
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Cancer Therapy: Clinical |
Authors' Affiliations: 1 Duke Comprehensive Cancer Center, Durham, North Carolina; 2 Sidney Kimmel Comprehensive Cancer Center, Baltimore, Maryland; 3 Department of Medical Oncology, Rotterdam Cancer Institute, Erasmus University Medical Center, Rotterdam, the Netherlands; and 4 Department of Medical Oncology, Princess Margaret Hospital and University of Toronto, Toronto, Ontario, Canada
Requests for reprints: Andrew J. Armstrong, Duke Comprehensive Cancer Center, 2424 Erwin Road, Hock Plaza, Suite 606, Room 6127, Durham, NC 27705. Phone: 919-668-8797; Fax: 919-668-7117; E-mail: andrew.armstrong{at}duke.edu.
| Abstract |
|---|
|
|
|---|
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
2 sites; P = 0.001), (c) clinically significant pain (HR, 1.48; P < 0.0001), (d) Karnofsky performance status (HR, 1.39 if
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.
Baseline PSA kinetics [PSA doubling time (PSADT) or PSA velocity] have not been shown conclusively to be an independent prognostic factor in HRPC, with most analyses based on retrospective reviews of relatively small numbers of patients (6–9). These analyses were limited by the number of controllable covariates, the duration of follow-up, potential confounders, and measurement bias. Furthermore, past prognostic analyses are limited by the inclusion of various types of noncytotoxic therapy and did not include patients treated with docetaxel-based therapy (3, 4).
In 2004, docetaxel was approved for the treatment of men with metastatic HRPC based on large multicenter randomized clinical trials (1, 2). The TAX327 study randomized 1,006 patients to receive one of two schedules of docetaxel or mitoxantrone, each given with low-dose prednisone, and showed an extension of overall survival, improvement in quality of life, pain control, PSA decline, and objective tumor response (2). A second phase III study using estramustine phosphate in combination with docetaxel confirmed the survival advantage of docetaxel-based chemotherapy (1).
The aim of the current analysis is to develop a multivariate prognostic model, based on the TAX327 trial, to investigate the independent prognostic significance of novel prognostic variables, such as pretreatment PSA kinetics, the presence of pain, number of metastatic sites, and the type of disease progression at baseline, in addition to traditional prognostic markers.
| Materials and Methods |
|---|
|
|
|---|
In a subset of 686 men, three or more consecutive baseline PSA measurements each separated by at least 1 week were available for our prognostic evaluation of PSA kinetics. PSA velocity was calculated assuming first-order kinetics as the rise in serum PSA (ng/mL) over time based on individual linear regression before study initiation. PSADT was calculated from these data. PSADT was entered into the model using both continuous and log-transformed variables as well as categorical variables separated by median values.
The main end point of this analysis was duration of survival as defined by the time from randomization to death, with the survival data updated as of November 2006. Patients who were alive as of the cutoff date were administratively censored, whereas patients lost to follow-up were censored. The Kaplan-Meier product limit estimator was used to estimate the survival distribution (10). Univariate and multivariate Cox proportional hazards modeling was done using Stata 8.2 software (StataCorp LP). Cox proportional hazards assumptions were tested using Schoenfeld residual analysis for univariate and multivariate analysis using as a level of significance of 0.01. Comparisons of baseline characteristics were done using 95% confidence intervals (95% CI), t tests, and exploratory statistical analysis. Covariates of interest for univariate analysis included age, performance status, pain at baseline, baseline levels of hemoglobin, alkaline phosphatase and PSA, presence of visceral and/or liver metastases, pretreatment PSADT, type of progression (measurable, nonmeasurable, bone scan, and PSA-only progression), number of metastatic sites, Gleason score, presence of multiple bony metastases, and prior estramustine or second-line hormonal therapy. Variables (other than PSADT) were prospectively collected on case report forms. Tests for interaction were done for baseline PSA and PSADT. Colinearity and normality of variables were evaluated before inclusion. All variables with skewed distributions (PSA and alkaline phosphatase) were log transformed before incorporation. Internal validation of the model was done using the concordance index and internal bootstrap resampling methods, respectively.
In this data set, high-grade tumors were defined by a primary Gleason sum of
8 or a WHO grade of 3 to 4 for those tumors who did not have Gleason sums. This combined variable was included due to the omission of Gleason scoring in 288 subjects (28.6%) and the similarities in morphology in Gleason 8 to 10 compared with WHO 3 to 4.5 The similarities in the point estimates for overall survival on univariate analysis for each of these categories compared with the joint category further validate this assumption. Multiple sites of involvement on bone scan were defined as the presence of more than two regions of nuclear tracer uptake, such as spine and ribs or long bones and pelvis. Performance status was graded using the Karnofsky scale. Pain intensity at baseline was evaluated by the present pain intensity score from the McGill-Melzack questionnaire, and an analgesic score was calculated as the mean daily intake of analgesics, with a score of 4 assigned to a standard dose of narcotic (e.g., 10 mg morphine) and a score of 1 for a standard dose of anon-narcotic (e.g., acetylsalicylic acid or 325 mg acetaminophen; ref. 11). A present pain intensity of
2 and/or an analgesic score of
10 were defined in the original protocol as indicative of the presence of significant pain (2, 11).
The assumptions of the Cox model for our analysis was tested in two ways using binary versions of PSADT alone and also using PSADT and median baseline PSA. In both cases, there was not strong evidence of violation of the proportional hazards assumption based on graphical displays or by using P values (P = 0.07 and 0.04, respectively), and thus, this model design was appropriate for the current analysis.
A stepwise procedure including a bootstrap was used for determining the final model for the nomogram. All variables that were significant in univariate analyses based on an
level of 0.10 were included in a Cox multiple regression model. The covariate with the largest P value was removed, and the model was refit iteratively until all covariates in the model had P values of <0.10. This model was considered the final model for the data set. To prevent against overfitting, this procedure was repeated 500 times using bootstrapped data sets. Covariates that were included in more than half of the final models in the 500 bootstrapped samples were used to define the final set of covariates. The final set of covariates was included in a Cox regression using the original data set. This final Cox proportional hazards regression model was used to create a nomogram for prediction of median and 1-, 2-, and 5-year overall survival, and our approach for development of the nomogram and validation was similar to that described by Kattan et al. (12). The R Design library was used to produce the nomogram and to estimate the c-indices for validation (13, 14). The concordance index is the probability that given two randomly drawn patients that the patient who dies first has the higher predicted mortality based on the model. A higher concordance index on a 0 to 1 scale indicates a higher predictive ability.
| Results |
|---|
|
|
|---|
The median baseline PSADT in this cohort of men was 55.8 days (mean, 79 days; range, 5-1245 days; SD, 92 days). As a secondary analysis, men with a more rapid PSADT (<55 days) were more likely to have pain at baseline, progression on bone scan, multiple hotspots on the baseline bone scan, a lower baseline hemoglobin, and higher baseline alkaline phosphatase compared with those men with a slower PSADT (
55 days; Table 1
).
|
|
55 days) was associated with a 46% increase in the risk of death (HR, 1.46; 95% CI, 1.24-1.73; P < 0.001). Other variables with prognostic significance included extent of involvement on bone scan (more than two regions involved) and type of progression at baseline. Progression by measurable disease or by bone scan was associated with a 26% to 36% increase in the risk of death (HR, 1.26 and 1.36, respectively; P = 0.003 and P < 0.001, respectively), whereas a PSA-only progression at baseline was associated with a 25% decrease in the risk of death (HR, 0.75; 95% CI, 0.61-0.92; P = 0.003). Non-Caucasian race was not significantly associated with better survival but this was based on only 70 non-Caucasian subjects (HR, 0.80; P = 0.13).
In multivariate Cox proportional hazards analysis, 635 men were available for analysis after exclusion of missing data from tumor grade and PSADT. Table 3
describes the relative hazards for each covariate in the final multivariate model. Supplementary Table S3 shows the results of the stepwise model fitting for the 500 boostrapped samples. Independent prognostic factors in order of importance included liver metastases (HR, 1.66; P = 0.019), more than two regions of metastatic disease (HR, 1.63; P = 0.001), chemotherapy type (weekly docetaxel versus q3w docetaxel: HR, 1.12; P = 0.32; mitoxantrone versus q3w docetaxel: HR, 1.43; P = 0.001), significant baseline pain (HR, 1.48; P < 0.001), Karnofsky performance status
70 (HR, 1.39; P = 0.016), bone scan progression (HR, 1.29; P = 0.010) or measurable disease progression (HR, 1.37; P = 0.005), PSADT
55 days (HR, 1.19; P = 0.066), PSA (per log rise, HR, 1.17; P < 0.001), high tumor grade (HR, 1.18; P = 0.069), alkaline phosphatase (per unit log rise, HR, 1.27; P < 0.001), and baseline hemoglobin (per unit decline, HR, 1.11; P = 0.004). In this analysis, each progression category was compared with a reference group without the corresponding progression type (i.e., measurable disease progression compared with no measurable disease progression). Due to colinearity with the presence of liver metastasis at baseline and a weaker prognostic ability, visceral metastasis was dropped from the multivariate model. Additional factors that were not included due to lack of a statistically significant prognostic effect included race, age, number of hotspots on bone scan, prior estramustine, nonmeasurable disease progression, prior radiotherapy, prior surgery, and baseline testosterone (data not shown).
|
|
|
|
| Discussion |
|---|
|
|
|---|
We found baseline PSADT to be independently associated with overall survival, regardless of baseline PSA. We also found that patients with relatively fast PSA kinetics (PSADT <55 days) were more likely to have pain at baseline, higher serum PSA and alkaline phosphatase, lower hemoglobin concentration, more hotspots on the baseline bone scan, and be of younger age. Despite these confounding associations, PSADT retained independent prognostic significance in our multivariate model, and a nomogram was developed that incorporates PSA kinetics along with other significant prognostic variables.
Our study was based on a large phase III trial of men with progressive metastatic HRPC, but PSA kinetics were not calculated nor stratified for nor considered in the primary analysis. Our analysis is thus retrospective and based on a subset of these individuals who had sufficient baseline data to allow an estimation of PSADT and included only men with three or more PSA values separated by more than 1 week. Given the short PSADTs in this cohort of patients with a median of 55 days, this separation of measurements in time seems reasonable. We found that this subgroup of patients with sufficient data on PSA kinetics had a similar median survival to those excluded from the nomogram development and thus should not limit the generalizability of this analysis. These modest differences should not influence the generalization or significance of our findings, and external validation of this model using prospective data sets that capture PSA kinetics is planned.
PSADT has emerged as an easily obtainable and clinically relevant prognostic marker in several stages of prostate cancer, including pre-prostatectomy, pre-radiation therapy, rising PSA after local therapy, nonmetastatic HRPC, and, most recently, metastatic HRPC (6–9, 20–24). After primary therapy, observations across different studies suggest that the PSADT may shorten as the disease progresses, although longitudinal studies are needed to address PSA acceleration within the same groups of patients. Despite this shortening in median doubling time in metastatic HRPC, heterogeneity still exists in overall survival, as indicated by our multivariate model and nomogram.
In addition to PSA and PSADT, we identified several important prognostic markers from our data set, including number of metastatic sites (three or more), type of chemotherapy, presence of pain, presence of liver metastases, and type of progression at baseline (measurable disease or bone scan compared with PSA only). Baseline pain and pain response have been evaluated as prognostic markers in numerous data sets and should be considered a validated prognostic factors based on this and prior analyses (16, 25–28). Liver metastases were found to carry greater influence than overall visceral metastases: they may be more common with neuroendocrine differentiation, which may itself have prognostic import 7(16, 28–30). An additional novel independent factor in this analysis was the mode of disease progression at baseline, wherein men who had progression by bone scan or measurable soft tissue disease had a 1.28- and 1.40-fold increased risk of death, respectively, compared with those men without these modes of progression, such as PSA-only or nonmeasurable disease progression (P = 0.014 and 0.002, respectively).
The nomogram and multivariate model was found to have a bootstrap concordance index of 0.69, indicating that, for 31% of patient pairs, the patient predicted to have a better prognosis died first. This predictive ability compares favorably with the concordance indices (0.67-0.68) seen with prior nomograms that have not been validated in the current era of docetaxel-based chemotherapy (3, 4, 31). Prior nomograms have not included patient symptoms, such as pain, nor have they examined the independent role of disease burden or PSA kinetics. The lack of complete predictive ability illustrates that, despite the inclusion of 10 independently significant variables, additional factors may contribute to overall survival. Other potential factors that were not examined in this model include lactate dehydrogenase, albumin, serum biomarkers for vascular endothelial growth factor and other cytokines, circulating tumor cells, type of treatment beyond progression, and other unmeasured prognostic factors (3, 4, 32–37). The addition of these biomarkers in future studies may increase the predictive ability of this nomogram, whereas the addition of PSA kinetics, pain, mode of progression, and number of sites of metastases may add predictive ability to other nomograms that did not contain these variables.
In conclusion, we have developed a baseline prognostic model and nomogram for men with HRPC using the largest clinical trial data set available for this disease. This model shows internal validity to a similar degree compared with historic models in the pre-docetaxel era and includes simple and easily obtainable clinical variables that may be useful for clinical prognostication or stratification of subjects in clinical trials in this population. In addition, we have shown that PSADT, baseline pain, mode of progression, and the number of metastatic disease sites are independently associated with risk of death in men with HRPC, despite accounting for traditional risk factors. Prospective external validation of this model is planned and will be essential for more widespread clinical application.
| Acknowledgments |
|---|
| Footnotes |
|---|
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Note: Supplementary data for this article are available at Clinical Cancer Research Online (http://clincancerres.aacrjournals.org/).
M. Eisenberger is a consultant to Sanofi-Aventis, Celgene, Cytogen, Bristol-Myers Squibb, Merck, and ImClone. R. de Wit is a consultant to Sanofi-Aventis.
5 I. Sesterhenn, personal communication. ![]()
Received 5/ 1/07; revised 7/17/07; accepted 8/ 2/07.
| References |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
S. Halabi, N. J. Vogelzang, S.-S. Ou, K. Owzar, L. Archer, and E. J. Small Progression-Free Survival as a Predictor of Overall Survival in Men With Castrate-Resistant Prostate Cancer J. Clin. Oncol., June 10, 2009; 27(17): 2766 - 2771. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. Festuccia, G. L. Gravina, A. M. D'Alessandro, P. Muzi, D. Millimaggi, V. Dolo, E. Ricevuto, C. Vicentini, and M. Bologna Azacitidine improves antitumor effects of docetaxel and cisplatin in aggressive prostate cancer models Endocr. Relat. Cancer, June 1, 2009; 16(2): 401 - 413. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. J. Armstrong, P. Creel, J. Turnbull, C. Moore, T. A. Jaffe, S. Haley, W. Petros, S. Yenser, J. P. Gockerman, D. Sleep, et al. A Phase I-II Study of Docetaxel and Atrasentan in Men with Castration-Resistant Metastatic Prostate Cancer Clin. Cancer Res., October 1, 2008; 14(19): 6270 - 6276. [Abstract] [Full Text] [PDF] |
||||
![]() |
G. Sonpavde, M. T. Fleming, T. E. Hutson, and M. D. Galsky Trial Design for Metastatic Castration-Resistant Prostate Cancer J. Clin. Oncol., July 20, 2008; 26(21): 3647 - 3648. [Full Text] [PDF] |
||||
![]() |
H. I. Scher, S. Halabi, I. F. Tannock, M. Morris, C. N. Sternberg, M. A. Carducci, M. A. Eisenberger, C. Higano, G. J. Bubley, R. Dreicer, et al. In Reply J. Clin. Oncol., July 20, 2008; 26(21): 3648 - 3649. [Full Text] [PDF] |
||||
![]() |
S. Halabi, N. J. Vogelzang, A. B. Kornblith, S.-S. Ou, P. W. Kantoff, N. A. Dawson, and E. J. Small Pain Predicts Overall Survival in Men With Metastatic Castration-Refractory Prostate Cancer J. Clin. Oncol., May 20, 2008; 26(15): 2544 - 2549. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. Nabhan Is Chemotherapy the Standard for Asymptomatic Androgen-Independent Prostate Cancer? J. Clin. Oncol., May 10, 2008; 26(14): 2413 - 2414. [Full Text] [PDF] |
||||
![]() |
A. J. Armstrong, E. L. Garrett-Mayer, and M. Eisenberger Re: Adaptive Therapy for Androgen-Independent Prostate Cancer: A Randomized Selection Trial of Four Regimens J Natl Cancer Inst, May 7, 2008; 100(9): 681 - 682. [Full Text] [PDF] |
||||
![]() |
R. E. Millikan, C. J. Logothetis, and P. F. Thall Response:Re: Adaptive Therapy for Androgen-Independent Prostate Cancer: A Randomized Selection Trial of Four Regimens J Natl Cancer Inst, May 7, 2008; 100(9): 682 - 683. [Full Text] [PDF] |
||||
![]() |
H. I. Scher, S. Halabi, I. Tannock, M. Morris, C. N. Sternberg, M. A. Carducci, M. A. Eisenberger, C. Higano, G. J. Bubley, R. Dreicer, et al. Design and End Points of Clinical Trials for Patients With Progressive Prostate Cancer and Castrate Levels of Testosterone: Recommendations of the Prostate Cancer Clinical Trials Working Group J. Clin. Oncol., March 1, 2008; 26(7): 1148 - 1159. [Abstract] [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Cancer Research | Clinical Cancer Research |
| Cancer Epidemiology Biomarkers & Prevention | Molecular Cancer Therapeutics |
| Molecular Cancer Research | Cancer Prevention Research |
| Cancer Prevention Journals Portal | Cancer Reviews Online |
| Annual Meeting Education Book | Meeting Abstracts Online |