and not exploring exercise intervention, the current paradigm may have missed an opportunity to reduce cancer deaths among atomic bomb survivors. Increased antioxidants from LDR may reduce aging-related non-cancer diseases since oxidative damage is implicated in these. A paradigm shift is warranted to reduce further casualties, reduce fear of LDR, and enable investigation of potential beneficial applications of LDR.
Radiation safety; Low dose radiation; LNT model; Immune system; Antioxidant stimulation; Aging-related diseases
Accelerated tumor repopulation has significant implications in low-dose-rate (LDR) brachytherapy. Repopulation onset time remains undetermined for cervical cancer. The purpose of this study was to determine the onset time of accelerated repopulation in cervical cancer using clinical data.
Methods and Materials
The linear-quadratic (LQ) model extended for tumor repopulation was used to analyze the clinical data and MRI-based 3D tumor volumetric regression data of 80 cervical cancer patients who received external beam radiotherapy (EBRT) and low dose rate (LDR) brachytherapy. The LDR dose was converted to EBRT dose in 1.8 Gy fractions using the LQ formula, and the total dose ranged from 61.4 to 99.7 Gy. The patients were divided into 11 groups according to total dose and treatment time. The tumor control probability (TCP) was calculated for each group. The least χ2 method was used to fit the TCP data with two free parameters: onset time (Tk) of accelerated repopulation and the number of clonogens (K) while other LQ model parameters were adopted from the literature, due to the limited patient data.
Among the 11 patient groups, TCP varied from 33% to 100% as a function of radiation dose and overall treatment time. Higher dose and shorter treatment duration were associated higher TCP. Using the LQ model, the best fit was achieved with the onset time Tk=19 days, K=139, with uncertainty ranges of (11, 22) days for Tk, and (48, 1822) for K, respectively.
This is the first report of accelerated repopulation onset time in cervical cancer, derived directly from the clinical data using the LQ model. Our study verifies that accelerated repopulation does exist in cervical cancer and has a relatively short onset time. Dose escalation may be required to compensate for the effects of tumor repopulation if the radiation therapy course is protracted.
Cervical cancer; Radiation therapy; Tumor control probability; Tumor repopulation onset time; Linear-quadratic model
AIM: To compare the ligase detection reaction (LDR) and real-time PCR for detection of low abundant YMDD mutants in patients with chronic hepatitis B infection.
METHODS: Mixtures of plasmids and serum samples from 52 chronic hepatitis B patients with low abundant lamivudine-resistant mutations were tested with LDR and real-time PCR. Time required and reagent cost for both assays were evaluated.
RESULTS: Real-time PCR detected 100, 50, 10, 1 and 0.1% of YIDD plasmid, whereas LDR detected 100, 50, 10, 1, 0.1, and 0.01% of YIDD plasmid, in mixtures with YMDD plasmid of 106 copies/mL. Among the 52 clinical serum samples, completely concordant results were obtained for all samples by both assays, and 39 YIDD, 9 YVDD, and 4 YIDD/YVDD were detected. Cost and time required for LDR and real-time PCR are 60/80 CNY (8/10.7 US dollars) and 4.5/2.5 h, respectively.
CONCLUSION: LDR and real-time PCR are both sensitive and inexpensive methods for monitoring low abundant YMDD mutants during lamivudine therapy in patients with chronic hepatitis B. LDR is more sensitive and less expensive, while real-time PCR is more rapid.
YMDD mutants; Hepatitis B virus; Real-time PCR; Ligase detection reaction
To evaluate whether Point A asymmetry in low dose-rate (LDR) brachytherapy is associated with local control (LC), disease-free survival (DFS) and/or overall survival (OS).
Material and methods
A retrospective analysis of disease control and survival outcomes was conducted for patients who underwent LDR brachytherapy for advanced cervical cancer. Institutional protocol entailed concurrent chemotherapy and whole pelvis radiotherapy (WPRT) over 5 weeks, followed by placement of Fletcher-Suit tandem and colpostat applicators at weeks 6 and 8. Objective Point A doses, 80-85 Gy, were accomplished by placement of Cesium-137 (Cs-137) sources. Cox proportional hazards regression models were used to assess associations between disease control and survival endpoints with variables of interest.
The records of 50 patients with FIGO stage IB1-IVA cervical cancer undergoing LDR brachytherapy at our institution were identified. Thirty of these patients had asymmetry > 2.5%, and 11 patients had asymmetry > 5%. At a median survivor follow-up of 20.25 months, 15 patients had experienced disease failure (including 5 cervical/vaginal apex only failures and 2 failures encompassing the local site). Right/left dose asymmetry at Point A was associated with statistically significantly inferior LC (p = 0.035) and inferior DFS (p = 0.011) for patients with mean Point A dose of > 80 Gy. Insufficient evidence existed to conclude an association with OS.
LDR brachytherapy may be associated with clinically significant dose asymmetry. The present study demonstrates that patients with Point A asymmetry have a higher risk of failure for DFS and LC.
brachytherapy; cervical; point A; Fletcher-Suit system
To compare the efficacy and safety of high dose rate (HDR) and low dose rate (LDR) brachytherapy in treating early-stage oral cancer.
A systematic search of MEDLINE, EMBASE and Cochrane Library databases, restricted to English language up to June 1, 2012, was performed to identify potentially relevant studies.
Only randomized controlled trials (RCT) and controlled trials that compared HDR to LDR brachytherapy in treatment of early-stage oral cancer (stages I, II and III) were of interest.
Data Extraction and Synthesis
Two investigators independently extracted data from retrieved studies and controversies were solved by discussion. Meta-analysis was performed using RevMan 5.1. One RCT and five controlled trials (607 patients: 447 for LDR and 160 for HDR) met the inclusion criteria. The odds ratio showed no statistically significant difference between LDR group and HDR group in terms of local recurrence (OR = 1.12, CI 95% 0.62–2.01), overall mortality (OR = 1.01, CI 95% 0.61–1.66) and Grade 3/4 complications (OR = 0.86, CI 95% 0.52–1.42).
This meta-analysis indicated that HDR brachytherapy was a comparable alternative to LDR brachytherapy in treatment of oral cancer. HDR brachytherapy might become a routine choice for early-stage oral cancer in the future.
The literature supporting high-dose rate brachytherapy (HDR) in the treatment of cervical carcinoma derives primarily from retrospective series. However, controversy still persists regarding the efficacy and safety of HDR brachytherapy compared to low-dose rate (LDR) brachytherapy, in particular, due to inadequate tumor coverage for stage III patients. Whether LDR or HDR brachytherapy produces better results for these patients in terms of survival rate, local control rate and the treatment complications remain controversial.
A meta-analysis of RCT was performed comparing LDR to HDR brachytherapy for cervix cancer treated for radiotherapy alone. The MEDLINE, EMBASE, CANCERLIT and Cochrane Library databases, as well as abstracts published in the annual proceedings were systematically searched. We assessed methodological quality for each outcome by grading the quality of evidence using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology. We used "recommend" for strong recommendations, and "suggest" for weak recommendations.
Pooled results from five randomized trials (2,065 patients) of HDR brachytherapy in cervix cancer showed no significant increase of mortality (p = 0.52), local recurrence (p = 0.68), or late complications (rectal; p = 0.7, bladder; p = 0.95 or small intestine; p = 0.06) rates as compared to LDR brachytherapy. In the subgroup analysis no difference was observed for overall mortality and local recurrence in patients with clinical stages I, II and III. The quality of evidence was low for mortality and local recurrence in patients with clinical stage I, and moderate for other clinical stages.
Our meta-analysis shows that there are no differences between HDR and LDR for overall survival, local recurrence and late complications for clinical stages I, II and III. By means of the GRADE system, we recommend the use of HDR for all clinical stages of cervix cancer.