Urethra-Sparing Prostate Cancer Stereotactic Body Radiation Therapy: Sexual Function and Radiation Dose to the Penile Bulb, the Crura, and the Internal Pudendal Arteries From a Randomized Phase 2 Trial
Vérane Achard, Thomas Zilli, Giorgio Lamanna, S. Jorcano, Samuel Bral, Carmen Rubio, Ângelo Oliveira, Marta Bottero, A. Bruynzeel, Roman İbrahimov, Heikki Minn, Zvi Symon, Guillaume Constantin, Raymond Miralbell
Abstract
PurposeErectile dysfunction (ED) is a common side effect after prostate cancer stereotactic body radiotherapy (SBRT). We aimed to assess the correlation between the dose to the penile bulb (PB), internal pudendal arteries (IPA), and crura with the development of ED after ultra-hypofractionation as part of a phase II clinical trial of urethra-sparing prostate SBRT.Material and methodsAmong the 170 patients with localized prostate cancer from 9 centers included in the trial, 90 men with CTCAE v4.03 grade 0-1 ED (ED-) at baseline treated with 36.25Gy in 5 fractions were selected for the present analysis. Doses delivered to the PB, crura, and IPA were analyzed and correlated with grade 2-3 ED (ED+) development. The impact on QoL assessed by the EORTC PR-25 questionnaire was reported.ResultsAfter a median follow-up of 6.5 years, 43% (n=39) of the patients developed ED+, while 57% (n=51) remained ED-. The dose delivered to the crura was significantly higher in ED+ patients than in ED- patients (7.7 Gy vs 3.6 Gy (p=0.014) for the Dmean and 18.5 Gy vs 7.2 Gy (p=0.015) for the D2%, respectively). No statistically significant difference between ED+ and ED- patients was observed for the dose delivered to the PB and the IPA. The median ED+ free-survival was worse in patients receiving a crura Dmean ≥ 4.7 Gy vs < 4.7 Gy (51.5% vs 71.7%, p=0.005), and a crura D2% >12 Gy vs ≤ 12 Gy (54.9% vs 68.9%, p =0.015). No ED+ free-survival differences were observed for doses delivered to PB and IPA. Decline in EORTC PR-25 sexual functioning was significantly more pronounced in patients with higher doses to the crura.ConclusionsBy keeping a Dmean and D2% to crura below 4.7 Gy and 12 Gy respectively, the risk to develop ED+ following prostate SBRT may be significantly reduced.