Posttreatment prostatic-specific antigen doubling time as a surrogate endpoint for prostate cancer-specific survival: An analysis of Radiation Therapy Oncology Group Protocol 92–02

Biochemical Failure Is Not a Surrogate End Point for Overall Survival in Recurrent Prostate Cancer: Analysis of NRG Oncology/RTOG 9601

PURPOSE

Metastasis-free survival (MFS), but not event-free survival, is a validated surrogate end point for overall survival (OS) in men treated for localized prostate cancer. It remains unknown if this holds true in biochemically recurrent disease after radical prostatectomy. Leveraging NRG/RTOG 9601, we aimed to determine the performance of intermediate clinical end points (ICEs) as surrogate end points for OS in recurrent prostate cancer.

MATERIALS AND METHODS

NRG/RTOG 9601 randomly assigned 760 men with recurrence after prostatectomy to salvage radiation therapy with 2 years of placebo versus bicalutamide 150 mg daily. ICEs assessed were biochemical failure (BF) per NRG/RTOG 9601 (prostate-specific antigen nadir + 0.3-0.5 ng/mL or initiation of salvage hormone therapy; [BF1]) and NRG/RTOG 0534 (prostate-specific antigen nadir+2 ng/mL; [BF2]), distant metastasis (DM), and MFS (DM or death). Surrogacy was assessed by the Prentice criteria and a two-stage meta-analytic approach (condition one assessed at the patient level with Kendall's τ and condition two assessed by randomly dividing the entire trial cohort into 10 pseudo trial centers and calculating the average R2 between treatment hazard ratios for ICE and OS).

RESULTS

BF1, BF2, DM, and MFS satisfied the four Prentice criteria. However, with the two-condition meta-analytic approach, there was strong correlation between MFS and OS (τ = 0.86), moderate correlation between DM and OS (τ = 0.66), and weaker correlation between BF1 (τ = 0.25) or BF2 (τ = 0.40) and OS. Similarly, for condition two, the treatment effect of antiandrogen therapy on MFS and OS were correlated (R2 = 0.67), but this was not true for BF1 (R2 = 0.09), BF2 (R2 = 0.12), or DM (R2 = 0.18) and OS.

CONCLUSION

MFS is also a strong surrogate for OS in men receiving salvage radiation therapy for recurrence after prostatectomy. Caution should be used when inferring survival benefit from effects on BF in biochemically recurrent prostate cancer. Lack of comorbidity data did not allow us to assess whether BF in men with no/minimal comorbidity could serve as a surrogate for OS.

Surrogate Endpoints in Localized Prostate Cancer

Randomized clinical trials assessing novel therapies in men with localized prostate cancer frequently require large patient numbers and more than a decade of follow-up to demonstrate improvements in overall survival. As the landscape of treatment options for prostate cancer is rapidly changing, clinical trials requiring long follow-up threaten to impede treatment improvements and run the risk of results being obsolete by the time that they are reported in publication. To address these issues, there has been tremendous interest in identifying an intermediate clinical endpoint that can be assessed earlier in the disease course to serve as a robust surrogate for overall survival in men with localized prostate cancer. Herein we review the relevant data for surrogate endpoints in localized prostate cancer, highlighting the work performed by the Intermediate Clinical Endpoints in Cancer of the Prostate Working Group identifying metastasis-free survival as a valid surrogate for men treated for localized prostate cancer.

Radiation dose-response (a Bayesian model) in the radiotherapy of the localized prostatic adenocarcinoma: the reliability of PSA slope changes as a response surrogate endpoint

Purpose

One of the characteristics of Prostate-Specific Antigen (PSA) is PSA slope. It is the rate of diminishing PSA marker over time after radiotherapy (RT) in prostate cancer (PC) patients. The purpose of this study was to evaluate the relationship between increasing RT doses and PSA slope as a potential surrogate for PC recurrence.

Patients and Methods

This retrospective study was conducted on PC patients who were treated by radiotherapy in the Cancer Institute of Iran during 2007–2012. By reviewing the records of these patients, the baseline PSA measurement before treatment (iPSA), Gleason score (GS), clinical T stage (T. stage), and periodic PSA measurements after RT and the total radiation dose received were extracted for each patient separately. We used a Bayesian dose-response model, analysis of variance, Kruskal–Wallis test, Kaplan–Meier product-limit method for analysis. Probability values less 0.05 were considered statistically significant.

Results

Based on the D’Amico risk assessment system, 13.34% of patients were classified as “Low Risk”, 51.79% were “Intermediate Risk”, and 34.87% were “High Risk”. In terms of radiation doses, 12.31% of the patients received fewer than 50 Gy, 15.38% received 50 to 69 Gy, 61.03% received 70 Gy, and 11.28% received more than 70 Gy. The PSA values decreased after RT for all dose levels. The slope of PSA changes was negative for 176 of 195 patients. By increasing the dosage of radiation, the PSA decreased but these changes were not statistically significant (p = 0.701) and PSA slope as a surrogate end point cannot met the Prentice’s criteria for PC recurrence.

Conclusion

Significant changes in the dose-response relationship were not observed when the PSA slope was considered as the response criterion. Therefore, although the absolute value of the PSA decreased with increasing doses of RT, the relationship between PSA slope changes and increasing doses was not clear and cannot be used as a reliable response surrogate endpoint.

Time Interval to Biochemical Failure as a Surrogate End Point in Locally Advanced Prostate Cancer: Analysis of Randomized Trial NRG/RTOG 9202

BACKGROUND

In prostate cancer, end points that reliably portend prognosis and treatment benefit (surrogate end points) can accelerate therapy development. Although surrogate end point candidates have been evaluated in the context of radiotherapy and short-term androgen deprivation (AD), potential surrogates under long-term (24 month) AD, a proven therapy in high-risk localized disease, have not been investigated.

MATERIALS AND METHODS

In the NRG/RTOG 9202 randomized trial (N = 1,520) of short-term AD (4 months) versus long-term AD (LTAD; 28 months), the time interval free of biochemical failure (IBF) was evaluated in relation to clinical end points of prostate cancer-specific survival (PCSS) and overall survival (OS). Survival modeling and landmark analysis methods were applied to evaluate LTAD benefit on IBF and clinical end points, association between IBF and clinical end points, and the mediating effect of IBF on LTAD clinical end point benefits.

RESULTS

LTAD was superior to short-term AD for both biochemical failure (BF) and the clinical end points. Men remaining free of BF for 3 years had relative risk reductions of 39% for OS and 73% for PCSS. Accounting for 3-year IBF status reduced the LTAD OS benefit from 12% (hazard ratio [HR], 0.88; 95% CI, 0.79 to 0.98) to 6% (HR, 0.94; 95% CI, 0.83 to 1.07). For PCSS, the LTAD benefit was reduced from 30% (HR, 0.70; 95% CI, 0.52 to 0.82) to 6% (HR, 0.94; 95% CI, 0.72 to 1.22). Among men with BF, by 3 years, 50% of subsequent deaths were attributed to prostate cancer, compared with 19% among men free of BF through 3 years.

CONCLUSION

The IBF satisfied surrogacy criteria and identified the benefit of LTAD on disease-specific survival and OS. The IBF may serve as a valid end point in clinical trials and may also aid in risk monitoring after initial treatment.

Surrogate endpoints in early prostate cancer research

Clinical research into clinically-localized prostate cancer (PC) is a highly challenging environment. The protracted durations and large numbers required to achieve survival endpoints have placed much pressure on validating early surrogate endpoints. Further confounding is the predominance of deaths from causes other than PC. The analysis of multiple randomized clinical trials in early PC has shown MFS to be a robust surrogate for OS, using a contemporary analytic framework that identify patient-level and trial-level associations. This could potentially save around one year of trial follow-up in some therapies. Identification of a similarly robust surrogate at a substantially earlier timepoint remains a major challenge. Multiple biochemical indices based on PSA have been proposed in the literature, but all remain to be validated at the trial-level. Operationally, many of these indices have inherent biases such as immortal-time bias (ITB) and interval censoring that potentially weakens associations and the individual- or trial-level. The complexity of a failure definition can also impact the reliability of the derived outcomes. Confounding issues such as the impact of comorbidities leading to non-cancer deaths have been largely dealt with by their exclusion using cancer-specific endpoints and advanced statistical methods, while issues such as PSA "bounce" and recovery from androgen deprivation therapy remain important to account for in cohorts treated with radiotherapy. Several potential surrogate endpoints based on serum prostate-specific antigen (PSA) levels show promising associations with PC-specific and overall survival (OS) in individual studies. Further large collaborative projects will continue to refine potential indices with these issues in mind, and explore the objective of an early surrogate of OS.

A two-stage model in a Bayesian framework to estimate a survival endpoint in the presence of confounding by indication

Background

Biomarker series can indicate disease progression and predict clinical endpoints. When a treatment is prescribed depending on the biomarker, confounding by indication might be introduced if the treatment modifies the marker profile and risk of failure.

Objective

Our aim was to highlight the flexibility of a two-stage model fitted within a Bayesian Markov Chain Monte Carlo framework. For this purpose, we monitored the prostate-specific antigens in prostate cancer patients treated with external beam radiation therapy. In the presence of rising prostate-specific antigens after external beam radiation therapy, salvage hormone therapy can be prescribed to reduce both the prostate-specific antigens concentration and the risk of clinical failure, an illustration of confounding by indication. We focused on the assessment of the prognostic value of hormone therapy and prostate-specific antigens trajectory on the risk of failure.

Methods

We used a two-stage model within a Bayesian framework to assess the role of the prostate-specific antigens profile on clinical failure while accounting for a secondary treatment prescribed by indication. We modeled prostate-specific antigens using a hierarchical piecewise linear trajectory with a random changepoint. Residual prostate-specific antigens variability was expressed as a function of prostate-specific antigens concentration. Covariates in the survival model included hormone therapy, baseline characteristics, and individual predictions of the prostate-specific antigens nadir and timing and prostate-specific antigens slopes before and after the nadir as provided by the longitudinal process.

Results

We showed positive associations between an increased prostate-specific antigens nadir, an earlier changepoint and a steeper post-nadir slope with an increased risk of failure. Importantly, we highlighted a significant benefit of hormone therapy, an effect that was not observed when the prostate-specific antigens trajectory was not accounted for in the survival model.

Conclusion

Our modeling strategy was particularly flexible and accounted for multiple complex features of longitudinal and survival data, including the presence of a random changepoint and a time-dependent covariate.

The Development of Intermediate Clinical Endpoints in Cancer of the Prostate (ICECaP)

New systemic therapies have prolonged the lives of men with metastatic castration-resistant prostate cancer (mCRPC). Use of these therapies in the adjuvant setting when the disease may be micrometastatic and potentially more sensitive to therapies may decrease mortality from prostate cancer. However, the conduct of adjuvant prostate cancer clinical trials is hampered by taking longer than a decade to reach the meaningful endpoint of overall survival (OS) and the fact that many men never die from prostate cancer, even if they relapse. A validated intermediate clinical endpoint (ICE) in prostate cancer that is a robust surrogate for OS has yet to be defined. This paper details the plans, process, and progress of the international Intermediate Clinical Endpoints in Cancer of the Prostate (ICECaP) working group to pool individual patient data from all available clinical trials of radiation or prostatectomy for localized disease and conduct the requisite analyses to determine whether an ICE can be identified. This paper further details the challenges and the a priori statistical analytical plans and strategies to define an ICE for adjuvant prostate cancer clinical trials. In addition, a brief review of the health economic analyses to model the benefits to patients, society and manufacturers is detailed. If successful, the results from this work will provide a robust surrogate for OS that will expedite the design and conduct of future adjuvant therapy trials using new agents that have proven activity in mCRPC. Moreover, it will also define the health economic benefits to patients and societies.

A Phase II trial of a combination herbal supplement for men with biochemically recurrent prostate cancer

BACKGROUND

Men with biochemical recurrence (BCR) of prostate cancer are typically observed or treated with androgen-deprivation therapy. Non-hormonal, non-toxic treatments to slow the rise of PSA are desirable. We studied a combination herbal supplement, Prostate Health Cocktail (PHC), in prostate cancer cell lines and in a population of men with BCR.

METHODS

PC3, LAPC3 and LNCaP cells were incubated with increasing concentrations of PHC suspension. Men previously treated for prostate cancer with surgery, radiation or both with rising PSA but no radiographic metastases were treated with three capsules of PHC daily; the primary end point was 50% PSA decline. Circulating tumor cells (CTCs) were identified using parylene membrane filters.

RESULTS

PHC showed a strong dose-dependent anti-proliferative effect in androgen-sensitive and independent cell lines in vitro and suppression of androgen receptor expression. Forty eligible patients were enrolled in the clinical trial. Median baseline PSA was 2.8 ng ml(-1) (1.1-84.1) and 15 men (38%) had a PSA decline on study (1-55% reduction); 25 (62%) had rising PSA on study. The median duration of PSA stability was 6.4 months. Two patients had grade 2/3 transaminitis; the only other grade 2 toxicities were hyperglycemia, hypercalcemia and flatulence. There were no significant changes in testosterone or dihydrotestosterone. CTCs were identified in 19 men (47%).

CONCLUSIONS

Although the primary end point was not met, PHC was well tolerated and was associated with PSA declines and stabilization in a significant number of patients. We believe this is the first report of detecting CTCs in men with BCR prostate cancer. Randomized studies are needed to better define the effect of PHC in men with BCR.

Impact of biochemical failure classification on clinical outcome: a secondary analysis of Radiation Therapy Oncology Group 9202 and 9413

BACKGROUND

Biochemical failure (BF) after radiation therapy is defined on the basis of a rising prostate-specific antigen (PSA) level (A1 failure) or any event that prompts the initiation of salvage androgen-deprivation therapy without PSA failure (A2). It was hypothesized that A2 failure may have a different prognosis.

METHODS

Data for 2799 eligible patients from Radiation Therapy Oncology Group (RTOG) 9202 and RTOG 9413 were analyzed. BF was defined according to the 1997 American Society for Therapeutic Radiology and Oncology consensus definition as A1 for PSA failure or as A2 for the start of salvage hormone therapy before 3 consecutive PSA rises.

RESULTS

Rates of all-cause mortality (hazard ratio [HR], 1.7; 95% confidence interval [CI], 1.5-2.0; P < .0001) and distant metastasis (DM; HR, 1.6; 95% CI, 1.3-2.0; P < .0001) were greater with A2 failure. The 5-year overall survival (OS) rates were 88.2% and 74.6% for A1 and A2, respectively (P < .0001), and the DM rates were 15.7% and 29.0%, respectively (P < .0001). The DM rate was greater at 5 years for A2 patients with DM as the first sign of failure versus patients with other A2 failures (87.3% vs 11.7%, P < .001), and this also correlated with worse OS at 5 years: 81.1% for A2 failure without DM and 52.8% with DM (P < .001). After the removal of patients with DM, the difference between A1 and A2 BF persisted for OS (P = .002) but not for DM (P = .16) CONCLUSIONS: These results suggest that patients with rising PSA levels alone have less risk than those with A2 failures; although DM was the largest contributor of adverse risk to A2 failure, it did not account for all excess risk in A2 failure.

The dilemma of a rising prostate-specific antigen level after local therapy: what are our options?

Prostate cancer is the most common solid tumor diagnosed in men in the United States and Western Europe. Primary treatment with radiation or surgery is largely successful at controlling localized disease. However, a significant number (up to one third of men) may develop biochemical recurrence (BR), defined as a rise in serum prostate-specific antigen (PSA) level. A general presumption is that BR will lead to overt progression in patients over subsequent years. There are a number of factors that a physician must consider when counseling and recommending treatment to a patient with a rising PSA. These include the following (1) various PSA-based definitions of BR; (2) source of PSA (ie, local or distant disease, residual benign prostate); (3) available modalities to treat the disease with the least morbidity; and (4) timing of therapy. In this article we review the current and future factors that clinicians should consider in the diagnosis and treatment of recurrent prostate cancer.

Diabetes mellitus is associated with short prostate-specific antigen doubling time after radical prostatectomy

OBJECTIVE

To investigate whether diabetes mellitus (DM) was associated with postoperative outcomes, including prostate-specific antigen doubling time, among men who underwent radical prostatectomy (RP) for clinically localized prostate cancer (PCa).

METHODS

Data of 661 patients who underwent radical prostatectomy for node-negative prostate cancer and were followed up for ≥3 years postoperatively at our institution were analyzed. Associations between diabetes mellitus at surgery and outcomes following radical prostatectomy, such as biochemical recurrence-free survival and prostate-specific antigen doubling time, were examined. Aggressive recurrence was defined as biochemical recurrence with prostate-specific antigen doubling time <9 months.

RESULTS

Of the 661 total subjects, DM (n = 67, 10.1 %) and non-DM group (n = 594, 89.9 %) showed no significant differences in various clinicopathologic parameters including age and PSA. DM group had lower postoperative biochemical recurrence-free survival than non-DM group, with observed difference approaching statistical significance (log-rank, p = 0.077). On multivariate analysis, DM at surgery was significantly associated with aggressive recurrence following RP (p = 0.048). Pathologic Gleason score (p = 0.008) and seminal vesicle invasion (p = 0.010) were also significantly associated with aggressive recurrence on multivariate analysis.

CONCLUSION

Our results show that pre-existing DM in men with PCa is associated with more aggressive recurrence, suggesting that DM may affect disease progression following RP. Further investigation would be needed to elucidate exact biologic interaction between DM and PCa and also assess causal relationships that potentially could be modified to improve long-term outcome in patients with the two diseases.

Validating the interval to biochemical failure for the identification of potentially lethal prostate cancer

PURPOSE

To validate the interval to biochemical failure (IBF) as a prognostic factor at the time of biochemical failure for prostate cancer mortality (PCM) following radiotherapy (RT).

PATIENTS AND METHODS

From a collaborative data set of men with clinically localized prostate cancer treated with RT from four institutions in three countries, we identified 1,722 men with biochemical failure (BF; prostate-specific antigen nadir + 2 ng/mL). The IBF was defined as the time interval from completion of treatment to the date of BF. The primary outcome measure was discriminatory power in the form of the concordance index (c-index).

RESULTS

Seventeen percent of men had an IBF ≤ 18 months. Median potential follow-up beyond the time of BF was 67 months. There were 290 deaths from prostate cancer. The IBF was the most discriminating individual prognostic factor overall, with a sensitivity of IBF ≤ 18 months to predict PCM within 10 years of 48.4% (95% CI, 43.3% to 54.1%); the specificity was 86.1% (95% CI, 84.5% to 87.7%), equating to a c-index of 0.611 (95% CI, 0.578 to 0.647). The 5-year cumulative incidence of PCM for IBF more than 18 months versus IBF ≤ 18 months was 9.4% (95% CI, 7.7% to 11.5%) versus 26.3% (95% CI, 21.2% to 31.8%); corresponding 10-year estimates were 26.2% (95% CI, 21.5% to 30.8%) versus 55.9% (95% CI, 48.9% to 63.0%), respectively (P < .001 for both). IBF exhibited minimal change in performance across various follow-up durations.

CONCLUSION

IBF is the single most robust prognostic factor for PCM following RT without androgen deprivation therapy. This external validation demonstrates that patients and clinicians can use this information to make decisions about subsequent treatments.

Feasibility of adenovirus-mediated hNIS gene transfer and 131I radioiodine therapy as a definitive treatment for localized prostate cancer

We have developed a replication-competent adenovirus (Ad5-yCD/mutTK(SR39)rep-hNIS) armed with two suicide genes and the human sodium iodide symporter (hNIS) gene. In this context, hNIS can be used as a reporter gene in conjunction with nuclear imaging and as a potentially therapeutic gene when combined with (131)I radioiodine therapy. Here, we quantified the volume and magnitude of hNIS gene expression in the human prostate following injection of a high Ad5-yCD/mutTK(SR39)rep-hNIS dose using a standardized injection algorithm, and estimated the radiation dose that would be delivered to the prostate had men been administered (131)I with curative intent. Six men with clinically localized prostate cancer received an intraprostatic injection of Ad5-yCD/mutTK(SR39)rep-hNIS under transrectal ultrasound guidance. All men received 2 × 0.5 ml deposits (5 × 10(11) vp/deposit) in each of the four base and midgland sextants and 2 × 0.25 ml deposits (2.5 × 10(11) vp/deposit) in each of the two apex sextants for a total of 12 deposits (5 × 10(12) vp) in 5 ml. On multiple days after the adenovirus injection, men were administered sodium pertechnetate (Na(99m)TcO(4)) and hNIS gene expression in the prostate was quantified by single photon emission computed tomography (SPECT). hNIS gene expression was detected in the prostate of six of six (100%) men. On average, 45% (range 18-83%) of the prostate volume was covered with gene expression. Had men been administered 200 mCi (131)I, we estimate that the mean absorbed dose to the prostate would be 7.2 ± 4.8 Gy (range 2.1-13.3 Gy), well below that needed to sterilize the prostate. We discuss the obstacles that must be overcome before adenovirus-mediated hNIS gene transfer and (131)I radioiodine therapy can be used as a definitive treatment for localized prostate cancer.

Randomized trial of autologous cellular immunotherapy with sipuleucel-T in androgen-dependent prostate cancer

PURPOSE

Sipuleucel-T, an autologous cellular immunotherapy, was investigated in a randomized, double-blind, controlled trial to determine its biologic activity in androgen-dependent prostate cancer (ADPC).

EXPERIMENTAL DESIGN

Patients with prostate cancer detectable by serum prostate-specific antigen (PSA) following radical prostatectomy received 3 to 4 months of androgen suppression therapy, and were then randomized (2:1) to receive sipuleucel-T (n = 117) or control (n = 59). The primary endpoint was time to biochemical failure (BF) defined as serum PSA ≥ 3.0 ng/mL. PSA doubling time (PSADT), time to distant failure, immune response, and safety were also evaluated.

RESULTS

Median time to BF was 18.0 months for sipuleucel-T and 15.4 months for control (HR = 0.936, P = 0.737). Sipuleucel-T patients had a 48% increase in PSADT following testosterone recovery (155 vs. 105 days, P = 0.038). With only 16% of patients having developed distant failure, the treatment effect favored sipuleucel-T (HR = 0.728, P = 0.421). The most frequent adverse events in sipuleucel-T patients were fatigue, chills, and pyrexia. Immune responses to the immunizing antigen were greater in sipuleucel-T patients at Weeks 4 and 13 (P < 0.001, all) and were sustained prior to boosting as measured in a subset of patients a median of 22.6 months (range: 14.3-67.3 months) following randomization.

CONCLUSIONS

No significant difference in time to BF could be shown. The finding of increased PSADT in the sipuleucel-T arm is consistent with its biologic activity in ADPC. Long-term follow-up will be necessary to determine if clinically important events, such as distant failure, are affected by therapy. Treatment was generally well tolerated.

Adaptive seamless design for an efficacy trial of replication-competent adenovirus-mediated suicide gene therapy and radiation in newly-diagnosed prostate cancer (ReCAP Trial)

PURPOSE

Cumulative evidence has suggested investigation of the efficacy of Replication-Competent Adenovirus-mediated Suicide Gene Therapy in newly-diagnosed Prostate Cancer (ReCAP). There is a challenge in designing an efficacy trial for newly-diagnosed prostate cancer given its long natural history. The regulatory agency recommended a Phase II trial for safety before conducting the efficacy trial.

EXPERIMENTAL DESIGN

The ReCAP trial is an adaptive seamless, multi-site open-label, randomized Phase II/III trial. Two hundred eighty men will be randomized to receive either replication-competent adenovirus-mediated suicide gene therapy followed by radiation (Arm 1) or radiation alone (Arm 2). Phase II trial component will include the first 21 patients in Arm 1 with complete toxicity through day 90 for safety evaluation. The primary efficacy endpoint is the time free from biochemical and/or clinical failure (FFF). The secondary efficacy endpoints are 2-year prostate biopsies and overall survival. Unequal spaced interim looks are proposed with the adaptive sample-size re-estimation.

RESULTS

This trial has been approved by the FDA for the study therapy investigation and is currently recruiting patients.

CONCLUSIONS

Challenges remain in designing newly-diagnosed prostate cancer trials. Adaptive seamless design is time-saving and a cost-effective design in the development of novel medical therapies, but requires a specified statistical plan in the decision process involved.

Does PSADT after radical prostatectomy correlate with overall survival?--a report from the SEARCH database group

OBJECTIVES

To examine the correlation between the prostate-specific antigen doubling time (PSADT) and overall survival (OS) and among men in the SEARCH database (an older, racially diverse cohort undergoing RP at multiple Veterans Affairs medical centers). Previous studies largely performed at tertiary care centers with relatively young, racially homogenous cohorts found a short PSADT on recurrence after RP portended a poor prognosis.

METHODS

We performed a Cox proportional hazards analysis to examine the correlation between postrecurrence PSADT and the interval from recurrence to OS and prostate cancer-specific mortality among 345 men in the SEARCH database who had undergone RP from 1988 to 2008. We examined the PSADT as a categorical variable using the clinically significant cutpoints of <3, 3-8.9, 9-14.9, and ≥15 months.

RESULTS

A PSADT of <3 months (hazard ratio 5.48, P = .002) was associated with poorer OS than a PSADT of ≥15 months. A trend was seen toward worse OS for the men with a PSADT of 3-8.9 months (hazard ratio 1.70, P = .07). PSADTs of <3 months (P < .001) and 3-8.9 months (P = .004) were associated with an increased risk of prostate cancer-specific mortality.

CONCLUSIONS

In an older, racially diverse cohort, recurrence with a PSADT of <9 months was associated with worse all-cause mortality. The results of the present study have validated previous findings that PSADT is a useful tool for identifying men at increased risk of all-cause mortality early in their disease course.

Predicting biopsy-proven prostate cancer recurrence following cryosurgery

OBJECTIVES

Prostate cancer (CaP) cryosurgery utilizes PSA nadir level and radiotherapy criteria as surrogates for success. We attempted to correlate PSA doubling time (PSAdt) and time of undetectable PSA (TUPSA) with biopsy-proven cancer recurrence (BPR) in men treated with primary third-generation cryotherapy for clinically localized CaP.

MATERIALS AND METHODS

Demographic, clinical, and pathologic data was retrieved including age, race, use of preoperative hormones or 5-α reductase inhibitors (5-ARIs), initial biopsy PSA, biopsy Gleason score, cT stage, prostate volume, presence/absence median lobe, and follow-up. Post-cryotherapy biopsy was considered for PSA levels ≥ 0.5 ng/ml. PSAdt was determined by the log-slope method. TUPSA was defined as time from surgery to a PSA value ≥ 0.2 ng/ml or most recent follow-up if undetectable.

RESULTS

Ninety-seven patients were identified. Preoperative hormonal manipulation was used in 25 (26%); 5 (5%) were using a 5-ARI. Twenty-seven (29%) underwent post-cryotherapy biopsy, 12 (12%) had a BPR. In 41 (42%), PSAdt was calculated (median 11.9 months, IQR 6.6-34.8); no significant difference between patients with BPR and without CaP was found (P = 0.46). TUPSA was a median of 4.9 months (IQR 3.2-9.9) vs. 15.6 months (IQR 6.1-30.3) for BPR or no CaP, respectively (P = 0.005). On proportional hazards regression, TUPSA was the only independent predictor of BPR (P = 0.03, OR 0.91).

CONCLUSIONS

Post-cryosurgery PSAdt does not appear to be associated with BPR risk, whereas TUPSA reduces the risk of BPR by 9% per month. This may help guide management if local failure is suspected.

External validation of the SEARCH model for predicting aggressive recurrence after radical prostatectomy: results from the Duke Prostate Center Database

OBJECTIVE

To validate a model previously developed using the Shared Equal Access Regional Cancer Hospital (SEARCH) database to predict the risk of aggressive recurrence after surgery, defined as a prostate-specific antigen (PSA) doubling time (DT) of <9 months, incorporating pathological stage, preoperative PSA level and pathological Gleason sum, that had an area under the curve (AUC) of 0.79 using a cohort of men from the Duke Prostate Center (DPC).

PATIENTS AND METHODS

Data were included from 1989 men from the DPC database who underwent RP for node-negative prostate cancer between 1987 and 2003. Of these men, 100 had disease recurrence, with a PSADT of <9 months, while 1889 either did not have a recurrence but had > or =36 months of follow-up or had a recurrence with a PSADT of > or =9 months. We examined the ability of the SEARCH model to predict aggressive recurrence within the DPC cohort, and examined the correlation between the predicted risk of aggressive recurrence and the actual outcome within DPC.

RESULTS

The SEARCH model predicted aggressive recurrence within DPC with an AUC of 0.82. There was a strong and significant correlation between the predicted risk of aggressive recurrence based on the SEARCH tables and the actual outcomes within DPC (r= 0.68, P < 0.001), although the model predictions tended to be slightly higher than the actual risk.

CONCLUSIONS

The SEARCH model to predict aggressive recurrence after RP predicted aggressive recurrence in an external dataset with a high degree of accuracy. These tables, now validated, can be used to help select men for adjuvant therapy and clinical trials.

Freedom from a detectable ultrasensitive prostate-specific antigen at two years after radical prostatectomy predicts a favorable clinical outcome: analysis of the SEARCH database

OBJECTIVES

To assess the utility of kinetics for ultrasensitive prostate-specific antigen (uPSA) assays to identify men who are at risk of developing high-risk recurrent prostate cancer [prostate-specific antigen doubling time (PSADT) < 9 months] after radical prostatectomy. Previous studies demonstrate that a PSADT < 9 months after radical prostatectomy is associated with prostate cancer-specific mortality. Conventionally, PSADT has been calculated after biochemical failure (PSA > or = 2 0.2 ng/mL).

METHODS

A review of the Shared Equal Access Regional Cancer Hospital database from 1988-2008 was performed to identify men with biochemical failure after radical prostatectomy and > or = 2 uPSA values before failure (PSA > or = 2 0.2 ng/mL) as well as > or = 2 2 values after failure to calculate PSADT. These patients were stratified into low-risk (PSADT > or = 2 9 months) and high-risk (PSADT < 9 months) cohorts. The following uPSA kinetics were analyzed for their ability to predict low- and high-risk cohorts: time to first detectable uPSA, time from uPSA to biochemical failure, uPSA velocity, uPSADT, uPSA exponential rise, and uPSA fluctuations.

RESULTS

The analysis included 89 low- and 26 high-risk men. Time to first detectable uPSA was inversely associated with the high-risk cohort (OR 0.96, 95% CI 0.92-0.99, P = .02) and characterized by a high sensitivity and negative predictive value at a threshold of 2 years after surgery. Other measures of uPSA kinetics showed no association with PSADT.

CONCLUSIONS

Time to first detectable uPSA identifies men with low-risk recurrence prostate cancer. Patients with an undetectable uPSA 2 years after surgery are unlikely to develop PSADT < 9 months after biochemical failure.

Transcriptionally regulated, prostate-targeted gene therapy for prostate cancer

Prostate cancer is the most frequently diagnosed cancer and the second leading cause of cancer deaths in American males today. Novel and effective treatment such as gene therapy is greatly desired. The early viral based gene therapy uses tissue-nonspecific promoters, which causes unintended toxicity to other normal tissues. In this chapter, we will review the transcriptionally regulated gene therapy strategy for prostate cancer treatment. We will describe the development of transcriptionally regulated prostate cancer gene therapy in the following areas: (1) Comparison of different routes for best viral delivery to the prostate; (2) Study of transcriptionally regulated, prostate-targeted viral vectors: specificity and activity of the transgene under several different prostate-specific promoters were compared in vitro and in vivo; (3) Selection of therapeutic transgenes and strategies for prostate cancer gene therapy (4) Oncolytic virotherapy for prostate cancer. In addition, the current challenges and future directions in this field are also discussed.

Potential surrogate endpoints for prostate cancer survival: analysis of a phase III randomized trial

BACKGROUND

The identification of surrogate endpoints for prostate cancer-specific survival may shorten the length of clinical trials for prostate cancer. We evaluated distant metastasis and general clinical treatment failure as potential surrogates for prostate cancer-specific survival by use of data from the Radiation Therapy and Oncology Group 92-02 randomized trial.

METHODS

Patients (n = 1554 randomly assigned and 1521 evaluable for this analysis) with locally advanced prostate cancer had been treated with 4 months of neoadjuvant and concurrent androgen deprivation therapy with external beam radiation therapy and then randomly assigned to no additional therapy (control arm) or 24 additional months of androgen deprivation therapy (experimental arm). Data from landmark analyses at 3 and 5 years for general clinical treatment failure (defined as documented local disease progression, regional or distant metastasis, initiation of androgen deprivation therapy, or a prostate-specific antigen level of 25 ng/mL or higher after radiation therapy) and/or distant metastasis were tested as surrogate endpoints for prostate cancer-specific survival at 10 years by use of Prentice's four criteria. All statistical tests were two-sided.

RESULTS

At 3 years, 1364 patients were alive and contributed data for analysis. Both distant metastasis and general clinical treatment failure at 3 years were consistent with all four of Prentice's criteria for being surrogate endpoints for prostate cancer-specific survival at 10 years. At 5 years, 1178 patients were alive and contributed data for analysis. Although prostate cancer-specific survival was not statistically significantly different between treatment arms at 5 years (P = .08), both endpoints were consistent with Prentice's remaining criteria.

CONCLUSIONS

Distant metastasis and general clinical treatment failure at 3 years may be candidate surrogate endpoints for prostate cancer-specific survival at 10 years. These endpoints, however, must be validated in other datasets.

What are the factors associated with short prostate specific antigen doubling time after radical prostatectomy? A report from the SEARCH database group

PURPOSE

Short prostate specific antigen doubling time following recurrence after radical prostatectomy portends a poor prognosis in men with prostate cancer. We determined which demographic and clinicopathological variables were predictive of a short prostate specific antigen doubling time in a cohort of men with clinically localized prostate cancer treated with radical prostatectomy.

MATERIALS AND METHODS

Data on 856 men from the Shared Equal Access Regional Cancer Hospital database who underwent radical prostatectomy for node negative prostate cancer between 1988 and 2003 were included in the analysis. We used logistic regression analysis to determine the independent factors associated with a short prostate specific antigen doubling time of less than 9 months vs a longer doubling time of 9 months or greater, or no recurrence. The variables analyzed were patient age, race, logarithmically transformed preoperative prostate specific antigen, body mass index, year of surgery, pathological Gleason sum, extraprostatic extension, surgical margin status and seminal vesicle invasion.

RESULTS

On multivariate analysis higher preoperative prostate specific antigen (OR 2.20, 95% CI 1.52-3.19, p <0.001), pathological Gleason sum 8-10 (OR 4.70, 95% CI 2.11-10.43, p <0.001) and 7 (OR 2.11, 95% CI 1.09-4.08, p = 0.026), tumors with extraprostatic extension and/or positive surgical margins (OR 2.08, 95% CI 1.48-3.91, p = 0.023), and seminal vesicle invasion (OR 3.26, 95% CI 1.48-7.21, p = 0.003) were independent predictors of a short prostate specific antigen doubling time. Based on these risk factors we developed a table to estimate the risk of recurrence with a prostate specific antigen doubling time of less than 9 months.

CONCLUSIONS

The factors that are invariably used to predict overall biochemical recurrence following radical prostatectomy, including high prostate specific antigen, high grade and adverse pathological findings, also predict aggressive recurrence.

Risk of prostate cancer recurrence in men treated with radiation alone or in conjunction with combined or less than combined androgen suppression therapy

PURPOSE

We determined the risk of recurrence in men enrolled on a randomized trial for prostate cancer who were treated with radiation therapy (RT) alone or in conjunction with combined or less than combined androgen suppression therapy (AST).

PATIENTS AND METHODS

Between 1995 and 2001, 206 men with localized but unfavorable-risk adenocarcinoma of the prostate were randomly assigned to receive RT or RT and AST, which was defined as 6 months of both a luteinizing hormone-releasing hormone agonist and an antiandrogen. A post-random assignment hypothesis that was generated by multivariable Cox regression analyses was used to evaluate whether the risk of prostate-specific antigen (PSA) recurrence was significantly associated with months of antiandrogen use; regression analysis adjusted for known prognostic factors, comorbidity score, and medications that can elevate liver function tests sufficiently to necessitate discontinuation of the antiandrogen.

RESULTS

After a median follow-up of 8.2 years (interquartile range,7.0 to 9.5 years), 81 men sustained PSA recurrence. An increasing PSA level (P < .001); Gleason score of 8, 9, or 10 (P < .001); and clinical category T2 disease (P = .005) were significantly associated with an increased risk of recurrence. However, recurrence risk was significantly decreased (adjusted hazard ratio, 0.81; 95% CI, 0.72 to 0.92; P = .001) with each additional month of antiandrogen use after analysis was adjusted for these known prognostic factors.

CONCLUSION

Men with localized but unfavorable-risk prostate cancer who were treated with RT and 6 months of planned combined AST appear to have an increased risk of recurrence when treated with less than as compared with 6 months of the antiandrogen.

Predicting biochemical failure and overall survival through intratherapy PSA changes during definitive external beam radiotherapy

PURPOSE

To determine whether intratherapy prostate-specific antigen (itPSA) changes during radiotherapy (RT) predict prostate cancer outcomes.

METHODS AND MATERIALS

We retrospectively identified patients treated with definitive external beam RT without hormonal therapy who had at least two itPSA measurements. We calculated the adjusted ratio of rise (ARR) in itPSA relative to the pretreatment baseline PSA for each patient. This was defined as ln(maximal itPSA + 1)/ln(baseline PSA + 1). We stratified patients according to an ARR of <1 vs. >1.1. This corresponded to an approximately <30% vs. >30% increase in PSA during RT. Univariate and multivariate analyses were performed examining for biochemical failure-free survival (BFFS) and overall survival (OS).

RESULTS

At a median follow-up of 74 months, we identified 307 patients who met our criteria. Univariate analysis revealed that patients with an ARR of <1.1 (n = 182) had statistically significant inferior BFFS and OS compared with those with an ARR of >1.1 (n = 125). The median BFFS and OS for these two groups was 51 vs. 101 months (p = 0.001) and 96 vs. 128 months (p = 0.01), respectively. On multivariate analysis, the effect of ARR on the risk of biochemical failure for patients with an ARR of <1.1 was significant (p = 0.03) only during the first year after RT. In contrast, the effect of the ARR on OS remained significant for a full 5 years (p = 0.05).

CONCLUSION

The results of our study have shown that an ARR of <1.1 predicts for inferior BFFS and OS in patients treated with RT alone. PSA measurement during RT is a novel clinical tool that could be used to identify patients who might warrant more aggressive therapeutic intervention.

Current applications for prostate-specific antigen doubling time

OBJECTIVE

To review the current status of prostate-specific antigen doubling time (PSADT) as it pertains to the evolution of prostate cancer (PCa), specifically assessing its role in the following four stages: before diagnosis, prior to definitive treatment, following treatment including salvage therapy after recurrence, and lastly, after onset of androgen-insensitive PCa.

METHODS

We searched PubMed literature for current articles on PSADT using the key words listed for this review and, where possible, selected those with significant levels of evidence that were deemed relevant, seminal, or controversial. We summarized the data regarding PSADT as a marker for diagnosis and disease characterization, as well as a predictor of progression, response to treatment, and mortality.

RESULTS

PSADT may offer an advantage in providing a more dynamic picture of tumor behavior, providing clues regarding the relative aggressiveness of the underlying pathology. Evidence points toward a role for PSADT in the management of PCa, specifically in active surveillance, disease recurrence after treatment, and in androgen-independent PCa. PSADT is an important prognostic factor that may serve as an auxiliary end point for cancer-specific survival; however, optimal cut-off points denoting risk remain debatable.

CONCLUSIONS

PCa management requires risk stratification with a combination of variables, PSADT being one of the most reliable predictors. It is now a parameter included in many predictive nomograms and in treatment guidelines for expectant management and salvage therapy.

Escalated-dose versus standard-dose conformal radiotherapy in prostate cancer: first results from the MRC RT01 randomised controlled trial

BACKGROUND

In men with localised prostate cancer, conformal radiotherapy (CFRT) could deliver higher doses of radiation than does standard-dose conventional radical external-beam radiotherapy, and could improve long-term efficacy, potentially at the cost of increased toxicity. We aimed to present the first analyses of effectiveness from the MRC RT01 randomised controlled trial.

METHODS

The MRC RT01 trial included 843 men with localised prostate cancer who were randomly assigned to standard-dose CFRT or escalated-dose CFRT, both administered with neoadjuvant androgen suppression. Primary endpoints were biochemical-progression-free survival (bPFS), freedom from local progression, metastases-free survival, overall survival, and late toxicity scores. The toxicity scores were measured with questionnaires for physicians and patients that included the Radiation Therapy Oncology Group (RTOG), the Late Effects on Normal Tissue: Subjective/Objective/Management (LENT/SOM) scales, and the University of California, Los Angeles Prostate Cancer Index (UCLA PCI) scales. Analysis was done by intention to treat. This trial is registered at the Current Controlled Trials website http://www.controlled-trials.com/ISRCTN47772397.

FINDINGS

Between January, 1998, and December, 2002, 843 men were randomly assigned to escalated-dose CFRT (n=422) or standard-dose CFRT (n=421). In the escalated group, the hazard ratio (HR) for bPFS was 0.67 (95% CI 0.53-0.85, p=0.0007). We noted 71% bPFS (108 cumulative events) and 60% bPFS (149 cumulative events) by 5 years in the escalated and standard groups, respectively. HR for clinical progression-free survival was 0.69 (0.47-1.02; p=0.064); local control was 0.65 (0.36-1.18; p=0.16); freedom from salvage androgen suppression was 0.78 (0.57-1.07; p=0.12); and metastases-free survival was 0.74 (0.47-1.18; p=0.21). HR for late bowel toxicity in the escalated group was 1.47 (1.12-1.92) according to the RTOG (grade >/=2) scale; 1.44 (1.16-1.80) according to the LENT/SOM (grade >/=2) scales; and 1.28 (1.03-1.60) according to the UCLA PCI (score >/=30) scale. 33% of the escalated and 24% of the standard group reported late bowel toxicity within 5 years of starting treatment. HR for late bladder toxicity according to the RTOG (grade >/=2) scale was 1.36 (0.90-2.06), but this finding was not supported by the LENT/SOM (grade >/=2) scales (HR 1.07 [0.90-1.29]), nor the UCLA PCI (score >/=30) scale (HR 1.05 [0.81-1.36]).

INTERPRETATION

Escalated-dose CFRT with neoadjuvant androgen suppression seems clinically worthwhile in terms of bPFS, progression-free survival, and decreased use of salvage androgen suppression. This additional efficacy is offset by an increased incidence of longer term adverse events.

Phase I Trial of Replication-competent Adenovirus-mediated Suicide Gene Therapy Combined with IMRT for Prostate Cancer

Replication-competent adenovirus-mediated suicide gene therapy is an investigational cancer treatment in which an oncolytic adenovirus armed with chemo-radiosensitizing genes is used to destroy tumor cells. Previously, we evaluated the toxicity and efficacy of this approach in two clinical trials of prostate cancer using a first-generation adenovirus. Here, we report the toxicity and preliminary efficacy of this approach in combination with intensity-modulated radiotherapy (IMRT) in patients with newly diagnosed prostate cancer using an improved, second-generation adenovirus. The investigational therapy was associated with low toxicity, and there were no dose-limiting toxicities or treatment-related serious adverse events. Relative to a previous trial using a first-generation adenovirus, there was no increase in hematologic, hepatic, gastrointestinal (GI), or genitourinary (GU) toxicities. Post-treatment prostate biopsies yielded provocative preliminary results. When the results of two similar trials were combined, 22% of evaluable patients were positive for adenocarcinoma at their last biopsy, which is better than expected (>or=40%) for this cohort of patients (P=0.038). When the results were categorized by prognostic risk, most of the treatment effect was observed in the intermediate-risk group, with 0 of 12 patients (0%) being positive for cancer at their last biopsy (P<0.01). These results further demonstrate the safety of this investigational approach and raise the possibility that it may have the potential to improve the outcome of conformal radiotherapy in select patient groups.

Prostate cancer gene therapy clinical trials

Despite recent advances in early detection and treatment, prostate cancer is still the second leading cause of cancer death in men in the United States, and approximately 27,000 men will die from it this year. Better treatments are needed for aggressive forms of localized disease and hormone-refractory metastatic disease. Recently, several gene therapy strategies have generated provocative results in early-stage clinical trials, raising the possibility that gene therapy may have the potential to affect both localized and metastatic disease. Much work lies ahead. Nevertheless, for the time being, these studies provide hope that gene therapy may someday earn a place in the management of prostate cancer.