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© The Author 2007. Published by Oxford University Press.
CORRESPONDENCE |
Response: Re: Detection of Life-Threatening Prostate Cancer With Prostate-Specific Antigen Velocity During a Window of Curability
Affiliations of authors: James Buchanan Brady Urological Institute (HBC, PL, JW, BJT) and Department of Pathology (JIE), Johns Hopkins School of Medicine, Baltimore, MD; National Institute on Aging, NIA-ASTRA Harbor Hospital, Baltimore, MD (LF, AK, EJM)
Correspondence to: H. Ballentine Carter, MD, James Buchanan Brady Urological Institute, Johns Hopkins School of Medicine, 600 North Wolfe St, Marburg Building, Rm 145, Baltimore, MD 21287 (e-mail: hcarter{at}jhmi.edu).
Our recommendation that prostate-specific antigen velocity (PSAV) be part of a decision algorithm for prostate biopsy referral is based on observations that include a current approach to prostate-specific antigen testing that has resulted in the serendipitous discovery of many cancers that otherwise would have remained undetected (1). The standard approach to biopsy referral based on an absolute PSA threshold has resulted in no treatment benefit for the majority of those men who are diagnosed with prostate cancer today. A recent population-based study (2) reveals that 200 older men with low to intermediate risk prostate cancer (>80% of prostate cancers detected today) need to be treated to prevent one prostate cancer death for 12 years. We predict that in the United States we will soon be labeling one in five men over a lifetime with prostate cancer if the trend of lowering PSA thresholds for biopsy referral and increasing the amount of tissue removed at biopsy continue (3). Thus, we need an alternative approach for biopsy referral that more effectively targets life-threatening disease.
We demonstrated that PSAV 10–15 years before diagnosis was associated with prostate cancer death 1–3 decades later. Because of our limited sample, we did not recommend a specific PSAV threshold for clinical decision, in contrast to the assertion of Etzioni et al. (4), but instead focused on how PSAV could inform decisions regardless of the current PSA measurement. Etzioni et al. argue that because PSA and PSAV are closely related, PSAV provides no incremental value for detection of prostate cancer based on comparisons of sensitivity and specificity. However, PSA and PSAV were not highly correlated (r = .29) when we restricted our dataset to include only PSA levels less than 4.0 ng/mL at 10–15 years before diagnosis. Furthermore, using this restricted dataset at 10–15 years before diagnosis, PSA was not a statistically significant variable (P = .26) in a proportional hazards model that included age, date of diagnosis, and PSA as continuous variables. The addition of PSAV to this model statistically significantly improved the fit of the model based on the likelihood ratio test (P = .03). The area under the receiver operating characteristics curve for PSA and PSAV (after adjusting for age and date of diagnosis) at 10–15 years before diagnosis when PSA levels were less than 4.0 ng/mL was 0.467 (95% confidence interval [CI] = 0.219 to 0.714) and 0.649 (95% CI = 0.405 to 0.894). It is of no surprise to us that data from the Prostate Cancer Prevention Trial (5) show no strong correlation between PSAV and any prostate cancer because it is likely that many men in this trial were diagnosed with indolent disease.
In our opinion, the added value of PSAV derives from the fact that the window of opportunity for detection of curable disease is large—especially among men with PSA values in the range of 2.0–2.5 ng/mL (6)—and that PSAV may allow detection of life-threatening disease at a point when the PSA level is below most clinical decision thresholds. If an asymptomatic man with a normal digital rectal examination and a PSA level of 2.0 ng/mL has a persistent PSAV of 0.4 ng/mL per year, it is likely that he will have curable disease 3–4 years later if he underwent a biopsy at that point based on PSAV. Thus, all men who reach a PSA threshold of 2.0 ng/mL could be subjected to prostate biopsy to avoid exceeding a 20% likelihood that any prostate cancer exists, as suggested by Thompson et al. (5). Alternatively, changes in PSA levels could be monitored, biopsy and the high risk of serendipitous detection of a cancer for which treatment will confer no benefit avoi ded, and life-threatening disease could still be detected at a point when cure is likely among those men whose PSA levels do accelerate. In a randomized screening trial, 50% of men with PSA levels of 2.0–2.9 ng/mL will have PSA levels less than 3.0 ng/mL 4 years later (7). Thus, tracking PSA history and performing a prostate biopsy on those men with a PSAV that suggests the presence of life-threatening disease seems to us to be a worthwhile trade-off to biopsy referral of all men based on a given PSA threshold.
REFERENCES
(1) Etzioni R, Penson DF, Legler JM, di Tommaso D, Boer R, Gann PH, et al. (2002) Overdiagnosis due to prostate-specific antigen screening: lessons from U.S. prostate cancer incidence trends. J Natl Cancer Inst 94:981–90.
(2) Wong Y-N, Mitra N, Hudes G, Localio R, Schwartz JS, Wan F, et al. (2006) Survival associated with treatment vs observation of localized prostate cancer in elderly men. JAMA 296:2683–93.
(3) National Cancer Institute. Surveillance, Epidemiology, and End Results. Available at: http://seer.cancer.gov/statfacts/html/prost.html. [Last accessed: December 21, 2006.].
(4) Etzioni R, Ankerst DP, Thompson IM. (2007) Re: Detection of life-threatening prostate cancer with prostate-specific antigen velocity during a window of curability. J Natl Cancer Inst 99:489.
(5) Thompson IM, Ankerst DP, Chi C, Goodman PJ, Tangen CM, Lucia MS, et al. (2006) Assessing prostate cancer risk: results from the Prostate Cancer Prevention Trial. J Natl Cancer Inst 98:529–34.
(6) van der Cruijsen-Koeter IW, van der Kwast TH, Schroder FH. (2003) Interval carcinomas in the European Randomized Study of Screening for Prostate Cancer (ERSPC)-Rotterdam. J Natl Cancer Inst 95:1462–6.
(7) Schroder R, Raaijmakers R, Postma T, van der Kwast, Roobol M. (2005) 4-year prostate specific antigen progression and diagnosis of prostate cancer in the European randomized study of screening for prostate cancer, section Rotterdam. J Urol 174:489–94.[CrossRef][Web of Science][Medline]
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J Natl Cancer Inst 2007 99: 489-490.
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  R. D. Etzioni, D. P. Ankerst, N. S. Weiss, L. Y. T. Inoue, and I. M. Thompson Is Prostate-Specific Antigen Velocity Useful in Early Detection of Prostate Cancer? A Critical Appraisal of the Evidence J Natl Cancer Inst, October 17, 2007; 99(20): 1510 - 1515. [Abstract] [Full Text] [PDF]
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