Bone metastases are a common feature of advanced genitourinary malignancies and a prominent cause of morbidity and mortality. Clinical manifestations can include pain, hypercalcemia, pathologic fractures, and spinal cord compression. Optimal systemic therapy for the skeletal component of these cancers often features a combination of disease-specific therapy and bone-targeted therapy. Some agents such as the radiopharmaceutical radium-223 blur the line between those two categories. Osteoclast inhibition is a validated strategy in the management of selected patients with bone metastases and can best be accomplished with one of two agents. Zoledronic acid is the most potent available bisphosphonate and is approved for the prevention of skeletal events due to solid tumors metastatic to bone. Denosumab is a fully human monoclonal antibody that binds and inactivates receptor activator of nuclear factor-kappa-B ligand and is approved for the same indication. Radiopharmaceuticals represent a distinct strategy. Beta-emitters such as strontium-89 and samarium-153 can be effective for the palliation of pain due to bone metastases, but their use is often limited by bone marrow suppression. The alpha-emitting radiopharmaceutical radium-223 has recently been shown to improve overall survival and prevent skeletal events in selected men with castration-resistant prostate cancer metastatic to bone. Multiple ongoing clinical trials are designed to examine the potential for therapeutic inhibition of additional targets such as Src and hepatocyte growth factor (MET). This review discusses the incidence, pathophysiology, and management of bone metastases in the most prevalent genitourinary malignancies.
Abiraterone acetate, an androgen biosynthesis inhibitor, improves overall survival (OS) in metastatic castration-resistant prostate cancer (mCRPC) post-chemotherapy. Many mCRPC patients never receive chemotherapy and thus cannot benefit from abiraterone acetate; we evaluated this agent in mCRPC patients who had not received chemotherapy.
In this double-blind study, 1088 patients were randomized 1:1 to abiraterone acetate (1000 mg) plus prednisone (5 mg twice daily) or placebo plus prednisone. Co-primary end points were radiographic progression-free survival (rPFS) and OS. Secondary end points measured clinically relevant landmarks of mCRPC progression. Patient-reported outcomes included pain progression and quality of life.
The study was unblinded after a planned interim analysis (IA) at 43% of OS events. Treatment with abiraterone acetate-prednisone resulted in a 57% reduction in the risk of radiographic progression or death (hazard ratio [HR], 0.43; 95% confidence interval [CI]: 0.35 to 0.52; P<0.001; 13% OS events IA) and an estimated 25% decrease in the risk of death (HR, 0.75; 95% CI: 0.61 to 0.93; P=0.009; 43% OS events IA). Secondary end points supported superiority of abiraterone acetate-prednisone: time to cytotoxic chemotherapy initiation, opiate use for cancer-related pain, prostate-specific antigen progression (all P<0.001) and performance status deterioration (P=0.005). Self-reported time to pain progression and patient functional status degradation favored abiraterone acetate-prednisone (P=0.05 and P=0.003). Grade 3/4 mineralocorticoid-related adverse events and liver function test abnormalities were more common with abiraterone acetate-prednisone.
Abiraterone acetate produces OS and rPFS benefits, as well as significant delays in clinical deterioration and initiation of chemotherapy, in mCRPC.
Abiraterone acetate; prednisone; metastatic castration-resistant prostate cancer; androgen; CYP17
Our objective is to assess differences in practice patterns and outcomes across 3 regions in bladder cancer patients treated with radical cystectomy under a universal healthcare system.
In total, we included 2287 patients treated with radical cystectomy at 8 Canadian centres from 1998 to 2008. Variables included various clinico-pathologic parameters, recurrence, and death stratified into different regions.
In total, 1105 patients were from the east region (group 1), 601 from the centre region (group 2), and 581 from the west region of Canada (group 3). The median follow-up of groups 1, 2, and 3 was 22.1, 17.1, and 28.6 months, respectively. Although the overall rate of neoadjuvant chemotherapy was low (3.1%), rates were higher in group 2 compared with groups 1 and 3 (p = 0.07). Continent diversions and extended lymphadenectomy were performed in 23.5%, 8.5%, 23.9% and 39.7%, 27.7%, 12.6% across groups 1, 2, and 3, respectively. There were statistically significant differences in gender distribution, performance of lymphadenectomy, presence of concomitant carcinoma in situ and lymphovascular invasion across the 3 groups. There were no differences among the 3 geographical locations in terms of stage, surgical margin status, and use of adjuvant chemotherapy. The mean number of days from the transurethral resection of the bladder tumour to cystectomy was 50, 79, 69 days for groups 1, 2, 3, respectively (p = 0.0006). The 5-year overall survival was 53.6%, 66.8%, and 52.4% for groups 1, 2 and 3, respectively (p < 0.0001).
Significant variations in practice patterns were noted across different geographic regions in a universal healthcare system. Use of continent diversions, extended lymphadenectomy, and neoadjuvant chemotherapy remains low across all 3 regions. Treatment delays are significant.
Well-characterized, high-quality fresh-frozen prostate tissue is required for prostate cancer research. As part of the PROCURE Prostate Cancer Biobank launched in 2007, four University Hospitals in Quebec joined to bank fresh frozen prostate tissues from radical prostatectomies (RP). As the biobank progressed towards allocation, the nature and quality of the tissues were determined. RP tissues were collected by standardized alternate mirror-image or biopsy-based targeted methods, and frozen for banking. Clinical/pathological parameters were captured. For quality control, two presumed benign and two presumed cancerous frozen, biobanked tissue blocks per case (10/site) were randomly selected during the five years of collection. In a consensus meeting, 4 pathologists blindly evaluated slides (n=160) and graded quality, Gleason score (GS), and size of cancer foci. The quality of tissue RNA (37/40 cases) was assessed using the RNA Integrity Number. The biobank included 1819 patients of mean age: 62.1 years; serum PSA: 8ng/ml; prostate weight: 47.8 g; GS: 7; and pathological stage: T2 in 64.5%, T3A in 25.5% and T3B in 10% of cases. Of the 157 evaluable slides, 79 and 78 had benign and cancer tissue, respectively. GS for the 37 cancer-positive cases were: 6 in 9, 7 in 18 and >7 in 10 and, in most instances, in concordance with final GS. In 40% of slides containing cancer, foci occupied ≥50% of block surface and 42% had a diameter ≥1 cm. Tissue was well preserved and consistently yielded RNA of very good quality with RNA Integrity Number (RIN) >7 for 97% of cases (mean=8.7±0.7) during the five-year collection period. This study confirms the high quality of randomly selected benign and cancerous fresh-frozen prostate tissues of the PROCURE Quebec Prostate Cancer Biobank. These results strengthen the uniqueness of this large prospective resource for prostate cancer research.
To characterize changes in lean body mass (LBM) in men with prostate cancer receiving androgen-deprivation therapy (ADT).
Patients and Methods
We prospectively evaluated LBM in a prespecified substudy of a randomized controlled trial of denosumab to prevent fractures in men receiving ADT for nonmetastatic prostate cancer. LBM was measured by total-body dual-energy x-ray absorptiometry at study baseline and at 12, 24, and 36 months. The analyses included 252 patients (132, denosumab; 120, placebo) with a baseline and at least one on-study LBM assessment. Patients were stratified by age (< 70 v ≥ 70 years) and by ADT duration (≤ 6 v > 6 months).
Median ADT duration was 20.4 months at study baseline. Mean LBM decreased significantly from baseline, by 1.0% at month 12 (95% CI, 0.4% to 1.5%; P < .001; n = 248), by 2.1% at month 24 (95% CI, 1.5% to 2.7%; P < .001; n = 205), and by 2.4% at month 36 (95% CI, 1.6% to 3.2%; P < .001; n = 168). Men age ≥ 70 years (n = 127) had significantly greater changes in LBM at all measured time points than younger men. At 36 months, LBM decreased by 2.8% in men age ≥ 70 years and by 0.9% in younger men (P = .035). Men with ≤ 6 months of ADT at study entry (n = 36) had a greater rate of decrease in LBM compared with men who had received more than 6 months of ADT at study entry (3.7% v 2.0%; P = .0645).
In men receiving ADT, LBM decreased significantly after 12, 24, and 36 months.
Men with prostate cancer are at risk of experiencing accelerated bone loss and fractures as a result of androgen deprivation therapy (ADT).
We evaluated the effects of denosumab, a fully human monoclonal antibody against RANKL, on preservation of BMD at 3 key skeletal sites (lumbar spine [LS], femoral neck [FN], and total hip [TH]) and the distal radius at 36 months both by responder category and individual responses in a waterfall plot analysis.
Design, Setting, and Participants
This phase 3, randomized, double-blind study of men with non-metastatic prostate cancer receiving ADT investigated the effects of denosumab on bone mineral density (BMD) and fractures. Patients were treated for 36 months.
Subcutaneous denosumab 60 mg (n=734) or placebo (n=734) every 6 months for up to 36 months. Patients were instructed to take supplemental Calcium and vitamin D.
Primary outcome measure: The percentage change from baseline to month 36 in LS, FN, and TH BMD was measured by dual energy x-ray absorptiometry. BMD at the distal 1/3 radius at 36 months was measured in a sub-study of 309 patients.
Results and Limitations
At 36 months, significantly more patients in the denosumab arm had increases of >3% BMD from baseline at each site studied compared with placebo (LS, 78% vs 17%; TH, 48% vs 6%; FN, 48% vs 13%; distal 1/3 radius, 40% vs 7%). The percentage of denosumab patients with bone loss at all 3 key BMD sites at month 36 was 1%, as opposed to 42% in placebo arm. At 36 months 69% of denosumab-treated patients had BMD increases at all three sites (LS, TH or FN) compared with 8% of placebo-treated patients. Lower baseline BMD was associated with higher magnitude lumbar spine, femoral neck, and total hip BMD responses to denosumab.
In men with prostate cancer receiving ADT significantly higher BMD response rates were observed with denosumab vs. placebo.
This study is registered with ClinicalTrials.gov with the identifier NCT00089674.
androgen deprivation; bone mineral density; bone loss; antiresorptive therapy; responder analysis
The treatment of metastatic castrate-resistant prostate cancer (mCRPC) has evolved rapidly with the recent approval of a number of treatments and agents, including docetaxel, sipuleucel T, abiraterone, cabazitaxel, and enzalutamide. Enzalutamide (previously MDV-3100) is a novel oral androgen receptor inhibitor that targets multiple steps in the androgen receptor signaling pathway. The randomized phase III AFFIRM study demonstrated significant improvements in a number of efficacy endpoints, including the primary endpoint of overall survival and secondary endpoints of progression-free survival, and time to prostate-specific antigen progression in patients with progressive mCRPC who had received prior treatment with docetaxel. Enzalutamide was well tolerated and there were comparable incidences of grade 3 or greater adverse events reported for the enzalutamide and placebo control arms in AFFIRM. Unlike some other treatments for mCRPC, enzalutamide does not require administration with steroids. The ongoing randomized phase III PREVAIL trial will investigate the efficacy and safety of enzalutamide in chemotherapy-naïve patients with mCRPC. Additional trials are investigating the use of enzalutamide in a number of disease settings.
AFFIRM trial; enzalutamide; metastatic castrate resistant prostate cancer; PREVAIL trial
Elevated levels of clusterin (CLU), a stress-induced and secreted cytoprotective chaperone, are associated with advanced tumor stage, metastasis, treatment resistance, and adverse outcome in several cancers. Custirsen, a second-generation antisense oligonucleotide, inhibits CLU production in tumor cells and reduces serum CLU levels. A Phase 2 study evaluated custirsen in combination with second-line chemotherapy in men with metastatic castration-resistant prostate cancer (mCRPC) who had progressed while on or within 6 months of first-line docetaxel-based chemotherapy. Exploratory analyses evaluated serum CLU levels during custirsen treatment and correlative clinical effects on prostate-specific antigen (PSA) response, overall survival, and any relationship between serum CLU and PSA. Men with mCRPC were treated with mitoxantrone/prednisone/custirsen (MPC, n = 22) or docetaxel retreatment/prednisone/custirsen (DPC plus DPC-Assigned, n = 45) in an open-label, multicenter study. Subject-specific profiles of PSA and serum CLU levels during treatment were characterized using statistical modeling to compute subject-specific summary measures; these measures were analyzed for relationship to survival using proportional hazard regression. Estimated individual serum CLU response profiles were scored as below or at/above the median level for the population through 100 days postrandomization. Median survival was longer for subjects scoring below the median serum CLU level compared with subjects at/above the median level, respectively (MPC: 15.1 months vs. 6.2 months; DPC-Pooled: 17.0 months vs. 12.1 months). Lowered serum CLU levels during custirsen treatment when in combination with either chemotherapy regimen were predictive of longer survival in mCRPC. These results support further evaluation of serum CLU as a therapeutic biomarker.
Aside from PSA, there are currently no other prognostic or predictive biomarkers that can be used to guide treatment response in metastatic castration resistant prostate cancer (mCRPC). In a Phase 2 study, men with mCRPC were treated with prednisone and custirsen plus either mitoxantrone or docetaxel retreatment. Statistical modeling was used to compute subject-specific summary measures of PSA and serum clusterin levels at baseline and at Day 100 of treatment, followed by a regression analysis to evaluate relationship to overall survival. In this analysis, reduced serum clusterin levels during treatment were predictive of longer survival. These results currently support further evaluation of serum clusterin as a therapeutic biomarker in three ongoing Phase 3 clinical trials.
Antisense oligonucleotide; chemotherapy; clusterin; custirsen; mCRPC
Bone metastases are a major cause of morbidity and mortality in men with prostate cancer. Preclinical studies suggest that osteoclast inhibition may prevent bone metastases. This phase 3 study evaluated denosumab, a fully human anti-RANKL monoclonal antibody, to prevent bone metastasis or death from any cause in men with non-metastatic castration-resistant prostate cancer (CRPC).
Men with non-metastatic CRPC at high risk for bone metastasis (PSA ≥8.0 ng/mL and/or PSA doubling time ≤10.0 months) were enrolled in 319 centers from 30 countries. Patients were randomised 1:1 in blinded fashion using an interactive voice response system to receive monthly subcutaneous denosumab 120 mg or placebo. The primary endpoint was bone metastasis-free survival, a composite endpoint determined by time to first occurrence of bone metastasis (symptomatic or asymptomatic) or death.
1432 patients were randomised, 716 to receive denosumab and 716 to receive placebo. Denosumab significantly increased bone metastasis-free survival by a median of 4.2 months over placebo (hazard ratio 0.85 [0.73–0.98]; P=0.028). Denosumab also significantly delayed time to first bone metastasis (hazard ratio 0.84 [0.71–0.98]; P=0.032). Overall survival was similar between groups (hazard ratio 1.01 [0.85–1.20]; P=0.91). Rates of adverse events (AEs) and serious AEs were generally similar between groups, except for osteonecrosis of jaw (ONJ) and hypocalcemia. Yearly cumulative incidence of ONJ for denosumab was: 1%, 3%, 4% in years 1, 2, 3, respectively; overall, less than 5% (n=33). Hypocalcemia occurred in under 2% (n=12) of denosumab and under 1% (n=2) of placebo patients. The blinded treatment phase has been completed.
In men with CRPC, denosumab significantly prolonged bone metastasis-free survival and delayed time to bone metastasis. This is the first large randomised study to demonstrate that targeting the bone microenvironment prevents bone metastasis in men with prostate cancer.
urology/prostate disease; denosumab; prostate cancer; prevention; bone metastasis; survival; hormone refractory; castration-resistant
The prognostic role, in terms of the overall survival outcome, of serum parathyroid hormone evaluated at baseline and after 3 months of zoledronic acid or placebo treatment in hormone-refractory prostate cancer patients with bone metastases enrolled in a randomized clinical trial was assessed.
Secondary hyperparathyroidism is frequent in prostate cancer patients with bone metastases, and this condition is worsened by the administration of potent bisphosphonates. Serum parathyroid hormone (PTH) elevation can impair the efficacy of these drugs in terms of survival.
The prognostic role of elevated serum PTH levels at baseline and after 3 months of zoledronic acid administration was assessed prospectively in 643 bone metastatic prostate cancer patients enrolled in a prospective randomized, placebo-controlled study.
On multivariate analysis, after adjusting for major prognostic factors and bone turnover markers, elevated baseline serum PTH level was negatively associated with overall survival (hazard ratio [HR], 1.448; 95% confidence interval [CI], 1.045–2.006; p < .03) in zoledronic acid–treated patients but not in placebo-treated patients. In patients with normal baseline PTH levels, there was a trend but insignificant association between zoledronic acid administration and a better survival outcome than with placebo (HR, 0.81; 95% CI, 0.65–1.01; p = .065), whereas a trend in the opposite direction was observed in patients with elevated PTH levels (HR, 1.45; 95% CI, 0.87–2.39; p = .151); interaction test, p = .040. Elevated serum PTH level after 3 months of zoledronic acid treatment was not significantly associated with survival outcome.
Secondary hyperparathyroidism has a negative prognostic impact in metastatic prostate cancer patients undergoing zoledronic acid administration. Counteracting elevated PTH levels by adequate doses of vitamin D may improve the efficacy of this drug.
Bone metastasis; Parathyroid hormone; Prostate cancer; Zoledronic acid
Intermittent androgen deprivation for prostate-specific antigen (PSA) elevation after radiotherapy may improve quality of life and delay hormone resistance. We assessed overall survival with intermittent versus continuous androgen deprivation in a noninferiority randomized trial.
We enrolled patients with a PSA level greater than 3 ng per milliliter more than 1 year after primary or salvage radiotherapy for localized prostate cancer. Intermittent treatment was provided in 8-month cycles, with nontreatment periods determined according to the PSA level. The primary end point was overall survival. Secondary end points included quality of life, time to castration-resistant disease, and duration of nontreatment intervals.
Of 1386 enrolled patients, 690 were randomly assigned to intermittent therapy and 696 to continuous therapy. Median follow-up was 6.9 years. There were no significant between-group differences in adverse events. In the intermittent-therapy group, full testosterone recovery occurred in 35% of patients, and testosterone recovery to the trial-entry threshold occurred in 79%. Intermittent therapy provided potential benefits with respect to physical function, fatigue, urinary problems, hot flashes, libido, and erectile function. There were 268 deaths in the intermittent-therapy group and 256 in the continuous-therapy group. Median overall survival was 8.8 years in the intermittent-therapy group versus 9.1 years in the continuous-therapy group (hazard ratio for death, 1.02; 95% confidence interval, 0.86 to 1.21). The estimated 7-year cumulative rates of disease-related death were 18% and 15% in the two groups, respectively (P = 0.24).
Intermittent androgen deprivation was noninferior to continuous therapy with respect to overall survival. Some quality-of-life factors improved with intermittent therapy. (Funded by the Canadian Cancer Society Research Institute and others; ClinicalTrials.gov number, NCT00003653.)
Whereas prostate cancer was once deemed unresponsive to chemotherapy, there is now evidence that patients with metastatic castration-resistant prostate cancer can obtain a survival benefit from both first-line (docetaxel-based) and second-line (cabazitaxel-based) chemotherapy. The side effects of these agents have been shown to be predictable and manageable, particularly in North American centres. However, patient selection remains a key issue, with the aim of delivering each line of treatment at a time when the individual patient remains fit and well enough to tolerate a cytotoxic regimen. Hence, it is increasingly important for urologists and oncologists to work together to ensure timely consideration of the chemotherapeutic approach before it is precluded by a decline in performance status.
The emergence of chemotherapy as a survival-improving treatment for metastatic castration-resistant prostate cancer has focused attention on the need for effective prevention and management of side effects. The most recent chemotherapeutic agent in this setting is cabazitaxel, licensed for use when the disease progresses on or after docetaxel-based treatment. Experience with cabazitaxel shows that, as with docetaxel, its side effects are largely predictable and manageable using methods that are already well-known to oncology teams. Patient education, clear instructions for when and how patients should seek advice, and properly implemented local policies on side effect management are essential to optimal patient care.
Androgen deprivation therapy (ADT) for prostate cancer increases fracture risk, decreases bone mineral density, and increases bone turnover markers (BTMs) including serum type 1 C-telopeptide (sCTX), tartrate-resistant alkaline phosphatase 5b (TRAP-5b), and procollagen-1 N-terminal telopeptide (P1NP). In a pre-specified exploratory analysis of a phase 3, multicenter, double-blind study, we evaluated the effects of denosumab (60 mg subcutaneously every 6 months for 3 years) vs. placebo (1468 patients, 734 in each group) on BTM values. BTMs were measured at baseline, month 1, and pre-dose at months 6, 12, 24, and 36 in the overall population. BTMs at month 1 are also reported for subgroups based on age (<70 years vs. ≥ 70 years), prior duration of ADT (≤6 months vs. >6 months), and baseline BTM (≤ median vs. >median BTM values). Treatment with denosumab provided a rapid and sustained decrease of BTM values compared with placebo. The median change in sCTX levels at month 1 was −90% in the denosumab group and −3% in the placebo group (p <.0001). The median change in TRAP-5b levels at month 1 was −55% in the denosumab group and −3% in the placebo group (p <.0001). The maximal median change in P1NP was −64% in the denosumab group and −11% in the placebo group, (p <.0001). Significantly greater decreases in BTM for denosumab were also seen in subgroup analyses based on age, prior ADT treatment, and baseline BTM values. Suppression of bone turnover markers was consistent with marked increases in bone mineral density reported previously.
(5) denosumab; androgen deprivation therapy; bone turnover markers; prostate cancer
We delineated Canadian regional differences in practice patterns in the management of upper tract urothelial carcinoma (UTUC) after nephroureterectomy and relate these to patient outcomes.
A database was created with 1029 patients undergoing radical nephroureterectomy for UTUC between 1994 and 2009 at 10 Canadian centres. Demographic, clinical and pathological variables were collected from chart review. Practice pattern variables were defined as: open versus laparoscopic nephroureterectomy, management strategy for the distal ureter, performance of lymphadenectomy and administration of chemotherapy and/or radiation therapy. The outcome measures were overall (OS), disease-specific (DSS) and recurrence-free survival (RFS). The centres were divided into three regions (West, Central, East). Cox proportional multivariable linear regression analysis was used to determine the association between regional differences in practice patterns and clinical outcomes.
There was a significant difference in practice patterns between regions within Canada for: time from diagnosis to surgery (p = 0.001), type of surgery (open vs. laparoscopic, p < 0.01) and method of management of the distal ureter (p = 0.001). As well, there were significant differences in survival between regions across Canada: 5-year OS (West 70%, Central 81% and East 62%, p < 0.0001) and DSS (West=79%, Central=85%, East=75%, p = 0.007) were significantly different, but there was no difference in RFS (West 47%, Central 48%, East 46%, p = 0.88). Multivariable linear regression analysis demonstrated that the differences in survival were independent of region OS (p = 0.78), DSS (p = 0.30) or RFS (p = 0.43).
There is significant disparity in practice patterns between regions within Canada, but these do not appear to have an effect on survival. We believe that the variability in practice is a reflection of the lack of standardized treatments for UTUC and underlines the need for multi-institutional studies in this disease.
Skeletal-related events (SREs) are a common complication of bone metastases, and have serious negative consequences for patients with castrate-resistant prostate cancer (CRPC). SREs can lead to severe pain, increased risk of death, increased health care costs and reduced quality of life. Until recently, zoledronic acid has been the sole standard of care for the prevention of SREs in men with CRPC with bone metastases. Denosumab, a receptor activator of nuclear factor kappa-B ligand (RANK-L) inhibitor, has been recently approved for use in Canada for this indication, thus presenting another option for these patients. Denosumab was shown to be superior to zoledronic acid in delaying the time to first or subsequent SREs in CRPC patients with bone metastases. This review discusses current and previous trials examining agents designed to prevent SREs in men with CRPC and bone metastases. It also discusses the practical aspects of administering a bone-targeted therapy, including choosing a bone-targeted therapy, monitoring at the onset and during therapy, switching from one therapy to another, and assessing potential complications.
Biosynthesis of extragonadal androgen may contribute to the progression of castration-resistant prostate cancer. We evaluated whether abiraterone acetate, an inhibitor of androgen biosynthesis, prolongs overall survival among patients with metastatic castration-resistant prostate cancer who have received chemotherapy.
We randomly assigned, in a 2:1 ratio, 1195 patients who had previously received docetaxel to receive 5 mg of prednisone twice daily with either 1000 mg of abiraterone acetate (797 patients) or placebo (398 patients). The primary end point was overall survival. The secondary end points included time to prostate-specific antigen (PSA) progression (elevation in the PSA level according to prespecified criteria), progression-free survival according to radiologic findings based on prespecified criteria, and the PSA response rate.
After a median follow-up of 12.8 months, overall survival was longer in the abiraterone acetate–prednisone group than in the placebo–prednisone group (14.8 months vs. 10.9 months; hazard ratio, 0.65; 95% confidence interval, 0.54 to 0.77; P<0.001). Data were unblinded at the interim analysis, since these results exceeded the preplanned criteria for study termination. All secondary end points, including time to PSA progression (10.2 vs. 6.6 months; P<0.001), progression-free survival (5.6 months vs. 3.6 months; P<0.001), and PSA response rate (29% vs. 6%, P<0.001), favored the treatment group. Mineralocorticoid-related adverse events, including fluid retention, hypertension, and hypokalemia, were more frequently reported in the abiraterone acetate–prednisone group than in the placebo–prednisone group.
The inhibition of androgen biosynthesis by abiraterone acetate prolonged overall survival among patients with metastatic castration-resistant prostate cancer who previously received chemotherapy. (Funded by Cougar Biotechnology; COU-AA-301 ClinicalTrials.gov number, NCT00638690.)
Disrupted skeletal homeostasis is common in patients with prostate cancer. Low bone density is common at diagnosis, and fracture risk is further elevated by the effects of androgen-deprivation therapy. Later in the disease course, bone metastases can result in skeletal morbidity. Although prostate-specific antigen (PSA) levels can provide important insights into overall disease progression, convenient, noninvasive tools for monitoring skeletal health are lacking. Biochemical markers released into serum and urine as a result of bone turnover might fulfill this unmet need. The objectives of this article are to assess current evidence examining the potential utility of bone turnover markers for monitoring skeletal health. bone disease progression, and response to antiresorptive therapies in the prostate cancer setting.
Published articles and abstracts from major oncology or urology congresses pertaining to the use of bone turnover markers to monitor skeletal health and disease progression were identified and assessed for relevance and methodologic stringency.
Several randomized trials and correlative studies support the utility of bone marker level changes to assess disease progression in the metastatic setting, bone health during hormonal therapy, and response to bisphosphonate therapy. The available data support potential associations between levels of the collagen type I telopeptides (NTX and CTX) and the severity of metastatic bone disease as well as outcomes during antiresorptive therapy. Evidence linking bone marker level changes with early diagnosis of skeletal metastases is emerging. Although several markers have shown promising results in correlative studies, results from ongoing prospective trials are needed to establish the role of bone markers in this setting.
Bone marker levels reflect ongoing skeletal metabolism and can provide important insights into bone health and response to bisphosphonate therapy in patients with prostate cancer. The data supporting a role for bone markers to monitor skeletal disease progression and response to zoledronic acid therapy are especially strong. Bone marker assessments may complement established diagnostic and monitoring paradigms in prostate cancer.
Bisphosphonate; Bone loss; Bone metastases; Bone mineral density; Bone turnover markers; Prostate cancer
Many patients with advanced genitourinary malignancies develop bone metastases, which can lead to potentially debilitating skeletal complications. Moreover, age-related bone loss and cancer treatments such as hormonal therapy for prostate cancer can weaken bone, placing patients at risk for osteoporotic fractures in addition to skeletal-related events (SREs) from bone metastases. Zoledronic acid, a bisphosphonate, is approved worldwide to reduce the risk of SREs in patients with bone metastases from solid tumors or bone lesions from multiple myeloma. Zoledronic acid, although underutilized in genitourinary malignancies, has long been the mainstay of treatment in patients with bone metastases, and can also help preserve bone during anticancer therapy. Recently, denosumab, a monoclonal antibody directed against the receptor activator of nuclear factor kappa-B ligand, was approved in the United States and the European Union for reducing the risk of SREs in patients with bone metastases from solid tumors. Denosumab (at a lower dose) is also approved in the European Union and the United States to treat androgen deprivation-induced bone loss in men with prostate cancer. In addition, preclinical rationale and emerging clinical data suggest that bone-modifying agents may be able to delay disease progression in genitourinary cancers, just as newly developed anticancer treatments have produced reductions in SREs, possibly by indirect effects on the disease course. This review article summarizes current data and ongoing studies to preserve bone health in patients with advanced genitourinary cancers.
bisphosphonate; bone metastases; genitourinary cancer; prostate cancer; zoledronic acid
Malignant bone disease is common in patients with advanced solid tumors or multiple myeloma. Bisphosphonates have been found to be important treatments for bone metastases. A positive benefit-risk ratio for bisphosphonates has been established, and ongoing clinical trials will determine whether individualized therapy is possible.
Bisphosphonates are important treatments for bone metastases. Considerations for optimizing the clinical benefits of bisphosphonates include efficacy, compliance, and safety. Several bisphosphonates are approved for clinical use; however, few have demonstrated broad efficacy in the oncology setting and been compared directly in clinical trials. Among patients with bone metastases from breast cancer, the efficacy of approved bisphosphonates was evaluated in a Cochrane review, showing a reduction in the risk of skeletal-related events (SREs) ranging from 8% to 41% compared with placebo. Between-trial comparisons are confounded by inconsistencies in trial design, SRE definition, and endpoint selection. Zoledronic acid has demonstrated clinical benefits beyond those of pamidronate in a head-to-head trial that included patients with breast cancer or multiple myeloma. Compliance and adherence also have effects on treatment efficacy. In a comparison study, the adherence rates with oral bisphosphonates were found to be significantly lower compared with those of intravenous bisphosphonates. The safety profiles of oral and intravenous bisphosphonates differ. Oral bisphosphonates are associated with gastrointestinal side effects, whereas intravenous bisphosphonates have dose- and infusion rate–dependent effects on renal function. Osteonecrosis of the jaw is an uncommon but serious event in patients receiving monthly intravenous bisphosphonates or denosumab. The incidence of this event can be reduced with careful oral hygiene. A positive benefit-risk ratio for bisphosphonates has been established, and ongoing clinical trials will determine whether individualized therapy is possible.
Bisphosphonates; Neoplasm metastasis; Skeleton; Therapeutics
Atrasentan is a potent, oral, selective endothelin-A (ETA) receptor antagonist with clinical activity in patients with hormone-refractory prostate cancer (HRPC). This reports the results of a Phase 3, randomized, double-blind, placebo-controlled trial of atrasentan in patients with nonmetastatic HRPC.
Of 941 patients with adequate androgen suppression, no radiographic evidence of metastases but rising prostate-specific antigen (PSA) levels 467 received atrasentan 10 mg daily and 474 received placebo daily. The primary endpoint was time to disease progression (TTP) defined as the onset of metastases. Secondary endpoints were time to PSA progression, change in bone alkaline phosphatase (BALP), PSA doubling time, and overall survival.
Atrasentan delayed median TTP by 93 days but the difference from placebo was not statistically significant (P = .288). Large geographical differences in median TTP were noted: in the United States (US), the difference was 81 days longer with placebo, whereas in non-US sites, the difference was 180 days longer with atrasentan. Atrasentan lengthened PSA doubling time (P = .031) and slowed the increase in BALP (P < .001). Median survival was 1477 days with atrasentan and 1403 days with placebo. The most common adverse events associated with atrasentan were peripheral edema, nasal congestion, and headache, consistent with the vasodilatory properties of ETA receptor antagonists.
While the primary endpoint was not achieved, large regional differences in TTP were noted, suggesting that trial conduct might have influenced the results. The biological activity is consistent with findings from other clinical trials of atrasentan in HRPC.
Skeletal complications are a major cause of morbidity in men with hormone-refractory metastatic prostate cancer. These analyses were designed to identify the variables associated with a greater risk of skeletal complications.
The 643 subjects in this report were participants in a randomized placebo-controlled trial to evaluate the effects of zoledronic acid on the incidence of skeletal-related events. All subjects had bone metastases and disease progression despite medical or surgical castration. The relationships between the baseline covariates and the time to the first skeletal-related event were assessed by Cox proportional hazard analyses. The serum bone-specific alkaline phosphatase (BAP) and urinary N-telopeptide level was assessed as a representative specific marker of osteoblastic and osteoclastic activity, respectively. The other covariates included in the model were age, cancer duration, Eastern Cooperative Oncology Group performance status, analgesic use, and prostate-specific antigen, hemoglobin, and lactate dehydrogenase levels.
Elevated BAP levels were consistently associated with a greater risk of adverse skeletal outcomes. Elevated BAP was significantly associated with a shorter time to the first skeletal-related event on multivariate analyses of the entire study population (relative risk 1.84, 95% confidence interval 1.40 to 2.43; P <0.001) and in subset analyses of the placebo and zoledronic acid groups. Elevated BAP levels were also consistently associated with adverse skeletal outcomes on multivariate analyses of the time to radiotherapy and pathologic fracture, the most common types of skeletal-related events in the study population. No other baseline variable was consistently associated with the risk of adverse skeletal outcomes.
The results of our study have shown that elevated serum BAP levels are associated with a greater risk of adverse skeletal outcomes in men with hormone-refractory prostate cancer and bone metastases.