Baseline status and dose to the penile bulb predict impotence 1 year after radiotherapy for prostate cancer.

AIM - To assess the predictors of the onset of impotence 1 year after radiotherapy for prostate cancer.

PATIENT AND METHODS - In a multi-centric prospective study, the International Index of Erectile Function (IIEF) questionnaire-based potency of 91 hormone-naïve and potent patients (IIEF1-5 > 11 before radiotherapy) was assessed.

At the time of this analysis, information on potency 1 year after treatment was available for 62 of 91 patients (42 treated with hypofractionation: 2.35-2.65 Gy/fr, 70-74.2 Gy; 20 with conventional fractionation: 74-78 Gy). Prospectively collected individual information and Dmax/Dmean to the penile bulb were available; the corresponding 2 Gy-equivalent values (EQD2_max/EQD2_mean) were also considered. Predictors of 1‑year impotency were assessed through uni- and multi-variable backward logistic regression: The best cut-off values discriminating between potent and impotent patients were assessed by ROC analyses. The discriminative power of the models and goodness-of-fit were measured by AUC analysis and the Hosmer-Lemeshow (H&L) test.

RESULTS - At 1‑year follow-up, 26 of 62 patients (42 %) became impotent. The only predictive variables were baseline IIEF1-5 values (best cut-off baseline IIEF1-5 ≥ 19), Dmax ≥ 68.5 Gy and EQD2_max ≥ 74.2 Gy. The risk of 1‑year impotence may be predicted by a two-variable model including baseline IIEF1-5 (OR: 0.80, p = 0.003) and EQD2_max ≥ 74.2 Gy (OR: 4.1, p = 0.022). The AUC of the model was 0.77 (95% CI: 0.64-0.87, p = 0.0007, H&L: p = 0.62). The 1‑year risk of impotency after high-dose radiotherapy in potent men depends on the EQD2_max to the penile bulb and on baseline IIEF1-5 values.

CONCLUSIONS - A significant reduction in the risk may be expected mainly when sparing the bulb in patients with no/mild baseline impotency (IIEF1-5 > 17).

Strahlentherapie und Onkologie : Organ der Deutschen Rontgengesellschaft ... [et al]. 2016 Apr 14 [Epub ahead of print]

Cesare Cozzarini, Tiziana Rancati, Fabio Badenchini, Federica Palorini, Barbara Avuzzi, Claudio Degli Esposti, Giuseppe Girelli, Ilaria Improta, Vittorio Vavassori, Riccardo Valdagni, Claudio Fiorino

Radiotherapy, San Raffaele Scientific Institute, Milano, Italy., Prostate Cancer Program, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy., Radiotherapy, San Raffaele Scientific Institute, Milano, Italy., Medical Physics, San Raffaele Scientific Institute, Milan, Italy., Radiation Oncology 1, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy., Radiotherapy, Ospedale Bellaria, Bologna, Italy., Radiotherapy, Ospedale ASL9, Ivrea, Italy., Medical Physics, San Raffaele Scientific Institute, Milan, Italy., Radiotherapy, Cliniche Gavazzeni-Humanitas, Bergamo, Italy., Prostate Cancer Program, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy., Medical Physics, San Raffaele Scientific Institute, Milan, Italy. .

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