Nomogram predicting treatment-related bowel dysfunction for men with localized prostate cancer treated by radical prostatectomy (RP), external-beam radiotherapy (EBRT), and brachytherapy (PI).
55 Background: RP, EBRT, and PI for treatment of clinically localized prostate cancer may negatively impact bowel function. Predictions of treatment-related bowel problems from patient-reported, prospective data may be useful in treatment decision-making. Methods: Patient-reported data on treatment-related bowel problems was obtained from 4 prospective, longitudinal, health-related quality-of-life (HRQOL) protocols comprising 2,668 patients treated between 1999 and 2011 by RP (n=1294), EBRT (n=630), and PI (n=744). A single HRQOL instrument was not uniformly used for each study, though all patients were asked if they experienced bother related to bowel problems using a similar 5-point scale. Patient responses were obtained at baseline and at 2 years after treatment. The endpoint of the model was bowel dysfunction, defined as bowel symptoms that were identified as a moderate-to-big problem. Cox proportional hazards regression analysis was used to model the clinical information and follow-up data. Internal validation was performed using bootstrapping. Results: Significant differences in baseline characteristics such as patient age, ethnicity, and disease severity existed between the treatment groups. Overall, 46 patients (2%) with complete data available had bowel dysfunction at baseline, including 11 (1%), 19 (4%), and 16 (3%) patients treated by RP, EBRT, and PI, respectively (p = 0.001). The overall rate of bowel dysfunction at 2 years in those patients with no bowel dysfunction at baseline was 2%, 10%, and 4% for patients treated by RP, EBRT, and PI, respectively (p < 0.001). In multivariable analysis, EBRT (p < 0.001), PI (p < 0.001), baseline bowel symptoms (p < 0.001), and institution (p = 0.04) were associated with bowel dysfunction. A nomogram based on the predictive parameters had a concordance index of 0.73 and predictions were well-calibrated with observed outcome. Conclusions: An externally validated nomogram that predicts 2-year incidence of bowel dysfunction after treatment for localized prostate cancer has been developed and may be useful for patient counseling regarding treatment options.