Prostate-specific antigen velocity and survival for patients with hormone-refractory metastatic prostate carcinoma

Thresholds for PSA doubling time in men with non-metastatic castration-resistant prostate cancer

OBJECTIVES

To examine whether prostate-specific antigen doubling time (PSADT) correlates with metastases, all-cause mortality (ACM), and prostate cancer-specific mortality (PCSM) and to identify PSADT thresholds that can be used clinically for risk stratification in men with M0 castration-resistant prostate cancer (CRPC).

MATERIALS AND METHODS

We collected data on 441 men with M0 CRPC in 2000-2015 at five Veterans Affairs hospitals. Cox models were used to test the association between log-transformed PSADT and the development of metastasis, ACM and PCSM. To identify thresholds, we categorized PSADT into 3-month groups and then combined groups with similar hazard ratios (HRs).

RESULTS

The median (interquartile range) follow-up was 28.3 (14.7-49.1) months. As a continuous variable, PSADT was associated with metastases, ACM and PCSM (HR 1.40-1.68, all P < 0.001). We identified the following PSADT thresholds: <3 months; 3-8.9 months; 9-14. months; and ≥15 months. As a categorical variable, PSADT was associated with metastases, ACM and PCSM (all P < 0.001). Specifically, PSADT <3 months was associated with an approximately ninefold increased risk of metastases (HR 8.63, 95% CI 5.07-14.7) and PCSM (HR 9.29, 95% CI 5.38-16.0), and a 4.7-fold increased risk of ACM (HR 4.71, 95% CI 2.98-7.43) on multivariable analysis compared with PSADT ≥15 months. The median times to metastasis for patients with PSADT <3, 3-8.9, 9-14.9 and ≥15 months were 9, 19, 40 and 50 months, respectively.

CONCLUSION

Prostate-specific antigen doubling time was a strong predictor of metastases, ACM and PCSM in patients with M0 CRPC. As with patients at earlier disease stages, <3, 3-8.9, 9-14.9 and ≥15 months are reasonable PSADT thresholds for risk stratification in men with M0 CRPC. These thresholds can be used for selecting high-risk men for clinical trials.

Differences in characteristics of men with localised prostate cancer who demonstrate low, intermediate or high prostate-specific antigen velocity

BACKGROUND

Current diagnostic tools are inadequate for reliable prediction of prostate cancer (PCa) aggressiveness in patients with localised disease. This results in many patients being exposed to potentially unnecessary invasive treatment and its associated morbidities. In order to develop appropriate treatment strategies, it is essential to understand the differences between patients who will develop aggressive disease and those who will not.

METHODS

A longitudinal study was conducted in men with localised PCa on active surveillance for their disease in which 140 subjects were followed every 3 months for up to 5 years. Change in prostate-specific antigen (PSA) over time (PSA velocity) was used as a marker for PCa progression. Subjects were categorised as slow, intermediate and fast progressors based on tertiles of PSA velocity. Differences in baseline markers were investigated using logistic regressions. Two approaches were used, slow progressors were compared with fast progressors (model 1) and slow progressors were compared with combination of intermediate and fast progressors (model 2).

RESULTS

Aspirin was negatively associated with high PSA velocity in model 1 (odds ratio (95% confidence interval): 0.24 (0.06, 0.94), P-value = 0.04) and model 2 (odds ratio = 0.22 (0.08, 0.59), P-value = 0.003), whereas smoking was positively associated with high PSA velocity in model 1 (1.03 (0.92, 1.13), P-value = 0.01).

CONCLUSIONS

These findings highlight the role of aspirin and smoking in PCa progression. They have potential towards risk stratification as well as PCa prevention and hence need to be investigated further.

Improved overall survival trends of men with newly diagnosed M1 prostate cancer: a SWOG phase III trial experience (S8494, S8894 and S9346)

PURPOSE

Frequent prostate specific antigen testing for screening and monitoring prostate cancer has led to significant stage migration. We evaluated whether overall survival in hormone naïve patients with metastatic prostate cancer has improved during the era of prostate specific antigen use. We also assessed whether any patient subsets benefited differentially during this period.

MATERIALS AND METHODS

We compared overall survival in 3 sequential phase III trials of 3,096 men with hormone naïve, metastatic prostate cancer who received similar androgen deprivation therapy, including 2 trials performed before the prostate specific antigen era (S8494 and S8894) and the other done during this era (S9346). Overall survival was adjusted for patient and disease risk factors in the latter 2 trials. Subgroups were evaluated by interactions of risk factors with trial.

RESULTS

Median overall survival was 30 months in S8494, 33 months in S8894 and 49 months in S9346. Adjusting for risk factors, there was a 22% lower risk of death in S9346 than in S8894 (HR 0.78, 95% CI 0.70, 0.87, p <0.001). The improvement in overall survival was greater in black American men (test of interaction p = 0.008). In S8494 and S8894 median survival for black men was 27 months, and 34 and 35 months for nonblack men, respectively. This racial difference disappeared in S9346 with overall survival of 48 and 49 months in black and nonblack men, respectively.

CONCLUSIONS

Adjusting for risk factors, overall survival was significantly improved in the post-prostate specific antigen era trial. However, it cannot be concluded that this was attributable only to prostate specific antigen monitoring. Black men now have overall survival comparable to that of white men. Current estimates of survival should be used to design new trials in this population.

Evaluation of prediagnostic prostate-specific antigen dynamics as predictors of death from prostate cancer in patients treated conservatively

Prostate-specific antigen (PSA) dynamics have been proposed to predict outcome in men with prostate cancer. We assessed the value of PSA velocity (PSAV) and PSA doubling time (PSADT) for predicting prostate cancer-specific mortality (PCSM) in men with clinically localized prostate cancer undergoing conservative management or early hormonal therapy. From 1990 to 1996, 2,333 patients were identified, of whom 594 had two or more PSA values before diagnosis. We examined 12 definitions for PSADT and 10 for PSAV. Because each definition required PSA measurements at particular intervals, the number of patients eligible for each definition varied from 40 to 594 and number of events from 10 to 119. Four PSAV definitions, but no PSADT, were significantly associated with PCSM after adjustment for PSA in multivariable Cox proportional hazards regression. All four could be calculated only for a proportion of events, and the enhancements in predictive accuracy associated with PSAV had very wide confidence intervals. There was no clear benefit of PSAV in men with low PSA and Gleason grade 6 or less. Although evidence that certain PSAV definitions help to predict PCSM in the cohort exist, the value of incorporating PSAV in predictive models to assist in determining eligibility for conservative management is, at best, uncertain.

PSA surge/flare-up in patients with castration-refractory prostate cancer during the initial phase of chemotherapy

BACKGROUND

Docetaxel-based chemotherapy has shown great promise for the treatment of CRPC and is considered the current standard of care. PSA is mainly used as marker to monitor the treatment response. Several articles were published reporting an initial PSA surge/flare-up after starting chemotherapy. The cause and the impact of this phenomenon are discussed controversially. The intention of this review is to define the significance of initial PSA surge/flare-up and to increase awareness to this phenomenon in the urological community.

MATERIALS AND METHODS

A comprehensive literature search was performed in different data bases using various key words. Relevant articles and references between 1999 and 2009 were reviewed and analyzed for data on the association between chemotherapy and initial PSA surge/flare.

RESULTS

The incidence of a PSA surge/flare-up ranges according to the reported studies between 7.6% and 13.6%. A PSA surge/flare-up was reported up to 404% from baseline PSA level followed by PSA response. The median duration of a PSA surge/flare-up is 2-3 weeks and can last up to 6-8 weeks. However, the occurrence of a PSA surge/flare-up did not impact outcome and survival negatively compared to patients with an immediate PSA response.

CONCLUSIONS

A considerable portion of CRPC patients experience an initial PSA surge/flare-up under systemic chemotherapy. The definitions used for PSA surge/flare-up differ slightly in the literature. This issue needs to be solved since it might impact defining treatment response. As a PSA surge/flare-up did not impact outcome and survival negatively, chemotherapy should be continued according to the literature addressing specifically the phenomenon of a PSA surge/flare-up for a minimum of 8 weeks or 3 rounds of a 3-weekly cycle chemotherapy regimen before further decisions are made about efficacy. However, Scher et al. recommended a 12-week period drug exposure based on their results on PSA progression-free survival and overall survival. This dilemma needs to be addressed in further data analysis in order to establish a general rule regarding when to stop chemotherapy. Physicians should be aware of this effect to avoid inadequate early discontinuation of chemotherapy. The underlying mechanisms of a PSA surge/flare-up are still elusive and need further clarification.

Pretreatment prostate-specific antigen (PSA) velocity and doubling time are associated with outcome but neither improves prediction of outcome beyond pretreatment PSA alone in patients treated with radical prostatectomy

PURPOSE

Controversy exists as to whether current pretreatment prostate-specific antigen (PSA) dynamics enhance outcome prediction in patients undergoing treatment for prostate cancer. We assessed whether pretreatment PSA velocity (PSAV) or doubling time (PSADT) predicted outcome in men undergoing radical prostatectomy and whether any definition enhanced accuracy of an outcome prediction model.

PATIENTS AND METHODS

The cohort included 2,938 patients with two or more PSA values before radical prostatectomy. Biochemical recurrence (BCR) occurred in 384 patients, and metastases occurred in 63 patients. Median follow-up for patients without BCR was 2.1 years. We used univariate Cox proportional hazards regression to evaluate associations between published definitions of PSADT and PSAV with BCR and metastasis. Predictive accuracy was assessed using the concordance index.

RESULTS

On univariate analysis, two of 12 PSADT and four of 10 PSAV definitions were univariately associated with both BCR and metastasis (P < .05). One PSADT and one PSAV definition had a higher predictive accuracy for BCR over PSA alone, and four PSAV definitions improved prediction of metastasis. However, the improvements in predictive accuracy were small, associated with wide CIs, and markedly reduced if additional predictors of stage and grade were included alongside PSA. Modeling with random variables suggests that similar results would be expected by chance. CONCLUSION We found no clear evidence that any definition of PSA dynamics substantially enhances the predictive accuracy of a single pretreatment PSA alone.

Tumor growth rates derived from data for patients in a clinical trial correlate strongly with patient survival: a novel strategy for evaluation of clinical trial data

PURPOSE

The slow progress in developing new cancer therapies can be attributed in part to the long time spent in clinical development. To hasten development, new paradigms especially applicable to patients with metastatic disease are needed.

PATIENTS AND METHODS

We present a new method to predict survival using tumor measurement data gathered while a patient with cancer is receiving therapy in a clinical trial. We developed a two-phase equation to estimate the concomitant rates of tumor regression (regression rate constant d) and tumor growth (growth rate constant g).

RESULTS

We evaluated the model against serial levels of prostate-specific antigen (PSA) in 112 patients undergoing treatment for prostate cancer. Survival was strongly correlated with the log of the growth rate constant, log(g) (Pearson r = -0.72) but not with the log of the regression rate constants, log(d) (r = -0.218). Values of log(g) exhibited a bimodal distribution. Patients with log(g) values above the median had a mortality hazard of 5.14 (95% confidence interval, 3.10-8.52) when compared with those with log(g) values below the median. Mathematically, the minimum PSA value (nadir) and the time to this minimum are determined by the kinetic parameters d and g, and can be viewed as surrogates.

CONCLUSIONS

This mathematical model has applications to many tumor types and may aid in evaluating patient outcomes. Modeling tumor progression using data gathered while patients are on study, may help evaluate the ability of therapies to prolong survival and assist in drug development.

A contemporary prognostic nomogram for men with hormone-refractory metastatic prostate cancer: a TAX327 study analysis

PURPOSE

To develop a prognostic model and nomogram using baseline clinical variables to predict death among men with metastatic hormone-refractory prostate cancer (HRPC).

EXPERIMENTAL DESIGN

TAX327 was a clinical trial that randomized 1,006 men with metastatic HRPC to receive every three week or weekly docetaxel or mitoxantrone, each with prednisone. We developed a multivariate Cox model and nomogram to predict survival at 1, 2, and 5 years.

RESULTS

Ten independent prognostic factors other than treatment group were identified in multivariate analysis: (a) presence of liver metastases [hazard ratio (HR), 1.66; P = 0.019], (b) number of metastatic sites (HR, 1.63 if > or =2 sites; P = 0.001), (c) clinically significant pain (HR, 1.48; P < 0.0001), (d) Karnofsky performance status (HR, 1.39 if < or =70; P = 0.016), (e) type of progression (HR, 1.37 for measurable disease progression and 1.29 for bone scan progression; P = 0.005 and 0.01, respectively), (f) pretreatment prostate-specific antigen (PSA) doubling time (HR, 1.19 if <55 days; P = 0.066), (g) PSA (HR, 1.17 per log rise; P < 0.0001), (h) tumor grade (HR, 1.18 for high grade; P = 0.069), (i) alkaline phosphatase (HR, 1.27 per log rise; P < 0.0001), and (j) hemoglobin (HR, 1.11 per unit decline; P = 0.004). A nomogram was developed based on this multivariate model and validated internally using bootstrap methods, with a concordance index of 0.69.

CONCLUSIONS

This multivariate model identified several new independent prognostic factors in men with metastatic HRPC, including PSA doubling time, and led to the successful development of a clinically applicable nomogram. External prospective validation may support the wider use of this prognostic baseline model for men with HRPC treated with chemotherapy.

Progression after docetaxel-based chemotherapy in androgen-independent prostate cancer

OBJECTIVE

To assess the clinical pattern of progression and prostate-specific antigen doubling time (PSA-DT) after exposure to docetaxel-based chemotherapy in patients with androgen-independent prostate cancer (AIPC).

PATIENTS AND METHODS

Fifty-five patients received docetaxel-based chemotherapy; data were collected retrospectively from three different departments. Progression was known in 44 (79%) and the PSA-DT was available in 33 patients.

RESULTS

Of the 29 patients with soft-tissue and soft-tissue plus bone metastases, 22 (76%) developed soft-tissue progression. Among the 35 patients with bone and bone plus soft-tissue metastases, 27 (77%) had osseous progression. There was no difference between the PSA-DT at progression before and after docetaxel-based therapy (mean 3.1 vs 2.7 months, P = 0.592, Student's t-test.). However, the median (range) PSA-DT at progression after docetaxel-based therapy was 0.84 (0.3-4) months in patients with a PSA response, significantly shorter than the median of 3.1 (0.3-12) months of patients with no biochemical response (P = 0.002, Student's t-test). The PSA-DT dynamics at progression had no effect on survival (P = 0.63, log-rank test).

CONCLUSION

The pattern of progression after docetaxel-based chemotherapy is predominantly osseous in patient with bone metastases and mostly soft-tissue in those with soft-tissue disease. Progression after docetaxel-based chemotherapy in AIPC does not modify the PSA-DT before docetaxel. Evaluation of a larger population is needed to assess the clinical relevance of PSA dynamics after docetaxel therapy.

Changes of biochemical markers of bone turnover and YKL-40 following hormonal treatment for metastatic prostate cancer are related to survival

PURPOSE

Elevated serum levels of biochemical markers of bone turnover and YKL-40 in patients with metastatic prostate cancer (PC) at the time of diagnosis are associated to poor prognosis. In this study, we evaluated the value of these biomarkers in monitoring the patients during hormonal treatment.

EXPERIMENTAL DESIGN

Serum procollagen type I N-terminal propeptide (PINP), bone-specific alkaline phosphatase (BAP), CTX-I, and YKL-40 were determined by ELISA in a longitudinal study of 106 patients with metastatic PC during treatment with total androgen ablation or parenteral estrogen. Serum samples were collected with 3 months interval. Median observation time was 4.9 years (range, 3.6-6.2). A total of 78 patients died (64 within 7 months following the last blood sampling).

RESULTS

After 6 months treatment, serum PINP, BAP, and YKL-40 decreased (P < 0.0001), but not serum CTX-I compared with baseline values. Univariate Cox analysis showed that serum PINP at 6 months [log transformed and treated as a continuous variable; hazard ratio (HR), 2.2; P < 0.0001], serum BAP (HR, 1.8; P < 0.0001), and serum CTX-I (HR, 2.4; P < 0.0001), but not serum YKL-40 (HR, 1.4; P = 0.16) were associated with survival. Multivariate Cox analysis including the biomarkers 6 months after the start of treatment showed that Soloway score (HR, 3.9; P = 0.013), WHO tumor grade (HR, 3.9; P = 0.004), and serum PINP (HR, 2.2; P < 0.0001) were independent prognostic variables of survival. Scoring the biomarkers during treatment as time-dependent covariates in univariate Cox regression analysis showed that increases in serum PINP (HR, 2.0; P < 0.0001), BAP (HR, 2.1; P < 0.0001), and YKL-40 (HR, 2.1; P < 0.0001) were predictors of early death.

CONCLUSIONS

Serial monitoring of serum PINP, BAP, CTX-I, and YKL-40 in metastatic PC patients during hormonal treatment provided information of prognosis.

Effect of Definition of Preradiotherapy Prostate-Specific Antigen Velocity on Its Association with Prostate Cancer-Specific Mortality and All-Cause Mortality

OBJECTIVES

An increasing prostate-specific antigen (PSA) velocity (PSAV) is associated with a shorter time to prostate cancer-specific mortality (PCSM) after definitive local therapy. This study examined the effect on this association when the PSAV was estimated using all PSA values (PSAV-all) instead of the PSA values within 18 months before diagnosis (PSAV-18).

METHODS

We studied 358 men (median age 71.2) with clinically localized prostate cancer treated with external beam radiotherapy to a dose of 70.35 Gy from 1989 to 2002. The median follow-up was 4.0 years. The Cox and Gray's multivariate regression analyses were used to evaluate the association between PSAV and the interval to PSA recurrence, all-cause mortality, and PCSM, adjusting for known prognostic factors.

RESULTS

The median PSAV-18 and PSAV-all was 1.50 ng/mL/yr (interquartile range 0.74 to 3.82) and 1.20 ng/mL/yr (interquartile range 0.69 to 3.34), respectively. Of the 358 men, 226 (63%) had only two PSA values; therefore, the estimation of their PSAV was the same, irrespective of the method used. Remarkably, despite the identical estimates for PSAV in 63% of the men in this study, after adjusting for known prognostic factors, the hazard ratios describing the significant associations with the interval to PSA recurrence, PCSM, and all-cause mortality increased and the associated P values decreased using PSAV-18 compared with PSAV-all.

CONCLUSIONS

The results of this study have shown that the PSAV estimated using the pretreatment PSA values obtained approximately 18 months before diagnosis compared with using all previous PSA values provides a stronger association with the interval to PSA recurrence, PCSM, and all-cause mortality after RT.

The quinoline-3-carboxamide anti-angiogenic agent, tasquinimod, enhances the anti-prostate cancer efficacy of androgen ablation and taxotere without effecting serum PSA directly in human xenografts

PURPOSE

Tasquinimod is a second-generation orally active quinoline-3-carboxamide analog with enhanced potency against prostate cancer via its anti-angiogenic activity. It is presently undergoing clinical trials. Androgen ablation and taxanes are standard therapies for metastatic prostate cancer. This raises the issue of whether combining tasquinimod with either of these approaches enhances therapeutic efficacy.

EXPERIMENTAL DESIGN

The tumor growth of a series of human prostate cancer xenografts (CWR-22Rv1, CWR-22R-H, LAPC-4, LNCaP, PC-3 and DU-145) in male nude mice given nothing versus tasquinimod alone or in combination with androgen ablation or with androgen ablation plus taxotere were evaluated as model systems to resolve these issues.

RESULTS

These studies documented that daily oral treatment with tasquinimod consistently, statistically (P < 0.05) inhibited the tumor growth of each of the xenografts in a dose-dependent manner via an anti-angiogenic response as monitored by a significant (P < 0.05) decrease in the tumor blood vessel density. Tasquinimod's anti-prostate cancer efficacy is enhanced when combined with androgen ablation and this enhancement was observed even when androgen ablation was either subsequent to or proceeded by tasquinimod treatment. In addition, tasquinimod also enhanced the tumor growth inhibition and survival when combined with androgen ablation plus taxotere. Companion studies documented that tasquinimod has no direct effect on serum PSA in these xenografts.

CONCLUSIONS

These results documented that differences in serum PSA in tasquinimod-treated hosts are related to inhibition in tumor growth. This suggests that in clinical trials, changes in PSA slope or doubling time are indicative of therapeutic response to tasquinimod.

Improving the outcome of patients with castration-resistant prostate cancer through rational drug development

Castration-resistant prostate cancer (CRPC) is now the second most common cause of male cancer-related mortality. Although docetaxel has recently been shown to extend the survival of patients with CRPC in two large randomised phase III studies, subsequent treatment options remain limited for these patients. A greater understanding of the molecular causes of castration resistance is allowing a more rational approach to the development of new drugs and many new agents are now in clinical development. Therapeutic targets include the adrenal steroid synthesis pathway, androgen receptor signalling, the epidermal growth factor receptor family, insulin growth factor-1 receptor, histone deacetylase, heat shock protein 90 and the tumour vasculature. Drugs against these targets are giving an insight into the molecular pathogenesis of this disease and promise to improve patient quality of life and survival. Finally, the recent discovery of chromosomal translocations resulting in the upregulation of one of at least 3 ETS genes (ERG, ETV1, ETV4) may lead to novel agents for the treatment of this disease.

Therapeutic Vaccines for Prostate Cancer

Prostate cancer is the most common, noncutaneous cancer for men in the U.S., leading to more than 30,000 deaths a year. Vaccines for prostate cancer, which for several years have been shown to generate immunologic responses, are beginning to show significant clinical promise. At present, numerous therapeutic options are being investigated, including autologous and allogeneic whole-tumor cell vaccines, dendritic cell vaccines, and poxvirus-based vaccines. Advances in basic immunology have translated into new, more complex therapeutic strategies. The findings from current trials and the demonstrated potential to combine vaccines with conventional therapies herald a promising future for the treatment of prostate cancer. This review highlights recent advances and clinical trials in immunotherapy for prostate cancer, along with current thoughts on immunologic and clinical monitoring of these trials.