In contrast to the conventional radiotherapy/chemoradiotherapy paradigms used in the treatment of majority of cancer types, this review will describe two areas of radiobiology, hyperfractionated and hypofractionated radiation therapy, for cancer treatment focusing on application of novel concepts underlying these treatment modalities. The initial part of the review discusses the phenomenon of hyper-radiation sensitivity (HRS) at lower doses (0.1 to 0.6 Gy), describing the underlying mechanisms and how this could enhance the effects of chemotherapy, particularly, in hyperfractionated settings. The second part examines the radiobiological/physiological mechanisms underlying the effects of high-dose hypofractionated radiation therapy that can be exploited for tumor cure. These include abscopal/bystander effects, activation of immune system, endothelial cell death and effect of hypoxia with re-oxygenation. These biological properties along with targeted dose delivery and distribution to reduce normal tissue toxicity may make high-dose hypofractionation more effective than conventional radiation therapy for treatment of advanced cancers. The novel radiation physics based methods that take into consideration the tumor volume to be irradiated and normal tissue avoidance/tolerance can further improve treatment outcome and post-treatment quality of life. In conclusion, there is enough evidence to further explore novel avenues to exploit biological mechanisms from hyper-fractionation by enhancing the efficacy of chemotherapy and hypo-fractionated radiation therapy that could enhance tumor control and use imaging and technological advances to reduce toxicity.
Low Doses Fractionated Radiation Therapy (LDFRT); hyper-radiation sensitivity (HRS); induced radiation resistance (IRR); hyperfractionation; chemopotentiation; stereotactic body radiation therapy (SBRT); stereotactic ablative radiosurgery (SARS); stereotactic ablative radiotherapy (SABR); stereotactic radiosurgery (SRS); spatially fractionated GRID radiotherapy (SFGRT); lattice
The addition of chemotherapeutic agents to ionizing radiation has improved survival in many malignancies. Cure rates may be further improved by adding novel targeted agents to current radiotherapy or radiochemotherapy regimens. Despite promising laboratory data, progress in the clinical development of new drugs with radiation has been limited. To define and address the problems involved, a collaborative effort between individuals within the translational research program of the Radiation Oncology Therapy Group and the National Cancer Institute was established. We discerned challenges to drug development with radiation including: 1) the limited relevance of preclinical work, 2) the pharmaceutical industry’s diminished interest, and 3) the important individual skills and institutional commitments required to ensure a successful program. The differences between early-phase trial designs with and without radiation are noted as substantial. The traditional endpoints for early-phase clinical trials—acute toxicity and maximum-tolerated dose—are of limited value when combining targeted agents with radiation. Furthermore, response rate is not a useful surrogate marker of activity in radiation combination trials.Consequently, a risk-stratified model for drug-dose escalation with radiation is proposed, based upon the known and estimated adverse effects. The guidelines discuss new clinical trial designs, such as the time-to-event continual reassessment method design for phase I trials, randomized phase II “screening” trials, and the use of surrogate endpoints, such as pathological response. It is hoped that by providing a clear pathway, this article will accelerate the rate of drug development with radiation.
Radiation oncology modalities such as intensity-modulated and image-guided radiation therapy can reduce the high dose to normal tissue and deliver a heterogeneous dose to tumors focusing on areas deemed at highest risk for tumor persistence. Clinical radiation oncology produces daily doses ranging from 1 to 20 Gy, with tissues being exposed to 30 or more daily fractions. Hypothesizing that cells that survive fractionated radiation therapy have a substantially different phenotype than the untreated cells, which might be exploitable for targeting with molecular therapeutics or immunotherapy, three prostate cancer cell lines (PC3, DU145 and LNCaP) and normal endothelial cells were studied to understand the biology of differential effects of multi-fraction (MF) radiation of 0.5, 1 and/or 2 Gy fraction to 10 Gy total dose, and a single dose (SD) of 5 and 10 Gy. The resulting changes in mRNA, miRNA and phosphoproteome were analyzed. Significant differences were observed in the MF radiation exposures including those from the 0.5 Gy MF that produces little cell killing. As expected, p53 function played a major role in response. Pathways modified by MF include immune response, DNA damage, cell cycle arrest, TGF-β, survival and apoptotic signal transduction. The radiation-induced stress response will set-forth a unique platform for exploiting the effects of radiation therapy as “focused biology” for cancer treatment in conjunction with molecular targeted or immunologically directed therapy. Given that more normal tissue is treated, albeit to lower doses with these newer techniques, the response of the normal tissue may also influence long-term treatment outcome.
Following the earthquake and tsunami in northern Japan on 11 March 2011, and the ensuing damage to the Fukushima Daiichi nuclear power plant complex, a request by the U.S. Ambassador to Japan to the U.S. Department of Health and Human Services (DHHS) Assistant Secretary for Preparedness and Response (ASPR) resulted in deployment of a five-person team of subject matter experts to the U.S. Embassy. The primary purpose of the deployment was to provide the U.S. Embassy in Tokyo with guidance on health and medical issues related to potential radiation exposure of U.S. citizens in Japan, including employees of the U.S. Department of State at consulates in Japan and American citizens living in or visiting Japan. At the request of the Government of Japan, the deployed health team also assisted Japanese experts in their public health response to the radiation incident. Over a three-week period in Japan and continuing for weeks after their return to the U.S., the team provided expertise in the areas of medical and radiation oncology, health physics, assessment of radiation dose and cancer risk, particularly to U.S. citizens living in Tokyo and the surrounding areas, food and water contamination and the acceptable limits, countermeasures to exposure such as potassium iodide (KI), the use of KI and an offered donation from the United States, evacuation and re-entry issues, and health/emergency-related communication strategies. This paper describes the various strategies used and observations made by the DHHS team during the first two months after the Fukushima crisis began.
public heath; emergency response; radiation exposure; medical countermeasures; nuclear power plant
We assessed changes in cell lines of varying p53 status after various fractionation regimens to determine if p53 influences gene expression and if multifractionated (MF) irradiation can induce molecular pathway changes. LNCaP (p53 wild-type), PC3 (p53 null), and DU145 (p53 mutant) prostate carcinoma cells received 5 and 10 Gy as single-dose (SD) or MF (0.5 Gy x 10, 1 Gy x 10, and 2 Gy x 5) irradiation to simulate hypofractionated and conventionally fractionated prostate radiotherapies, respectively. mRNA analysis revealed 978 LNCaP genes differentially expressed (greater than two-fold change, P < .05) after irradiation. Most were altered with SD (69%) and downregulated (75%). Fewer PC3 (343) and DU145 (116) genes were induced, with most upregulated (87%, 89%) and altered with MF irradiation. Gene ontology revealed immune response and interferon genes most prominently expressed after irradiation in PC3 and DU145. Cell cycle regulatory (P = 9.23 x 10-73, 14.2% of altered genes, nearly universally downregulated) and DNA replication/repair (P = 6.86 x 10-30) genes were most prominent in LNCaP. Stress response and proliferation genes were altered in all cell lines. p53-activated genes were only induced in LNCaP. Differences in gene expression exist between cell lines and after varying irradiation regimens that are p53 dependent. As the duration of changes is ≥24 hours, it may be possible to use radiation-inducible targeted therapy to enhance the efficacy of molecular targeted agents.
The authors look back at the five decades of radiation oncology and consider how one's choices and decisions influence how a career is pursued and how a professional life is lived.
Accomplishments and contributions in a career in radiation oncology, and in medicine in general, involve individual choices that impact the direction of a specialty, decisions in patient care, consequences of treatment outcome, and personal satisfaction. Issues in radiation oncology include: the development and implementation of new radiation treatment technology; the use of multimodality and biologically based therapies; the role of nonradiation “energy” technologies, often by other medical specialties, including the need for quality assurance in treatment and data reporting; and the type of evidence, including appropriate study design, analysis, and rigorous long-term follow-up, that is sought before widespread implementation of a new treatment. Personal choices must weigh: the pressure from institutions—practices, departments, universities, and hospitals; the need to serve society and the underserved; the balance between individual reward and a greater mission; and the critical role of personal values and integrity, often requiring difficult and “life-defining” decisions. The impact that each of us makes in a career is perhaps more a result of character than of the specific details enumerated on one's curriculum vitae. The individual tapestry weaved by choosing the more or less traveled paths during a career results in many pathways that would be called success; however, the one path for which there is no good alternative is that of living and acting with integrity.
Radiation oncology; Personalized medicine; Medical ethics; Medical technology
Non-steroidal anti-inflammatory drugs (NSAIDs) have come under scrutiny because of the gastrointestinal, renal and cardiovascular toxicity associated with prolonged use of these drugs. The purpose of this study was to identify molecular targets for NSAIDs related to cellular toxicity with a view to optimize drug efficacy in clinic. Coronary artery smooth muscle cells (CASMC) and endothelial cells (HCAEC) were treated with low (clinically achievable) and high (typically used in preclinical studies) concentrations of celecoxib (CXB), NS398 (NS) and ibuprofen (IBU) for 24h. NSAIDs-induced gene expression changes were evaluated by microarray analysis and validated by real-time RT-PCR and western blotting. The functional significance of differentially expressed genes was evaluated by Ingenuity Pathway Analysis (IPA). At high concentrations, NSAIDs altered the expression of genes regulating cell proliferation and cell death. NSAIDs also altered genes associated with cardiovascular functions including inflammation, thrombosis, fibrinolysis, coronary artery disease and hypertension. The gene expression was most impacted by IBU, CXB and NS, in that order. This study revealed that NSAIDs altered expression of an array of genes associated with cardiovascular events and emphasizes the potential for fingerprinting drugs in preclinical studies to assess the potential drug toxicity and to optimize the drug efficacy in clinical settings.
NSAIDs; HCAEC; CASMC; Microarray; Cardiovascular genes
On June 27–28, 2011 scientists from the National Cancer Institute (NCI), NASA, and academia met in Bethesda to discuss major lung cancer issues confronting each organization. For NASA – available data suggest lung cancer is the largest potential cancer risk from space travel for both men and women and quantitative risk assessment information for mission planning is needed. In space the radiation risk is from high energy and charge (HZE) nuclei (such as Fe) and high energy protons from solar flares and not from gamma radiation. By contrast the NCI is endeavoring to estimate the increased lung cancer risk from the potential wide-spread implementation of computed tomography (CT) screening in individuals at high risk for developing lung cancer based on the National Lung Cancer Screening Trial (NLST). For the latter, exposure will be x-rays from CT scans from the screening (which uses “low dose” CT scans) and also from follow-up scans used to evaluate abnormalities found during initial screening. Topics discussed included the risk of lung cancer arising after HZE particle, proton, and low dose Earth radiation exposure. The workshop examined preclinical models, epidemiology, molecular markers, “omics” technology, radiobiology issues, and lung stem cells (LSC) that relate to the development of lung cancer.
To describe the history, composition, and activities of the Radiation Injury Treatment Network (RITN). The Radiation Injury Treatment Network® is a cooperative effort of the National Marrow Donor Program and the American Society for Blood and Marrow Transplantation. The goals of RITN are to educate hematologists, oncologists, and stem cell transplant practitioners about their potential involvement in the response to a radiation incident and provide treatment expertise. Injuries to the marrow system readily occur when a victim is exposed to ionising radiation. This focus therefore leverages the expertise of these specialists who are accustomed to providing the intensive supportive care required by patients with a suppressed marrow function. Following a radiological incident, RITN centres may be asked to: Accept patient transfers to their institutions; provide treatment expertise to practitioners caring for victims at other centres; travel to other centres to provide medical expertise; or provide data on victims treated at their centres. Moving forward, it is crucial that we develop a coordinated interdisciplinary approach in planning for and responding to radiological and nuclear incidents. The ongoing efforts of radiation biologists, radiation oncologists, and health physicists can and should complement the efforts of RITN and government agencies.
RITN serves as a vital partner in preparedness and response efforts for potential radiological and nuclear incidents.
radiation accidents; cell therapy; haematology–radiation; radiation injury; emergency response; emergency preparedness
The biological characterization of an individual patient’s tumor by noninvasive imaging will have an important role in cancer care and clinical research if the molecular processes that underlie the image data are known. Spatial heterogeneity in the dynamics of magnetic resonance imaging contrast enhancement (DCE-MRI) is hypothesized to reflect variations in tumor angiogenesis. Here we demonstrate the feasibility of precisely colocalizing DCE-MRI data with the genomic and proteomic profiles of underlying biopsy tissue using a novel MRI-guided biopsy technique in patients with prostate cancer.
Angiogenesis; molecular imaging; interventional MRI; prostate cancer; micro-array analysis
We investigated the accuracy and feasibility of a system that provides transrectal needle access to the prostate concurrent with 1.5 Tesla MRI which previously has not been possible.
Materials and Methods
In 5 patients with previously diagnosed prostate cancer, MRI guided intraprostatic placement of gold fiducial markers (4 procedures) and/or prostate biopsy (3 procedures) was performed using local anesthesia.
Mean procedure duration was 76 minutes and all patients tolerated the intervention well. Procedure related adverse events included self-limited hematuria and hematochezia following 3 of 8 procedures (all resolved in less than 1 week). Mean needle placement accuracy was 1.9 mm for the fiducial marker placement studies and 1.8 mm for the biopsy procedures. Mean fiducial marker placement accuracy was 4.8 mm and the mean fiducial marker placement accuracy transverse to the needle direction was 2.6 mm. All patients who underwent the procedure were able to complete their course of radiotherapy without delay or complication.
While studies of clinical usefulness are warranted, transrectal 1.5 T MRI guided prostate biopsy and fiducial marker placement is feasible using this system, providing new opportunities for image guided diagnostic and therapeutic prostate interventions.
magnetic resonance imaging; prostate; prostatic neoplasms; biopsy; radiology; interventional
Purpose/Objective(s): American Indians (AIs) present with more advanced stages of cancer and, therefore, suffer from higher cancer mortality rates compared to non-AIs. Under the National Cancer Institute (NCI) Cancer Disparities Research Partnership (CDRP) Program, we have been researching methods of improving cancer treatment and outcomes since 2002, for AIs in Western South Dakota, through the Walking Forward (WF) Program. Materials/Methods: This program consists of (a) a culturally tailored patient navigation program that facilitated access to innovative clinical trials in conjunction with a comprehensive educational program encouraging screening and early detection, (b), surveys to evaluate barriers to access, (c) clinical trials focusing on reducing treatment length to facilitate enhanced participation using brachytherapy and intensity modulated radiotherapy (IMRT) for breast and prostate cancer, as AIs live a median of 140 miles from the cancer center, and (d) a molecular study (ataxia telangiectasia mutated) to address whether there is a specific profile that increases toxicity risks. Results: We describe the design and implementation of this program, summary of previously published results, and ongoing research to influence stage at presentation. Some of the critical outcomes include the successful implementation of a community-based research program, development of trust within tribal communities, identification of barriers, analysis of nearly 400 navigated cancer patients, clinical trial accrual rate of 10%, and total enrollment of nearly 2,500 AIs on WF research studies. Conclusion: This NCI funded pilot program has achieved some initial measures of success. A research infrastructure has been created in a community setting to address new research questions and interventions. Efforts underway to promote cancer education and screening are presented, as well as applications of the lessons learned to other health disparity populations – both nationally and internationally.
patient navigation; American Indians; cancer disparities; radiation oncology
Cyclooxygenase-2 (COX-2) plays a significant role in tumor development and progression. Nonsteroidal anti-inflammatory drugs (NSAIDs) exhibit potent anticancer effects in vitro and in vivo by COX-2 dependent and independent mechanisms. In this study, we used microarray analysis to identify the change of expression profile regulated by a COX-2 specific NSAID NS-398 (0.01 and 0.1mM), a non-specific NSAID ibuprofen (0.1 and 1.5mM) and RNA interference-mediated COX-2 inhibition (COX-2 RNAi) in PC3 prostate cancer cells. A total of 3,362 differentially expressed genes with 2 fold change, and p<0.05 were identified. Low concentrations of NSAIDs and COX-2 RNAi altered very few genes (1-3%) compared to the higher concentration of NS-398 (17%) and ibuprofen (80%). Ingenuity Pathway Analysis (IPA) was used for distributing the differentially expressed genes into biological networks and for evaluation of functional significance. The top 3 networks for the both NSAIDs included functional categories DNA replication, recombination and repair, and gastrointestinal disease. Immune response function was specific to NS-398, and cell cycle, cellular movement were among the top functions for ibuprofen. IPA also identified renal and urological disease as a function specific for ibuprofen. This comprehensive study identified several COX-2 independent targets of NSAIDs which may help explain the antitumor and radiosensitizing effects of NSAIDs. However, none of these categories were reflected in the identified networks in PC3 cells treated with clinically relevant low concentrations of NS-398 and ibuprofen or with COX-2 RNAi suggesting the benefit to fingerprinting pre-clinical drug concentrations to improve their relevance to the clinical setting.
microarray; NSAIDs; COX-2; NS-398; ibuprofen; COX-2 RNAi
A technique for transperineal high-dose-rate (HDR) prostate brachytherapy and needle biopsy in a standard 1.5 T MRI scanner is demonstrated. In each of eight procedures (in four patients with intermediate to high risk localized prostate cancer), four MRI-guided transperineal prostate biopsies were obtained followed by placement of 14–15 hollow transperineal catheters for HDR brachytherapy. Mean needle-placement accuracy was 2.1 mm, 95% of needle-placement errors were less than 4.0 mm, and the maximum needle-placement error was 4.4 mm. In addition to guiding the placement of biopsy needles and brachytherapy catheters, MR images were also used for brachytherapy treatment planning and optimization. Because 1.5 T MR images are directly acquired during the interventional procedure, dependence on deformable registration is reduced and online image quality is maximized.
MRI; brachytherapy; prostate; prostatic neoplasms; biopsy; interventional MRI
Cytidine deaminase, an enzyme that catalyses the deamination of both cytidine and its nucleoside analogues including the antineoplastic agents cytosine arabinoside (ara-C) and 5-azacytidine (5-azaC), has been partially purified from normal and leukemic human granulocytes. The purification procedure included heat precipitation at 70°C, ammonium sulfate precipitation, calcium phosphate gel ion exchange, and Sephadex G-150 gel filtration. The enzyme has mol wt 51,000, isoelectric pH of 4.8, and maximum activity over a broad pH range of 5-9.5. The enzyme is stabilized by the presence of the sulfhydryl reagent, dithiothreitol.
Cytidine deaminase from normal human granulocytes has a greater affinity for its physiologic substrate cytidine (Km = 1.1 × 10−5 M) than for ara-C (8.8 × 10−5 M) or 5-azaC (4.3 × 10−4 M). Halogenated analogues such as 5-fluorocytidine and 5-bromo-2′-deoxycytidine also exhibited substrate activity, with maximum velocities greater than that of the physiologic substrates cytidine and deoxycytidine. No activity was observed with nucleotides or deoxynucleotides. The relative maximum velocity of the enzyme for cytidine and its nucleoside analogues remained constant during purification, indicating that a single enzyme was responsible for deamination of these substrates.
Tetrahydrouridine (THU) was found to be a strong competitive inhibitor of partially purified deaminase with a Ki of 5.4 × 10−8 M.
The biochemical properties of partially purified preparations of cytidine deaminase from normal and leukemic cells were compared with respect to isoelectric pH, molecular weight, and substrate and inhibitor kinetic parameters, and no differences were observed. However, normal circulating granulocytes contained a significantly greater concentration of cytidine deaminase (3.52±1.86 × 103/mg protein) than chronic myelocytic leukemia (CML) cells (1.40±0.70 × 103 U/mg protein) or acute myelocytic leukemia (AML) cells (0.19±0.17 × 103 U/mg protein). To explain these differences in enzyme levels in leukemic versus normal cells, the changes in cytidine deaminase levels associated with maturation of normal granulocytes were studied in normal human bone marrow. Myeloid precursors obtained from bone marrow aspirates were separated into mature and immature fractions by Ficoll density centrifugation. Deaminase activity in lysates of mature granulocytes was 3.55-14.2 times greater than the activity found in the lysates of immature cells. Decreased enzyme activity was also found in immature myeloid cells from a patient with CML as compared to mature granulocytes from the same patient. These observations support the conclusion that the greater specific activity of cytidine deaminase in normal mature granulocytes as compared to leukemic cells is related to the process of granulocyte maturation rather than a specific enzymatic defect in leukemic cells.
In the context of national calls for reorganizing cancer clinical trials, the National Cancer Institute (NCI) sponsored a two day workshop to examine the challenges and opportunities for optimizing radiotherapy quality assurance (QA) in clinical trial design.
Participants reviewed the current processes of clinical trial QA and noted the QA challenges presented by advanced technologies. Lessons learned from the radiotherapy QA programs of recent trials were discussed in detail. Four potential opportunities for optimizing radiotherapy QA were explored, including the use of normal tissue toxicity and tumor control metrics, biomarkers of radiation toxicity, new radiotherapy modalities like proton beam therapy, and the international harmonization of clinical trial QA.
Four recommendations were made: 1) Develop a tiered (and more efficient) system for radiotherapy QA and tailor intensity of QA to clinical trial objectives. Tiers include (i) general credentialing, (ii) trial specific credentialing, and (iii) individual case review; 2) Establish a case QA repository; 3) Develop an evidence base for clinical trial QA and introduce innovative prospective trial designs to evaluate radiotherapy QA in clinical trials; and 4) Explore the feasibility of consolidating clinical trial QA in the United States.
Radiotherapy QA may impact clinical trial accrual, cost, outcomes and generalizability. To achieve maximum benefit, QA programs must become more efficient and evidence-based.
clinical trial design; credentialing; radiotherapy; quality assurance
Magnetic resonance imaging (MRI) provides superior visualization of the prostate and surrounding anatomy, making it the modality of choice for imaging the prostate gland. This pilot study was performed to determine the feasibility and dosimetric quality achieved when placing high-dose-rate prostate brachytherapy catheters under MRI guidance in a standard “closed-bore” 1.5T scanner.
Methods and Materials:
Patients with intermediate-risk and high-risk localized prostate cancer received MRI-guided high-dose-rate brachytherapy boosts before and after a course of external beam radiotherapy. Using a custom visualization and targeting program, the brachytherapy catheters were placed and adjusted under MRI guidance until satisfactory implant geometry was achieved. Inverse treatment planning was performed using high-resolution T2-weighted MRI.
Ten brachytherapy procedures were performed on 5 patients. The median percentage of volume receiving 100% of prescribed minimal peripheral dose (V100) achieved was 94% (mean, 92%; 95% confidence interval, 89–95%). The urethral V125 ranged from 0% to 18% (median, 5%), and the rectal V75 ranged from 0% to 3.1% (median, 0.3%). In all cases, lesions highly suspicious for malignancy could be visualized on the procedural MRI, and extracapsular disease was identified in 2 patients.
High-dose-rate prostate brachytherapy in a standard 1.5T MRI scanner is feasible and achieves favorable dosimetry within a reasonable period with high-quality image guidance. Although the procedure was well tolerated in the acute setting, additional follow-up is required to determine the long-term safety and efficacy of this approach.
Prostate cancer; Brachytherapy; MRI; Image guidance
To test whether intrarectal Amifostine limits symptoms of radiation proctitis as measured by the RTOG GI toxicity score and the expanded prostate cancer index composite (EPIC) score.
Methods and Materials
Patients with localized prostate cancer recieved Amifostine as a rectal suspension 30–45 min before daily 3D-conformal radiation treatments (3D-CRT). The first 18 patients received 1gm of Amifostine and the next 12 patients received 2gm. Toxicity was assessed at baseline, during treatment, and at follow-up visits using RTOG grading and the EPIC Quality of Life (QoL) 50 item questionnaire. The “Bowel Function” subset of the bowel domain (EPIC-BF), which targets symptom severity, and “Bowel Bother” subset of the bowel domain (EPIC-BB), which assesses quality of life, were evaluated and compared to the RTOG GI toxicity score.
Median follow-up was 30 months (range 18–36). Overall, the EPIC-BF and EPIC-BB scores both track closely with the RTOG GI toxicity score. Seven weeks after the start of radiation therapy, the incidence of RTOG Grade 2 toxicity was 33% in the 1gm group (6/18) compared with 0% (0/12) in the 2gm group and trended towards statistical significance (p=0.06). A significant difference between Amifostine groups was observed using the EPIC-BF score at 7 weeks (p=0.04). A difference in EPIC-BB score between dose groups was evident at 7 weeks (p=0.07) and was significant at 12 months (p=0.04).
Higher doses of Amifostine produce significant improvements in acute and late bowel QoL (up to one year following therapy) as measured by the EPIC score.
Amifostine; Prostate; Radiation-induced Proctitis; EPIC; Quality of Life
To report early observation of transient PSA elevations on this pilot study of external beam radiation therapy and magnetic resonance imaging (MRI) guided high dose rate (HDR) brachytherapy boost.
Materials and methods
Eleven patients with intermediate-risk and high-risk localized prostate cancer received MRI guided HDR brachytherapy (10.5 Gy each fraction) before and after a course of external beam radiotherapy (46 Gy). Two patients continued on hormones during follow-up and were censored for this analysis. Four patients discontinued hormone therapy after RT. Five patients did not receive hormones. PSA bounce is defined as a rise in PSA values with a subsequent fall below the nadir value or to below 20% of the maximum PSA level. Six previously published definitions of biochemical failure to distinguish true failure from were tested: definition 1, rise >0.2 ng/mL; definition 2, rise >0.4 ng/mL; definition 3, rise >35% of previous value; definition 4, ASTRO defined guidelines, definition 5 nadir + 2 ng/ml, and definition 6, nadir + 3 ng/ml.
Median follow-up was 24 months (range 18–36 mo). During follow-up, the incidence of transient PSA elevation was: 55% for definition 1, 44% for definition 2, 55% for definition 3, 33% for definition 4, 11% for definition 5, and 11% for definition 6.
We observed a substantial incidence of transient elevations in PSA following combined external beam radiation and HDR brachytherapy for prostate cancer. Such elevations seem to be self-limited and should not trigger initiation of salvage therapies. No definition of failure was completely predictive.