Preoperative nomogram predicting the 10-year probability of prostate cancer recurrence after radical prostatectomy

Abstract

An existing preoperative nomogram predicts the probability of prostate cancer recurrence, defined by prostate-specific antigen (PSA), at 5 years after radical prostatectomy based on clinical stage, serum PSA, and biopsy Gleason grade. In an updated and enhanced nomogram, we have extended the predictions to 10 years, added the prognostic information of systematic biopsy results, and enabled the predictions to be adjusted for the year of surgery. Cox regression analysis was used to model the clinical information for 1978 patients treated by two high-volume surgeons from our institution. The nomogram was externally validated on an independent cohort of 1545 patients with a concordance index of 0.79 and was well calibrated with respect to observed outcome. The inclusion of the number of positive and negative biopsy cores enhanced the predictive accuracy of the model. Thus, a new preoperative nomogram provides robust predictions of prostate cancer recurrence up to 10 years after radical prostatectomy.

Fig. 1

A) Preoperative nomogram estimating the 1- to 10-year progression-free probability after radical prostatectomy alone. B) Calibration plot of the nomogram in external validation. The 45° line represents an ideal model in which estimates of recurrence are perfectly calibrated with outcome. Vertical bars are 95% confidence intervals for quintiles in the validation set. Instructions for physician: Locate patient's preoperative prostate-specific antigen (PSA) on the Preoperative PSA axis. Draw a straight line down to the Points axis to determine how many points toward disease recurrence that patient receives. Repeat this process for each of the remaining variable axes. Sum the points for each predictor and locate this sum on the Total Points axis. Draw a line straight up from the Total Points axis until it intersects with the horizontal line drawn from Months from Surgery, corresponding to the time point in the future within which the risk of recurrence is wished to be calculated. The progression-free probability can be estimated at 12 to 120 months after radical prostatectomy. The slanted vertical line that crosses this intersection point corresponds to the calculated progression-free probability within that point in time after radical prostatectomy. Instructions for patient: Mr. X, if we had 100 men exactly like you, we would predict <predicted probability from nomogram×100> percent to remain free of disease progression at <specified months from surgery> following radical prostatectomy alone.