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Originally published as JCO Early Release 10.1200/JCO.2008.21.5392 on February 23 2009 © 2009 American Society of Clinical Oncology.
Mathematical Rigor Is Necessary, But for Men With Prostate Cancer, Clinical Relevance Is the PriorityHarvard Radiation Oncology Program, Brigham & Women's Hospital, Boston, MA
Department of Statistics, University of Connecticut, Storrs, CT
Department of Radiation Oncology, Brigham & Women's Hospital/Dana-Farber Cancer Institute, Boston, MA To the Editor: We would like to thank Vickers et al1 for their review of 87 of the 1,882 studies published evaluating prostate-specific antigen (PSA) kinetics in the setting of detection of prostate cancer (PC) as well as prognosis in men with known PC. Their goal was to assess whether PSA velocity or doubling time provided additional clinical information for decision making beyond that of absolute PSA level. On the basis of their analysis, the authors assert that there is "little evidence that pretreatment PSA velocity or PSA doubling time are of value for early-stage prostate cancer. There is therefore no justification for the use of PSA dynamics in the clinical setting or as an inclusion criterion for clinical trials in this population."1 The main point that the authors use to justify this conclusion is that they could only find a single study2 comparing the predictive accuracy of a model including both absolute PSA level and a PSA dynamic parameter in addition to established predictors with that including only absolute PSA level and established predictors. We would like to respectfully point out that in clinical practice and when designing patient selection for clinical trials, physicians use risk-based assessment tools3,4 to determine which therapeutic interventions to administer or study, respectively. To that end, studies5–7 that can identify men who have a high risk of PC death on the basis of the value of a PSA dynamic parameter, despite being categorized as low or intermediate risk by absolute PSA level and other established prognostic factors, are clinically useful. This review took the approach in 28 of the 87 papers of hoping to ask the mathematical question for men in a given study of whether a PSA dynamic parameter adds to absolute PSA level in the prediction of outcomes such as recurrence, metastasis, or death, rather than asking the clinically relevant question of whether or not we can use a PSA dynamic parameter to successfully identify that subset of men among those traditionally classified as low or intermediate risk on the basis of absolute PSA level and other established prognostic factors who are really at high risk for recurrence and death. Another point of consideration regarding the review is that studies on detection and prognosis were combined. The potential utility of PSA dynamic constructs in men with a diagnosis of PC as opposed to the general population where benign causes can spuriously elevate PSA (ie, prostatitis, instrumentation, sexual activity, bicycle or horseback riding) can differ, and therefore we respectfully suggest that these states be considered separately. We do agree with recommending continued study of PSA dynamic parameters as well as other novel PC specific parameters to help us reach the goal of identifying those men for biopsy who have clinically significant PC, and once diagnosed, identifying which men require more aggressive as compared with less aggressive treatments to optimize their cancer outcomes. Only with such efforts can we ultimately realize the full potential of personalized medicine for all men at risk for, as well as those who have been diagnosed with, PC. AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST The author(s) indicated no potential conflicts of interest. REFERENCES
1. Vickers AJ, Savage C, O'Brien MF, et al: Systematic review of pretreatment prostate-specific antigen velocity and doubling time as predictors for prostate cancer. J Clin Oncol 27:398–403, 2009. 2. Loeb S, Roehl KA, Catalona WJ, et al: Prostate specific antigen velocity threshold for predicting prostate cancer in young men. J Urol 177:899–902, 2007.[CrossRef][Medline] 3. D'Amico AV, Whittington R, Malkowicz SB, et al: Biochemical outcome after radical prostatectomy, external beam radiation therapy, or interstitial radiation therapy for clinically localized prostate cancer. JAMA 280:969–974, 1998. 4. Stephenson AJ, Scardino PT, Eastham JA, et al: Preoperative nomogram predicting the 10-year probability of prostate cancer recurrence after radical prostatectomy. J Natl Cancer Inst 98:715–717, 2006. 5. D'Amico AV, Renshaw AA, Sussman B, et al: Pretreatment PSA velocity and risk of death from prostate cancer following external beam radiation therapy. JAMA 294:440–447, 2005. 6. D'Amico AV, Hui-Chen M, Renshaw AA, et al: Identifying men diagnosed with clinically localized prostate cancer who are at high risk for death from prostate cancer. J Urol 176:S11–S15, 2006.[CrossRef][Medline] 7. D'Amico AV, Chen MH, Catalona WJ, et al: Prostate cancer-specific mortality after radical prostatectomy or external beam radiation therapy in men with 1 or more high-risk factors. Cancer 110:56–61, 2007.[CrossRef][Medline]
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Copyright © 2009 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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