Unusually large numbers needed to treat for radical prostatectomy in prostate cancer patients with PSA velocity ≤2 ng/ml/year.

BACKGROUND

The numbers needed to treat (NNT) and the corresponding confidence intervals for patients with prostate cancer and defined annual PSA increases (PSA velocity, PSAV) have not been described previously.

AIM

The objective of this study is to assess NNT, numbers needed to treat to harm and corresponding confidence intervals for radical prostatectomy (RP) in patients with prostate cancer defined as a PSAV ≤2 ng/ml/year.

METHODS

NNT following RP were estimated in risk groups defined by PSAV using mortality statistics and hazard ratios obtained in a noncontrolled trial. As no suited control group and no appropriate randomized trials were available for doing this calculation and as such trials are unlikely to become available in the near future we have calculated our NNTs as published previously by using relative risk reduction from an earlier randomized trial (RCT) comparing RP with watchful waiting (WW) [Can J Urol 2006;13(suppl 1):48-55].

RESULTS

For preoperative PSAV >2 ng/ml/year, NNT for RP were estimated at 25, whereas for preoperative PSAV ≤2 ng/ml/year, the estimate was 618. The lower 95% confidence limits (NNTBl) were 9 and 126, respectively (treatment with benefit). The implications emerging from these findings are discussed by comparison with published NNT values from other RCTs. The lower 95% confidence limit for preoperative PSAV ≤2 ng/ml/year was found to be large in comparison.

CONCLUSION

The NNT estimate obtained here for PSAV >2 ng/ml/year and its lower 95% confidence interval is comparable to values in other studies on prostate cancer for therapies considered to be effective, while the estimated NNT for patients with PSAV ≤2 ng/ml/year is large in comparison. We conclude that the benefits of RP for localized prostate cancer with preoperative PSAV ≤2 ng/ml/year may be considered small. There are several limitations to our findings, the most important of which lies in the fact that while PSAV remains significantly associated with outcomes, the predictive value of PSA measurements is low. While PSAV >2 ng/ml/year clearly indicates a need for surgery, a PSAV ≤2 ng/ml/year should imply further decision making.