Stamp test delivers message on erectile dysfunction after high-dose intensity-modulated radiotherapy for prostate cancer

Objective: To evaluate erectile function after high-dose radiotherapy for prostate cancer using the International Index of Erectile Function, Expanded Prostate Cancer Index Composite, and stamp test. Methods: Men with favorable and intermediate-risk prostate cancer were assigned to receive prostate intensity-modulated radiotherapy (IMRT) versus an erectile tissue-sparing IMRT technique in a Phase III randomized, prospective study. The stamp test and International Index of Erectile Function and Expanded Prostate Cancer Index Composite questionnaires were completed at baseline and 6 months, 1 year, and 2 years after IMRT. The Sexual Health Inventory for Men scores were abstracted from the International Index of Erectile Function questionnaire. A partner questionnaire, designated IIEF-P, modeled after the International Index of Erectile Function questionnaire but from the perspective of the partner, was also collected. Results: The data from 94 men who were enrolled in the trial and who had completed <1 questionnaire or 1 stamp test were analyzed. The median age of the patient population was 62.5 years. The median radiation dose was 76 Gy (range 74-80). At 6 months and 1 year after high-dose IMRT, a positive stamp result correlated significantly with the median Expanded Prostate Cancer Index Composite sexual summary, sexual function, and bother subscale scores. Additionally, 6 months after IMRT, the stamp test correlated with the median International Index of Erectile Function, International Index of Erectile Function sexual function domain, and Sexual Health Inventory for Men scores. Robust concordance for the International Index of Erectile Function and Sexual Health Inventory for Men scores was appreciated between responding patient and partner pairs. Conclusion: Nocturnal tumescence, as indicated by a positive stamp test, correlated well with established quality of life questionnaires after IMRT. The stamp test should strongly be considered as an objective measure of erectile function in future studies of erectile dysfunction in patients with prostate cancer.