Prevalent vs Incident PSA Screen-detected Prostate Cancer
Abstract & Commentary
By William B. Ershler, MD
Synopsis: Among patients who undergo screening and are diagnosed with prostate cancer, there is a dichotomy between those who are diagnosed after their initial screening (prevalent cases) and those who have cancer detected after subsequent screenings (incident cases). In the current analysis, "prevalent" cases were found to have a poorer outcome after radical prostatectomy than "incident" cases. This finding may be of clinical value, in conjunction with other prognostic factors, in the estimation of risk of recurrence and determining treatment strategies.
Source: Nguyen PL, et al. Biochemical recurrence after radical prostatectomy for prevalent versus incident cases of prostate cancer: implications for management. Cancer. 2008; 113:3146-3152.
Prostate cancer (PC) screening remains controversial, and whether regular screening can decrease cancer-specific and overall mortality rates remains to be determined. However, it is clear that screening has led to a downward migration in age at diagnosis and lower stage and Gleason scores, all of which are associated with a lower PSA level at the time of diagnosis.1 Among screened populations, it is unknown whether men with PC diagnosed at the initial screening (prevalent cases) have a different outcome than men who are diagnosed at subsequent screenings (incident cases) after adjusting for known prognostic factors. One study indicated that prevalent cases tend to consist of more poorly differentiated and higher volume tumors than incident cases,2 whereas another found that patients who were diagnosed on their initial screening had a higher mean PSA, more advanced clinical tumor (T) classification, and had a greater proportion of high Gleason scores than patients who were diagnosed in subsequent rounds of screening.3
The current study was undertaken to determine if the risk of biochemical recurrence is greater for "prevalent" vs "incident" cases, after adjusting for other prognostic factors. The study cohort was comprised of 1,923 men from a prospective PC screening study who underwent radical prostatectomy (RP) between September 19, 1989 and May 22, 2002. Cox regression multivariate analysis was used to determine whether having prevalent PC vs incident PC was associated with the time-to-failure after RP, after adjusting for PSA level, Gleason score, clinical tumor (T) classification, and year of RP.
As expected, men with prevalent PC had higher PSA levels (p < .001) and more advanced clinical T classification (p < .001) than men with incident PC. After a median follow-up of 6.1 years, factors that were associated with a significantly shorter time to PSA failure after RP were prevalent PC (adjusted hazard ratio [AHR], 1.8; 95% confidence interval [95% CI], 1.3-2.6; p = .0005), baseline PSA (AHR, 1.07; 95%CI, 1.04-1.09; p < .001), Gleason 7 disease (AHR, 2.5; 95% CI, 1.9-3.3; p < .001), Gleason 8-10 disease (AHR, 2.3; 95%CI, 1.5-3.5; p < .001), and the year of RP (AHR, 0.92; 95%CI, 0.86-0.97; p = .003). Men with prevalent PC also had worse outcomes after adjusting for their more advanced pathologic features.
Commentary
The main finding from this study is that after adjusting for PSA, T classification, and Gleason score, having a prevalent case (ie, prostate cancer) meant shorter time to PSA failure after radical prostatectomy. The clinical implication of this finding is that among screened men who are being considered for surgery, whether their cancer is a prevalent or incident case, should be factored into the calculation of their risk of recurrence in addition to the usual clinical features of PSA, T classification, and Gleason score. Whether prevalent cases would benefit from a more aggressive treatment regimen remains speculative at this time, but could be explored in future trials. Detected as a result of an elevated PSA at the first screening determination (ie, prevalent case) rather than an incident case was significantly associated with known prognostic factors, men with prevalent PC had a poorer outcome after RP than men with incident PC. Nguyen et al believe that this finding should be taken into consideration when weighing the risk of recurrence and treatment options for men who are diagnosed with PC on their initial screening.
These results and conclusions do not fully address the fundamental issue at the heart of the screening controversy. Although the finding that diagnosis after serial screening was associated with a lower recurrence rate than diagnosis after initial screening, is consistent with the hypothesis that earlier and more widespread screening could improve overall outcomes, there is the issue of lead-time bias that tends to inflate the apparent survival of screened patients. Thus, the benefits of screening would best be demonstrated by a randomized trial, two of which are currently underway (one in North America and one in Europe).
References
1. Hugosson J, et al. Results of a randomized, population-based study of biennial screening using serum prostate-specific antigen measurement to detect prostate carcinoma. Cancer. 2004;100:1397-1405.
2. Catalona WJ, et al. Detection of organ-confined prostate cancer is increased through prostate-specific antigen-based screening. JAMA. 1993;270:948-954.
3. van der Cruijsen-Koeter IW, et al. Tumor characteristics and prognostic factors in two subsequent screening rounds with four-year interval within prostate cancer screening trial, ERSPC Rotterdam. Urology. 2006;68:615-620.
Among patients who undergo screening and are diagnosed with prostate cancer, there is a dichotomy between those who are diagnosed after their initial screening (prevalent cases) and those who have cancer detected after subsequent screenings (incident cases).You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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