Prognostic significance of reverse transcriptase polymerase chain reaction for prostate-specific antigen in metastatic prostate cancer: a nested study within CALGB 9583

Impact of Circulating Tumor Cell-Expressed Prostate-Specific Membrane Antigen and Prostate-Specific Antigen Transcripts in Different Stages of Prostate Cancer

PURPOSE

Prostate-specific membrane antigen (PSMA)-based images, which visually quantify PSMA expression, are used to determine prostate cancer micrometastases. This study evaluated whether a circulating tumor cell (CTC)-based transcript platform, including PSMA mRNA, could help identify potential prognostic markers in prostate cancer.

EXPERIMENTAL DESIGN

We prospectively enrolled 21 healthy individuals and 247 patients with prostate cancer [localized prostate cancer (LPCa), n = 94; metastatic hormone-sensitive prostate cancer (mHSPC), n = 44; and metastatic castration-resistant prostate cancer (mCRPC), n = 109]. The mRNA expression of six transcripts [PSMA, prostate-specific antigen (PSA), AR, AR-V7, EpCAM, and KRT 19] from CTCs was measured, and their relationship with biochemical recurrence (BCR) in LPCa and mCRPC progression-free survival (PFS) rate in mHSPC was assessed. PSA-PFS and radiological-PFS were also calculated to identify potential biomarkers for predicting androgen receptor signaling inhibitor (ARSI) and taxane-based chemotherapy resistance in mCRPC.

RESULTS

CTC detection rates were 75.5%, 95.3%, and 98.0% for LPCa, mHSPC, and mCRPC, respectively. In LPCa, PSMA [hazard ratio (HR), 3.35; P = 0.028) and PSA mRNA (HR, 1.42; P = 0.047] expressions were associated with BCR. Patients with mHSPC with high PSMA (HR, 4.26; P = 0.020) and PSA mRNA (HR, 3.52; P = 0.042) expressions showed significantly worse mCRPC-PFS rates than those with low expression. Increased PSA and PSMA mRNA expressions were significantly associated with shorter PSA-PFS and radiological PFS in mCPRC, indicating an association with drug resistance.

CONCLUSIONS

PSMA and PSA mRNA expressions are associated with BCR in LPCa. In advanced prostate cancer, PSMA and PSA mRNA can also predict rapid progression from mHSPC to mCRPC and ARSI or taxane-based chemotherapy resistance.

External Validation of a Prognostic Model of Overall Survival in Men With Chemotherapy-Naïve Metastatic Castration-Resistant Prostate Cancer

PURPOSE

We have previously developed and externally validated a prognostic model of overall survival (OS) in men with metastatic, castration-resistant prostate cancer (mCRPC) treated with docetaxel. We sought to externally validate this model in a broader group of men with docetaxel-naïve mCRPC and in specific subgroups (White, Black, Asian patients, different age groups, and specific treatments) and to classify patients into validated two and three prognostic risk groupings on the basis of the model.

METHODS

Data from 8,083 docetaxel-naïve mCRPC men randomly assigned on seven phase III trials were used to validate the prognostic model of OS. We assessed the predictive performance of the model by computing the time-dependent area under the receiver operating characteristic curve (tAUC) and validated the two-risk (low and high) and three-risk prognostic groups (low, intermediate, and high).

RESULTS

The tAUC was 0.74 (95% CI, 0.73 to 0.75), and when adjusting for the first-line androgen receptor (AR) inhibitor trial status, the tAUC was 0.75 (95% CI, 0.74 to 0.76). Similar results were observed by the different racial, age, and treatment subgroups. In patients enrolled on first-line AR inhibitor trials, the median OS (months) in the low-, intermediate-, and high-prognostic risk groups were 43.3 (95% CI, 40.7 to 45.8), 27.7 (95% CI, 25.8 to 31.3), and 15.4 (95% CI, 14.0 to 17.9), respectively. Compared with the low-risk prognostic group, the hazard ratios for the high- and intermediate-risk groups were 4.3 (95% CI, 3.6 to 5.1; P < .0001) and 1.9 (95% CI, 1.7 to 2.1; P < .0001).

CONCLUSION

This prognostic model for OS in docetaxel-naïve men with mCRPC has been validated using data from seven trials and yields similar results overall and across race, age, and different treatment classes. The prognostic risk groups are robust and can be used to identify groups of patients for enrichment designs and for stratification in randomized clinical trials.

Hepatic Cancer Stem Cells: Molecular Mechanisms, Therapeutic Implications, and Circulating Biomarkers

Hepatocellular carcinoma (HCC) is one of the deadliest cancers. HCC is associated with multiple risk factors and is characterized by a marked tumor heterogeneity that makes its molecular classification difficult to apply in the clinics. The lack of circulating biomarkers for the diagnosis, prognosis, and prediction of response to treatments further undermines the possibility of developing personalized therapies. Accumulating evidence affirms the involvement of cancer stem cells (CSCs) in tumor heterogeneity, recurrence, and drug resistance. Owing to the contribution of CSCs to treatment failure, there is an urgent need to develop novel therapeutic strategies targeting, not only the tumor bulk, but also the CSC subpopulation. Clarification of the molecular mechanisms influencing CSC properties, and the identification of their functional roles in tumor progression, may facilitate the discovery of novel CSC-based therapeutic targets to be used alone, or in combination with current anticancer agents, for the treatment of HCC. Here, we review the driving forces behind the regulation of liver CSCs and their therapeutic implications. Additionally, we provide data on their possible exploitation as prognostic and predictive biomarkers in patients with HCC.

Association of AR-V7 and Prostate-Specific Antigen RNA Levels in Blood with Efficacy of Abiraterone Acetate and Enzalutamide Treatment in Men with Prostate Cancer

PURPOSE

We evaluated the association of PSA and androgen receptor splice variant-7 (AR-V7) transcript levels in patients' blood with time to treatment failure (TTF) and overall survival (OS) with abiraterone acetate and/or enzalutamide treatment in castration-resistant prostate cancer (CRPC) patients.

EXPERIMENTAL DESIGN

RNA levels of AR-V7 and PSA in peripheral blood collected before treatment were quantified using droplet digital-PCR in retrospective cohorts treated with abiraterone acetate (N = 81) or enzalutamide (N = 51) for CRPC. Multivariable Cox regression adjusted for known prognostic factors was used for analyses.

RESULTS

PSA transcripts were detected in 57% of abiraterone acetate-treated patients and in 63% of enzalutamide-treated patients. PSA-positive patients had a shorter TTF than PSA-negative patients [adjusted HR = 2.27 (95% confidence interval (CI) 1.26-4.10) and 2.60 (95% CI, 1.19-5.69); P = 0.006 and 0.017 in abiraterone acetate and enzalutamide cohorts, respectively]. Patients with a higher-AR-V7 transcript level had a shorter TTF with abiraterone acetate and enzalutamide in univariate analysis (median 8.0 months vs. 15.6 months, P = 0.046 in abiraterone acetate-cohort and 3.6 months vs. 5.6 months; P = 0.050 in enzalutamide cohort). In multivariable models, the association with TTF remained significant in the enzalutamide cohort (adjusted HR = 2.02; 95% CI, 1.01-4.05; P = 0.048), but statistically insignificant in the abiraterone acetate cohort. In both cohorts, we observed potential prognostic value of both PSA and AR-V7 RNA expression on OS; patients with detectable PSA transcripts and high AR-V7 predicted the poorest OS.

CONCLUSIONS

PSA and AR-V7 transcripts in blood potentially serve as biomarkers predicting TTF and OS with abiraterone acetate or enzalutamide treatment. If validated prospectively, their detection could be facilitated without isolation of circulating tumor cells. Clin Cancer Res; 23(3); 726-34. ©2016 AACR.

Circulating tumor cell biomarker panel as an individual-level surrogate for survival in metastatic castration-resistant prostate cancer

PURPOSE

Trials in castration-resistant prostate cancer (CRPC) need new clinical end points that are valid surrogates for survival. We evaluated circulating tumor cell (CTC) enumeration as a surrogate outcome measure.

PATIENTS AND METHODS

Examining CTCs alone and in combination with other biomarkers as a surrogate for overall survival was a secondary objective of COU-AA-301, a multinational, randomized, double-blind phase III trial of abiraterone acetate plus prednisone versus prednisone alone in patients with metastatic CRPC previously treated with docetaxel. The biomarkers were measured at baseline and 4, 8, and 12 weeks, with 12 weeks being the primary measure of interest. The Prentice criteria were applied to test candidate biomarkers as surrogates for overall survival at the individual-patient level.

RESULTS

A biomarker panel using CTC count and lactate dehydrogenase (LDH) level was shown to satisfy the four Prentice criteria for individual-level surrogacy. Twelve-week surrogate biomarker data were available for 711 patients. The abiraterone acetate plus prednisone and prednisone-alone groups demonstrated a significant survival difference (P = .034); surrogate distribution at 12 weeks differed by treatment (P < .001); the discriminatory power of the surrogate to predict mortality was high (weighted c-index, 0.81); and adding the surrogate to the model eliminated the treatment effect on survival. Overall, 2-year survival of patients with CTCs < 5 (low risk) versus patients with CTCs ≥ 5 cells/7.5 mL of blood and LDH > 250 U/L (high risk) at 12 weeks was 46% and 2%, respectively.

CONCLUSION

A biomarker panel containing CTC number and LDH level was shown to be a surrogate for survival at the individual-patient level in this trial of abiraterone acetate plus prednisone versus prednisone alone for patients with metastatic CRPC. Additional trials are ongoing to validate the findings.

Circulating tumour cells: the evolving concept and the inadequacy of their enrichment by EpCAM-based methodology for basic and clinical cancer research

Increasing evidence suggests that circulating tumour cells (CTCs) are responsible for metastatic relapse and this has fuelled interest in their detection and quantification. Although numerous methods have been developed for the enrichment and detection of CTCs, none has yet reached the 'gold' standard. Since epithelial cell adhesion molecule (EpCAM)-based enrichment of CTCs offers several advantages, it is one of the most commonly used and has been adapted for high-throughput technology. However, emerging evidence suggests that CTCs are highly heterogeneous: they consist of epithelial tumour cells, epithelial-to-mesenchymal transition (EMT) cells, hybrid (epithelial/EMT(+)) tumour cells, irreversible EMT(+) tumour cells, and circulating tumour stem cells (CTSCs). The EpCAM-based approach does not detect CTCs expressing low levels of EpCAM and non-epithelial phenotypes such as CTSCs and those that have undergone EMT and no longer express EpCAM. Thus, the approach may lead to underestimation of the significance of CTCs, in general, and CTSCs and EMT(+) tumour cells, in particular, in cancer dissemination. Here, we provide a critical review of research literature on the evolving concept of CTCs and the inadequacy of their enrichment by EpCAM-based technology for basic and clinical cancer research. The review also outlines future perspectives in the field.

Measurement of affective and activity pain interference using the Brief Pain Inventory (BPI): Cancer and Leukemia Group B 70903

OBJECTIVE

The Brief Pain Inventory (BPI) was designed to yield separate scores for pain intensity and interference. It has been proposed that the pain interference factor can be further broken down into unique factors of affective (e.g., mood) and activity (e.g., work) interference. The purpose of this analysis was to confirm this affective/activity interference dichotomy.

PATIENTS AND METHODS

A retrospective confirmatory factor analysis was completed for a sample of 184 individuals diagnosed with castrate-resistant prostate cancer (age 40-86, mean = 65.46, 77% White non-Hispanic) who had been administered the BPI as part of Cancer and Leukemia Group B trial 9480. A one-factor model was compared against two-factor and three-factor models that were developed based on the design of the instrument.

RESULTS

Root mean squared error of approximation (0.075), comparative fit index (0.971), and change in chi-square, given the corresponding change in degrees of freedom (13.33, P < 0.05) values for the three-factor model (i.e., pain intensity, activity interference, and affective interference), were statistically superior in comparison with the one- and two-factor models. This three-factor structure was found to be invariant across age, mean prostate-specific antigen, and hemoglobin levels.

CONCLUSIONS

These results confirm that the BPI can be used to quantify the degree to which pain separately interferes with affective and activity aspects of a patient's everyday life. These findings will provide clinical trialists, pharmaceutical sponsors, and regulators with confidence in the flexibility of the BPI as they consider the use of this instrument to assist with understanding the patient experience as it relates to treatment.

Detection of α-Methylacyl-Coenzyme-A Racemase Transcripts in Blood and Urine Samples of Prostate Cancer Patients

BACKGROUND

Alpha-methylacyl-coenzyme-A racemase (AMACR) has been shown to be a highly specific marker for prostate cancer cells, even in the earliest stages of malignant progression. It is expressed at much higher levels than prostate-specific antigen (PSA) in malignant tissues, and is not expressed at appreciable levels in normal prostatic epithelium. In this study, we demonstrate the quantitative detection of AMACR transcripts in peripheral blood of prostate cancer patients using real-time RT-PCR. In addition, we have undertaken a pilot study to demonstrate the potential application of this technique for the detection of prostate tumor cells in urine samples from patients with prostate cancer.

METHODS

A real-time RT-PCR assay was developed for detection of the expression of AMACR in prostate cancer patients. Blood samples from 163 patients were tested at various stages of disease progression, with or without therapy. Blood specimens from patients with benign prostate disorders and other types of cancer were also evaluated.

RESULTS

In 28 of 58 samples from patients with known metastatic disease who were undergoing treatment, an AMACR expression signal above the cut-off value was detected, consistent with the presence of circulating tumor cells. In 39 of 88 patients with presumptive organ-confined disease, there was evidence of low levels of circulating tumor cells. Comparison of AMACR RT-PCR with known serum PSA values indicated that a combination of these parameters significantly increased the sensitivity for detection of progressive disease. In a pilot study analyzing urine samples from seven prostate cancer patients, elevated AMACR expression levels were detected in the urine sediments of four of six stage-T1 prostate cancer patients and in the one patient with stage-T2 prostate cancer.

CONCLUSION

The data presented in this study indicates that AMACR real-time RT-PCR may aid in the detection and staging of prostate cancer.

Immunomagnetic separation technologies

The largest difficulty one faces in the development of technology for detection of circulating tumor cells (CTCs) is whether or not tumor cells are present in the blood and at what frequency. Although the introduction of the validated CellSearch system for CTC enumeration has facilitated CTC research the question remains whether CTC are missed or whether the CTC that are reported are indeed clinically relevant. To fulfill the promise of CTC as a real-time liquid biopsy they will need to be present in the blood volume tested and need to be isolated without losing the ability to test the presence of treatment targets. To characterize a sufficiently large number of CTCs in the majority of cancer patients the volume of blood needed is simply too large to process without enrichment prior to detection. Here, we review the detection of CTCs by flow cytometry and fluorescence microscopy with and without immunomagnetic enrichment.

Current paradigms and evolving concepts in metastatic castration-resistant prostate cancer

Until recently, docetaxel-based therapy represented the only therapy shown to prolong survival in patients with metastatic castration-resistant prostate cancer (mCRPC). The past year and a half has been marked by unprecedented progress in treatments for this disease. Three positive phase III clinical trials have emerged, each evaluating agents (sipuleucel-T, cabazitaxel and abiraterone) with distinct mechanisms of action. Herein, the three pivotal trials are described alongside both past and current large phase III studies conducted in this mCRPC. The overall survival for patients with mCRPC treated in current clinical trials is considerably longer than noted in the past. We note that more recent trials with older agents have also shown improved survival and discuss potential non-therapeutic biases that influence this critical measure of outcome. The necessity for utilizing randomized trials when evaluating new therapeutics is emphasized given the changing prognosis in this mCRPC.

Detection of circulating tumor cells: Clinical relevance of a novel metastatic tumor marker

Most cancer-related deaths are caused by the hematogenous spread of cancer cells to distant organs and their subsequent metastasis. During the early stages of the metastatic cascade, cancer cells disseminate from the primary site via the lymphatic vessels and/or by hematogenous routes. Circulating tumor cells (CTCs), cancer cells that have disseminated into the systemic circulation, may be a predictor of poor prognosis in several carcinomas. An understanding of the molecular mechanisms involved in the blood-borne dissemination of cancer cells may help to clarify the process of metastasis and provide a powerful and non-invasive approach for anticancer treatments that are tailored to individual patients.

Infiltration of tumour-associated macrophages in prostate biopsy specimens is predictive of disease progression after hormonal therapy for prostate cancer

OBJECTIVE

• To evaluate tumour-associated macrophage (TAM) infiltration in prostate biopsy specimens as a possible prognostic factor for prostate cancer (PCa) after hormonal therapy.

PATIENTS AND METHODS

• Immunostaining of TAMs in prostate biopsy specimens was performed using a monoclonal antibody CD68 for 71 patients having PCa treated with hormonal therapy. • Six microscopic (×400) fields around the cancer foci were selected for TAM counting.

RESULTS

• The median value of serum prostate-specific antigen (PSA) was 50.1 ng/mL, and the median TAM count was 22. • Recurrence-free survival was significantly better in patients with fewer TAMs (<22) than in those with higher numbers of TAMs (≥22) (P < 0.001). • TAM count was higher in those with higher serum PSA (PSA), higher Gleason score, clinical T stage or those with PSA failure. Cox multivariate analysis showed that TAM count is one of the prognostic factors for PCa treated by hormonal therapy (P < 0.0001).

CONCLUSION

• TAM infiltration in prostate needle biopsy specimens is a useful predictive factor for PSA failure or progression of PCa after hormonal therapy.

Investigation of risk factors for prostate cancer patients with bone metastasis based on clinical data

It has not yet been determined whether certain types of prostate cancer with bone metastasis (M1b PC) are associated with a poor outcome. The present study retrospectively assessed the potential significance of various clinical data in predicting the outcome of M1b PC. The subjects were 104 patients who attended our hospital and received a diagnosis of M1b PC between January 1998 and December 2006. The age of the subjects ranged from 51 to 91 years (median 74). The observation period ranged from 4 to 122 months (median 43). The parameters investigated were T classification, N classification, Gleason score (GS), pre-treatment prostate-specific antigen (PSA) level, extent of disease (EOD) grade, alkaline phosphatase (ALP), lactate dehydrogenase (LDH), calcium and hemoglobin (Hb) levels and platelet count. The 5-year cause-specific survival rate was 56.6% and the 10-year cause-specific survival rate was 34.9%. Log-rank test and Cox univariate analysis identified the following factors with statistically significant differences: pre-treatment PSA level ≥192, N1, GS ≥8, EOD grade 3+4, high LDH, high ALP and low Hb. Multivariate Cox proportional hazard analysis identified the factors GS ≥8 and high LDH with significant differences. The hazard ratio was 4.967 and 2.728, respectively, and the probability value (P) was 0.029 and 0.004, respectively. When the subjects with GS ≥8 and high LDH were classified as the high-risk group, the 5-year cause-specific survival rate was 24.6%. The outcome was significantly poorer in this group (P<0.0001) than in the other group, which had a 5-year cause-specific survival rate of 67.7%. The present study showed that patients with M1b PC with GS ≥8 and high LDH have a very poor outcome and thus should be treated as a high-risk group requiring close follow-up.

The development of risk groups in men with metastatic castration-resistant prostate cancer based on risk factors for PSA decline and survival

AIMS OF THE STUDY

There are no known predictive factors of response in men receiving chemotherapy for metastatic castration-resistant prostate cancer (mCRPC). We investigated pre-treatment factors that predicted a 30% PSA decline (30% PSAD) within 3 months of starting chemotherapy, and assessed performance of a risk group classification in predicting PSA declines and overall survival (OS) in men with mCRPC.

METHODS

In TAX327, 1006 men with mCRPC were randomized to receive docetaxel (D) in two schedules, or mitoxantrone (M), each with prednisone: 989 provided data on PSA decline within 3 months. Predictive factors for a 30% PSAD were identified using multivariable regression in D-treated men (n=656) and validated in M-treated men (n=333).

RESULTS

Four independent risk factors predicted 30% PSAD: pain, visceral metastases, anaemia and bone scan progression. Risk groups (good: 0-1 factors, intermediate: 2 factors and poor: 3-4 factors) were developed with median OS of 25.7, 18.7 and 12.8 months (p<0.0001); 30% PSAD in 78%, 66% and 58% of men (p<0.001); and measurable disease response in 19%, 9% and 5% of men (p=0.018), respectively. In the validation cohort, similar predictive ability was noted for 30% PSAD, tumour response and OS. PCWG2 subtypes were also predictive but resulted in unequal grouping. C-indices were 0.59 and 0.62 for 30% PSAD and OS in the validation dataset, respectively.

CONCLUSIONS

Risk groups have been identified and validated that predict PSAD and OS in men with mCRPC and may facilitate evaluation of new systemic regimens warranting definitive testing in comparison with docetaxel and prednisone. Prospective validation of this classification system is needed.

Circulating tumor cells in patients with castration-resistant prostate cancer baseline values and correlation with prognostic factors

PURPOSE

Circulating tumor cells (CTC) have been recently accepted by the Food and Drug Administration of the United States as a prognostic tool in advanced prostate cancer. However, a number of questions remain about the use of the test. The optimal clinical cut-off has never been determined. Also, the predictive value of CTCs in the setting of low-burden advanced prostate cancer has not been evaluated. Herein we describe our experience with the CellSearch method of CTC enumeration.

EXPERIMENTAL DESIGN

CTCs enumerated from 100 patients with castration-resistant prostate cancer were correlated with clinicopathologic characteristics and conventional biomarkers, such as prostate-specific antigen and lactate dehydrogenase. Patients received ongoing medical oncologic follow-up for up to 26 months, and overall survival status was documented.

RESULTS

Forty-nine of the patients (49%) were alive at the end of the study. CTC counts correlate well with overall survival (P < 0.001) but are also tightly interrelated to other biomarkers. Threshold analysis identified 4 CTC/7.5 cc (compared with the approved value of 5) as an optimal cut-off value with respect to correlation with survival outcomes as well as predictive of metastatic disease. Univariate analysis confirmed a tight interrelationship between cut-off CTC values and biomarkers. Multivariate analysis with bootstrap sampling validation identified lactate dehydrogenase (P = 0.002) and CTCs (P = 0.001) as independently prognostically significant.

CONCLUSIONS

Baseline CTC values provide important prognostic information and specific prediction of metastatic disease. Their presence correlates with classic biomarkers.

What is the real impact of bone pain on survival in patients with metastatic hormone-refractory prostate cancer treated with docetaxel?

OBJECTIVES

To determine the benefit of starting early chemotherapy with docetaxel (the recommended first-line treatment) for patients with asymptomatic metastatic hormone-refractory prostate cancer (HRPC).

PATIENTS AND METHODS

Data were analysed from 145 patients with HRPC treated with chemotherapy between February 2000 and June 2002 in one French centre. Eligible patients were categorized into three groups according to the bone pain at baseline, i.e. minimal/no pain, mild, and moderate/severe pain. The primary endpoint was the effect of bone pain on overall survival (OS).

RESULTS

Docetaxel was administered to 67% of patients. The risk of death was 1.56 and 2.11 times higher for patients with mild or moderate/severe pain than for those with minimal/no pain (P = 0.027). The median (95% confidence interval (CI)) OS was 23.1 (18.5-27.6) and 14.1 (8.9-19.2) months (P = 0.001, log-rank-test) for patients with minimal pain or no pain treated with docetaxel-based chemotherapy compared with mitoxantrone, respectively. The prostate-specific antigen doubling time (PSA-DT) had a significant effect on OS in patients with minimal/no pain, with a median of 32.4 and 16.5 months for a PSA-DT of >or=45 and <45 days, respectively (P < 0.001).

CONCLUSIONS

Our results suggest that patients with HRPC and minimal or no bone pain could have better survival than those with mild pain or moderate to severe pain, independent of the treatment administered. In addition, patients with HRPC and minimal or no bone pain treated with docetaxel-based chemotherapy have a significantly better OS than those treated with mitoxantrone. The PSA-DT can be useful to identify asymptomatic patients who are candidates for early treatment.

DETECTION OF DISSEMINATED TUMOR CELLS IN PERIPHERAL BLOOD

Metastases are the major cause of cancer-related deaths in patients with solid epithelial malignancies, such as breast, colorectal and prostate carcinomas. Hematogenous spreading of tumor cells from a primary tumor can be considered as a crucial step in the metastasis cascade leading eventually to the formation of clinically manifest metastases. Consequently, as shown in recent studies, the detection of disseminated tumor cells in peripheral blood might be of clinical relevance with respect to individual patient prognosis and staging or monitoring of therapy. However, the rarity of disseminated tumor cells in peripheral blood renders the application of sensitive techniques mandatory for their detection. The emergence of highly sophisticated reverse transciptase-polymerase chain reaction (RT-PCR) assays, combining a preanalytical enrichment step with the assessment of multiple molecular tumor markers expressed in disseminated tumor cells, provides a powerful tool in detecting disseminated tumor cells with high sensitivity and specificity. This review will discuss currently used tumor markers as well as experimental means to enhance the sensitivity and specificity of RT-PCR assays to detect disseminated tumor cells in the peripheral blood of patients with breast, colorectal, and prostate cancers, and their clinical relevance assessed in recent studies.

Review: Biological relevance of disseminated tumor cells in cancer patients

The prognosis of cancer patients is largely determined by the occurrence of distant metastases. In patients with primary tumors, this relapse is mainly due to clinically occult micrometastasis present in secondary organs at primary diagnosis but not detectable even with high resolution imaging procedures. Sensitive and specific immunocytochemical and molecular assays enable the detection and characterization of disseminated tumor cells (DTC) at the single cell level in bone marrow (BM) as the common homing site of DTC and circulating tumor cells (CTC) in peripheral blood. Because of the high variability of results in DTC and CTC detection, there is an urgent need for standardized methods. In this review, we will focus on BM and present currently available methods for the detection and characterization of DTC. Furthermore, we will discuss data on the biology of DTC and the clinical relevance of DTC detection. While the prognostic impact of DTC in BM has clearly been shown for primary breast cancer patients, less is known about the clinical relevance of DTC in patients with other carcinomas. Current findings suggest that DTC are capable to survive chemotherapy and persist in a dormant nonproliferating state over years. To what extent these DTC have stem cell properties is subject of ongoing investigations. Further characterization is required to understand the biology of DTC and to identify new targets for improved risk prevention and tailoring of therapy. Our review will focus on breast, colon, lung, and prostate cancer as the main tumor entities in Europe and the United States.

Circulating tumor cell number and prognosis in progressive castration-resistant prostate cancer

PURPOSE

The development of tumor-specific markers to select targeted therapies and to assess clinical outcome remains a significant area of unmet need. We evaluated the association of baseline circulating tumor cell (CTC) number with clinical characteristics and survival in patients with castrate metastatic disease considered for different hormonal and cytotoxic therapies.

EXPERIMENTAL DESIGN

CTC were isolated by immunomagnetic capture from 7.5-mL samples of blood from 120 patients with progressive clinical castrate metastatic disease. We estimated the probability of survival over time by the Kaplan-Meier method. The concordance probability estimate was used to gauge the discriminatory strength of the informative prognostic factors.

RESULTS

Sixty-nine (57%) patients had five or more CTC whereas 30 (25%) had two cells or less. Higher CTC numbers were observed in patients with bone metastases relative to those with soft tissue disease and in patients who had received prior cytotoxic chemotherapy relative to those who had not. CTC counts were modestly correlated to measurements of tumor burden such as prostate-specific antigen and bone scan index, reflecting the percentage of boney skeleton involved with tumor. Baseline CTC number was strongly associated with survival, without a threshold effect, which increased further when baseline prostate-specific antigen and albumin were included.

CONCLUSIONS

Baseline CTC was predictive of survival, with no threshold effect. The shedding of cells into the circulation represents an intrinsic property of the tumor, distinct from extent of disease, and provides unique information relative to prognosis.

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.

Circulating tumor cells: detection, molecular profiling and future prospects

Disseminated malignancy is responsible for the vast majority of cancer-related deaths. During this process, circulating tumor cells (CTC) are generated, spread from the primary tumor, colonize distant organs and lead to overt metastatic disease. CTC are essential for establishing metastasis; however, they are not sufficient as this process is highly inefficient and most will fail to grow in target sites. Several CTC die during migration while others remain dormant for several years and very few grow into macrometastases. CTC have been well documented in the bloodstream of cancer patients; however, the clinical relevance of this detection is still the subject of controversies and their biology is poorly understood. Indeed, available markers fail to distinguish between subgroups of CTC, and several current methods lack sensitivity, specificity or reproducibility in CTC characterization and detection. The advent of more precise technologies is renewing the interest in CTC biology. We will review herein recent findings on CTC biology, on the role of host-tumor interactions in CTC shedding and implantation, available methods of CTC detection and future perspectives for the molecular characterization of the CTC subset(s) responsible for the development of metastasis. Ultimately, understanding CTC biology and host-tumor 'complementarities' will help define metastasis-related biomarkers providing formidable and tailored novel therapeutic targets.

High detection rate of circulating tumor cells in blood of patients with prostate cancer using telomerase activity

BACKGROUND

Circulating tumor cells (CTCs) cannot be readily detected with currently available methods in the majority of patients with prostate cancer. Telomerase activation, one of the major immortalization events, is found in most cases of prostate cancer. We attempted to develop a method using telomerase activity to isolate CTCs in patients with prostate cancer.

PATIENTS AND METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood using Ficoll-Hypaque. Immunomagnetic beads coated with an epithelial cell-specific antigen antibody (BerEP4) were used to harvest epithelial cells from PBMCs. Telomerase activity was detected in harvested epithelial cells using the telomerase-PCR-enzyme-linked immunosorbent assay method.

RESULTS

Blood samples from 107 patients with prostate cancer were studied. CTCs were detected in 19 of 24 (79%) patients with advanced prostate cancer. In contrast, CTCs were not detected in blood samples from 22 healthy male volunteers. CTCs were even identified in patients with an undetectable (<0.1 ng/ml) serum prostate-specific antigen (PSA). CTCs were detected in 55 of 70 (79%) patients with localized prostate cancer before radical prostatectomy (n = 30) or brachytherapy (n = 40). CTCs were also detected in 3 of 13 patients (23%) with an undetectable serum PSA measured at least 1 year after radical prostatectomy, which is consistent with the expected relapse rate in this setting.

CONCLUSION

CTCs can be detected using telomerase activity in a large majority and a wide variety of patients with prostate cancer, including those with localized disease.

Evaluation and significance of circulating epithelial cells in patients with hormone-refractory prostate cancer

OBJECTIVE

To determine the feasibility of using flow cytometry fluorescence-activated cell sorting (FACS) analysis for detecting circulating epithelial cells (CECs) in patients with hormone-refractory prostate cancer (HRPC), and to determine whether CECs can be used to predict survival in these patients.

PATIENTS AND METHODS

Several prognostic models that include routinely used clinical and laboratory variables for predicting survival in men with HRPC have been reported; the presence of CECs measured by reverse transcriptase-polymerase chain reaction for prostate-specific antigen (PSA) in patients with HRPC is an independent prognostic factor for survival. CECs detected by FACS analysis correlate with advanced stage and poor survival outcome. A retrospective study was conducted to assess the presence of CECs by FACS analysis in metastatic HRPC patients initiating systemic chemotherapy with a taxane-based regimen. The association between clinical variables previously described and the presence of CECs along with the effect of the magnitude of CECs on survival was calculated, in 41 patients with HRPC, all of whom had peripheral blood collected for FACS analysis.

RESULTS

Except for four patients, all those with metastatic HRPC had detectable CECs. Among these patients, the number of CECs/mL was correlated with age, serum PSA level and serum alkaline phosphatase (ALP). Higher serum levels of PSA and ALP predicted a poor survival outcome. Similarly, patients with < or =1.8 CECs/mL had a significantly longer survival than those with more CECs/mL (P = 0.02). With a median follow-up of 15.4 months, the median overall survival for all patients was 18.4 months.

CONCLUSIONS

The presence of more CECs in patients with metastatic HRPC was associated with a poorer survival outcome; levels of > or =1.8 CECs/mL were associated with a shorter survival in patients with metastatic HRPC.

Correlation between CD8+ T cells specific for prostate-specific antigen and level of disease in patients with prostate cancer

Modest work has been performed to improve the sensitivity of residual disease detection or investigate the contribution that the immune system makes in controlling metastatic tumor growth, in particular, the frequency and biological actions of peptide-specific CD8+ T lymphocytes in limiting metastatic disease and/or maintaining remission. Fifty-three peripheral blood samples from 32 prostate cancer (PC) patients were investigated for the presence of circulating prostate-specific antigen (PSA)-expressing cells (CPECs) using a highly sensitive and specific assay combining immunomagnetic epithelial cell enrichment with nested RT-PCR of PSA mRNA. Using HLA-A2 tetramer complexes, frequency of CD8+ T cells specific for PSA-derived peptides was determined. Additionally, serum concentrations of PSA and testosterone were measured. CPECs were detected in 26% of peripheral blood samples from PC patients. CD8+ T cells specific for PSA-derived peptides were detected at low frequency in HLA-A2-positive PC patients. The correlation between these PSA-specific CD8+ T cells and residual prostate tumor cells and clinical measures was investigated. Our data suggest that frequency of PSA-specific CD8+ T cells is correlated to CPECs, but not to serum PSA level.

Activities and accomplishments of the cancer and leukemia group B genitourinary committee

The Cancer and Leukemia Group B Genitourinary (GU) Committee has developed a multidisciplinary approach to treatment of GU cancer and has integrated correlative science research into the major research themes of the GU Committee. In localized prostate cancer, trials have evaluated novel approaches in radiation therapy. For patients with recurrence after local therapy, a trial evaluating local recurrence with salvage prostatectomy and a study of systemic therapy with "peripheral androgen blockade" were undertaken. Major contributions have been made in developing and testing therapeutics for advanced, androgen-independent prostate cancer (ketoconazole, suramin, estramustine/docetaxel, and docetaxel/bevacizumab), and in developing predictive markers and algorithms to assess prognosis in these patients. Contributions in kidney cancer have included the development of novel trial methodology, such as the randomized discontinuation trial design, and the testing of antiangiogenics. In addition to these areas, future work of the committee will include further development of therapy for earlier-stage prostate cancer patients and bladder cancer patients.

Circulating tumor cells: the 'leukemic phase' of solid cancers

It is well known that malignant cells circulate in the bloodstream of patients with solid tumors. However, the biological significance of circulating tumor cells (CTCs) and the clinical relevance of their detection are still debated. Besides technical issues regarding CTC-detection methods, discontinuous shedding of CTCs from established cancer deposits, genomic instability and metastatic inefficiency might underlie the conflicting results currently available. Nevertheless, technological advances and recent clinical findings are prompting researchers to dissect CTC biology further. Here, we review these recent findings, and discuss the prospects for the identification and molecular characterization of the CTC subset that is responsible for metastasis development. This would provide a formidable tool for prognosis evaluation, anticancer-drug development and, ultimately, cancer-therapy personalization.

Circulating tumor cells predict survival in patients with metastatic prostate cancer

OBJECTIVES

To determine whether circulating tumor cells (CTCs) predict for survival in patients with metastatic prostate cancer (PCa) and to compare its prognostic abilities with other clinical factors.

METHODS

Blood samples from 37 patients with metastatic PCa were analyzed for CTCs. CTCs were enriched from 7.5 mL blood using magnetic nanoparticles targeting the epithelial cell adhesion molecule and then fluorescently labeled. The samples were analyzed by multiparameter flow cytometry, and events with appropriate light scatter properties that were nucleic acid dye positive, cytokeratin positive, and CD45 negative were defined as CTCs.

RESULTS

The number of CTCs found ranged from 0 to 8586 per 7.5 mL (mean 530 +/- 1887, median 5). A threshold of 5 or more CTCs per 7.5 mL of blood was used to evaluate the ability of CTCs to predict for overall survival. Of the 37 patients, 23 (62%) had 5 or more CTCs, with a median overall survival of 0.70 year compared with more than 4 years for those patients with fewer than 5 CTCs (log-rank P = 0.002, Cox hazards ratio 7.4). In the subset of 26 patients with hormone-refractory PCa, the presence of CTCs was the most significant parameter predictive of survival in univariate and multivariate analyses.

CONCLUSIONS

In this pilot study, the presence of 5 or more CTCs in 7.5 mL blood was associated with poor overall survival in patients with metastatic PCa.

Prognostic Significance of Baseline Reverse Transcriptase-PCR for Prostate-Specific Antigen in Men with Hormone-Refractory Prostate Cancer Treated with Chemotherapy

PURPOSE

Methods accurately categorizing the diverse biology of prostate cancer are needed. A positive baseline reverse transcriptase-PCR for prostate-specific antigen (RT-PCR PSA) in the androgen-independent setting is an independent prognostic marker of survival. The objectives of the current study were to examine the prognostic implication of baseline RT-PCR PSA positivity during treatment with an active chemotherapeutic agent and explore whether an RT-PCR PSA "response" provides prognostic information.

MATERIALS AND METHODS

In a combined analysis of a phase I and a randomized phase II trial of BMS-247550 (an epothilone B analogue), 104 patients with hormone-refractory prostate cancer had whole blood samples collected at baseline, then with each cycle of therapy. RT-PCR PSA was assessed and related to time to progression (TTP).

RESULTS

From 100 evaluable patients, 368 samples were received, of which 90.8% were evaluable for RT-PCR PSA status. Baseline RT-PCR PSA status was significantly associated with TTP (hazard ratio, 2.22; 95% confidence interval, 1.40-3.52). Twenty-six of 38 patients positive at first assessment had at least one follow-up RT-PCR PSA that was negative ("response"). In univariate analysis, RT-PCR PSA response was not significantly associated with TTP, but in multivariate analysis, RT-PCR PSA response was of borderline statistical significance in predicting TTP (hazard ratio, 0.41; 95% confidence interval, 0.16-1.01).

CONCLUSION

These results provide further confirmation that baseline RT-PCR PSA is a statistically significant predictor of TTP in hormone-refractory prostate cancer. Moreover, this is the first report to suggest that RT-PCR PSA response during chemotherapy treatment may predict TTP.

Detection and isolation of circulating tumor cells in urologic cancers: a review

The American Cancer Society has estimated that in 2003, there will be approximately 239,600 new cases of urologic cancer diagnosed and 54,600 urologic cancer-related deaths in the United States. To date, the majority of research and therapy design have focused on the microenvironment of the primary tumor site, as well as the microenvironment of the metastatic or secondary (target) tumor site. Little attention has been placed on the interactions of the circulating tumor cells and the microenvironment of the circulation (i.e., the third microenvironment). The purpose of this review is to present the methods for the detection and isolation of circulating tumor cells and to discuss the importance of circulating tumor cells in the biology and treatment of urologic cancers.

Preliminary study of immunomagnetic quantification of circulating tumor cells in patients with advanced disease

OBJECTIVES

To enumerate the amount of circulating tumor cells (CTCs) in patients with advanced prostate cancer and to investigate the relationship between these numbers, prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSM) expression, and clinical parameters.

METHODS

Whole blood was collected in proprietary CellSave tubes. Mononuclear cell fractions were isolated using epithelial cell antibody-coated magnetic nanoparticles. On one half of each immunomagnetically enriched cell fraction, automated fluorescent microscopy was used to identify the epithelial tumor cells. From the remainder of each sample, RNA extraction, cDNA synthesis, and polymerase chain reaction amplification of PSA and PSM were performed.

RESULTS

Eighty-four patients with advanced prostate cancer submitted 130 samples for analysis. Intact CTCs were identified in 62% of samples; 83.3% of CTC-positive and 0% of CTC-negative samples were reverse transcriptase-polymerase chain reaction positive for PSA and PSM (P = 0.001). A significant positive correlation was found between the CTC number and PSA (r = 0.49), alkaline phosphatase (r = 0.47), and lactate dehydrogenase (r = 0.55) levels, and a significant negative correlation with hemoglobin (r = -0.35). The initial Gleason grade, prior therapy, current therapy, and type of metastasis (bone, soft tissue) did not correlate significantly with the CTC number.

CONCLUSIONS

The presence of intact CTCs and the expression of PSA and PSM demonstrated robust agreement. The tumor cell numbers reflected current disease status and correlated significantly with the clinical disease indicators of PSA, hemoglobin, and liver function tests. These findings warrant further investigation of the diagnostic and prognostic value of enumerating intact CTCs.

Workshop on Cancer Biometrics: Identifying Biomarkers and Surrogates of Cancer in Patients

The current excitement about molecular targeted therapies has driven much of the recent dialog in cancer diagnosis and treatment. Particularly in the biologic therapy of cancer, identifiable antigenic T-cell targets restricted by MHC molecules and the related novel stress molecules such as MICA/B and Letal allow a degree of precision previously unknown in cancer therapy. We have previously held workshops on immunologic monitoring and angiogenesis monitoring. This workshop was designed to discuss the state of the art in identification of biomarkers and surrogates of tumor in patients with cancer, with particular emphasis on assays within the blood and tumor. We distinguish this from immunologic monitoring in the sense that it is primarily a measure of the tumor burden as opposed to the immune response to it. Recommendations for intensive investigation and targeted funding to enable such strategies were developed in seven areas: genomic analysis; detection of molecular markers in peripheral blood and lymph node by tumor capture and RT-PCR; serum, plasma, and tumor proteomics; immune polymorphisms; high content screening using flow and imaging cytometry; immunohistochemistry and tissue microarrays; and assessment of immune infiltrate and necrosis in tumors. Concrete recommendations for current application and enabling further development in cancer biometrics are summarized. This will allow a more informed, rapid, and accurate assessment of novel cancer therapies.

The Use of Real-Time Reverse Transcription-PCR for Prostate-Specific Antigen mRNA to Discriminate between Blood Samples from Healthy Volunteers and from Patients with Metastatic Prostate Cancer

PURPOSE

A clinical role for nonquantitative reverse transcription-PCR (RT-PCR) using prostate-specific antigen in blood samples from patients with prostate cancer remains undefined. Assay variation and detection of prostate-specific antigen mRNA illegitimate transcription may explain inconsistent results between studies. Defining levels of prostate-specific antigen mRNA expression in blood samples from healthy volunteers and patients with prostate cancer would allow cutoffs to be established to distinguish the two groups.

EXPERIMENTAL DESIGN

Quantitative real-time RT-PCR for prostate-specific antigen mRNA was established and levels of prostate-specific antigen mRNA measured in bloods samples from healthy volunteers (n=21) and patients with localized (n=27) and metastatic (n=40) prostate cancer.

RESULTS

Levels of prostate-specific antigen mRNA were significantly higher in blood samples from patients with metastatic prostate cancer than in blood samples from patients with localized prostate cancer (P <0.001) or in blood samples from healthy volunteers (P <0.01); levels between patients with localized prostate cancer and healthy volunteers were no different. Assay sensitivity to detect patients with metastatic prostate cancer was 68% with specificity of 95%. In patients with newly diagnosed metastatic prostate cancer, monitoring response to hormonal therapy was possible with this assay. No correlation between levels of prostate-specific antigen mRNA and serum prostate-specific antigen protein levels was found, suggesting that prostate-specific antigen mRNA and serum prostate-specific antigen protein levels reflect different features of prostate cancer, i.e., circulating tumor cells and total tumor bulk, respectively.

CONCLUSIONS

Quantitative RT-PCR discriminates patients with metastatic prostate cancer from healthy volunteers and patients with localized prostate cancer but cannot discriminate patients with localized prostate cancer from healthy volunteers. A role for quantitative RT-PCR has been identified in the assessment and monitoring of patients with metastatic prostate cancer.

Multigene Reverse Transcription-PCR Profiling of Circulating Tumor Cells in Hormone-Refractory Prostate Cancer

Background: Circulating tumor cells (CTCs) represent a surrogate source of tissue and conceptually represent a “real-time” biopsy. We previously reported that the number of CTCs mirrors disease progression in hormone-refractory prostate cancer (HRPC). To improve characterization of CTCs we further investigated whether in vitro transcription-based multigene reverse transcription-PCR expression profiles could be obtained from CTCs in HRPC.

Methods: We evaluated the expression of 37 genes with potential utility for epithelial cell characterization from antisense RNA libraries constructed from immunomagnetically enriched CTCs from 7.5-mL blood samples from healthy donors and patients with HRPC.

Results: In the control group 13 of 37 genes were not expressed. The most notable of the genes expressed in CTCs of 23 blood specimens drawn from 9 patients with metastatic prostate cancer were prostate-specific antigen (20 of 23; 87%), prostate-specific membrane antigen (17 of 23; 74%), androgen receptor (16 of 23; 70%), human glandular kallikrein 2 (7 of 23; 30%), epidermal growth factor receptor (4 of 23; 17%), and prostate-specific gene with homology to G protein receptor (2 of 23; 9%). The number of CTCs in these samples ranged from 4 to 283 in 7.5 mL of blood (mean, 87; median, 89). Expression of some of the genes was low in the control samples and higher in the patient samples. In all 23 samples, cytokeratin 19, epithelial cell adhesion molecule, or mucin 1 was expressed. Because of background expression in the controls, expression of 13 of the 37 genes, including HER-2, p53, and BCL-2, could not be measured in CTCs.

Conclusion: Antisense RNA libraries can be constructed from CTCs and gene expression profiles of CTCs obtained from patients with HRPC. This could enhance the characterization of HRPC and facilitate the development of more effective therapies.

Update on hormone-refractory prostate cancer

PURPOSE OF REVIEW

Androgen deprivation therapy is the cornerstone treatment for men with de novo or recurrent metastatic prostate cancer. Unfortunately, androgen deprivation therapy is primarily palliative, with nearly all men progressing to an androgen-independent state. Hormone-refractory prostate cancer presents significant management challenges and is the focus of this review.

RECENT FINDINGS

Investigations into the pathophysiology of hormone-refractory prostate cancer, the exploration of chemotherapeutic combinations, novel biological targets, skeletal protectants, and radiopharmaceuticals, as well as new prognostic tools are expanding the clinician's armamentarium and improving patient outcomes.

SUMMARY

Bisphosphonates and chemotherapy are providing effective palliative approaches. Phase II trials of taxane-based regimens show higher response rates and longer survival than has typically been achieved with existing standards. Two completed randomized phase III studies to be reported in mid-2004 will more definitively answer the question of whether currently available chemotherapy can improve survival.

Use of nomograms for predicting survival in patients with castrate prostate cancer

Given the heterogeneity of prognoses in patients with castrate metastatic prostate cancer, the ability to accurately predict survival is vital for optimal patient counseling, selection of treatments, clinical trial design, and interpretation of clinical data. Over the past 20 years, several prognostic models have been developed in an attempt to refine the clinician's predictive ability. Early models were based on patients with more advanced disease. They included variables that are no longer regularly encountered today and involved cumbersome calculations that were not practical for everyday use in the clinic. Recently, 2 point-based nomograms have been developed based on pretreatment variables measured on a routine basis. These models provide a user-friendly format in which to make sophisticated predictions of survival. These models have improved our ability to predict the outcomes of patients with castrate metastatic disease. However, further work to identify novel prognostic markers to improve the accuracy of these predictions is needed.

Prognostic factors for survival in patients with hormone-refractory prostate cancer (HRPC) after initial androgen deprivation therapy (ADT)

Androgen deprivation therapy (ADT) is a standard mode of therapy for patients with metastatic prostate cancer. Controversy exists, however, as to the optimal timing of initiation of ADT, as well as whether this form of therapy imparts a survival benefit to patients with advanced disease. Side effects of ADT are not minimal and can seriously compromise a patient's quality of life. Additionally, ADT eventually results in hormone-refractory prostate cancer (HRPC). Despite new chemotherapeutic regimens and hormonal agents, overall survival in these patients remains universally low. Nonetheless, it is valuable to gauge a patient's prognosis to assist in decision making when considering treatment options. Contemporary series analyzing patients with HRPC have identified several factors prognostic of survival outcomes, such as lactate dehydrogenase (LDH), alkaline phosphatase (ALK), hemoglobin (Hgb), and serum prostate specific antigen (PSA) level. Nomograms have been developed that utilize these pretreatment clinical variables to predict clinical outcomes, including 1-year, 2-year, and median survival times in patients with HRPC. These instruments are capable of more accurately predicting survival outcomes than traditional tables of multivariate results or simple analysis of prognostic factors. We believe these nomograms will become indispensable tools for patient counseling and clinical trial design in patients with HRPC.

Prognostic model for predicting survival in men with hormone-refractory metastatic prostate cancer

PURPOSE

To develop and validate a model that can be used to predict the overall survival probability among metastatic hormone-refractory prostate cancer patients (HRPC).

PATIENTS AND METHODS

Data from six Cancer and Leukemia Group B protocols that enrolled 1,101 patients with metastatic hormone-refractory adenocarcinoma of the prostate during the study period from 1991 to 2001 were pooled. The proportional hazards model was used to develop a multivariable model on the basis of pretreatment factors and to construct a prognostic model. The area under the receiver operating characteristic curve (ROC) was calculated as a measure of predictive discrimination. Calibration of the model predictions was assessed by comparing the predicted probability with the actual survival probability. An independent data set was used to validate the fitted model.

RESULTS

The final model included the following factors: lactate dehydrogenase, prostate-specific antigen, alkaline phosphatase, Gleason sum, Eastern Cooperative Oncology Group performance status, hemoglobin, and the presence of visceral disease. The area under the ROC curve was 0.68. Patients were classified into one of four risk groups. We observed a good agreement between the observed and predicted survival probabilities for the four risk groups. The observed median survival durations were 7.5 (95% confidence interval [CI], 6.2 to 10.9), 13.4 (95% CI, 9.7 to 26.3), 18.9 (95% CI, 16.2 to 26.3), and 27.2 (95% CI, 21.9 to 42.8) months for the first, second, third, and fourth risk groups, respectively. The corresponding median predicted survival times were 8.8, 13.4, 17.4, and 22.80 for the four risk groups.

CONCLUSION

This model could be used to predict individual survival probabilities and to stratify metastatic HRPC patients in randomized phase III trials.