Defining the potential for sexual structures-sparing for prostate cancer external beam radiotherapy: A dosimetric study

Jennifer Le Guevelou; Ayad Houssayni; Stéphane Key; Axel Largent; Caroline Lafond; Oscar Acosta; Antoine Simon; Renaud de Crevoisier; Anaïs Barateau

doi:10.1016/j.canrad.2024.05.008

Defining the potential for sexual structures-sparing for prostate cancer external beam radiotherapy: A dosimetric study

Cancer Radiother. 2024 Nov 7:S1278-3218(24)00199-9. doi: 10.1016/j.canrad.2024.05.008. Online ahead of print.

Authors

Jennifer Le Guevelou¹, Ayad Houssayni², Stéphane Key³, Axel Largent², Caroline Lafond⁴, Oscar Acosta², Antoine Simon², Renaud de Crevoisier³, Anaïs Barateau⁴

Affiliations

¹ Department of Radiotherapy, centre Eugène-Marquis, 35000 Rennes, France. Electronic address: jennifer.leguevelou@gmail.com.
² Université de Rennes, Inserm, LTSI, UMR 1099, 35000 Rennes, France.
³ Department of Radiotherapy, centre Eugène-Marquis, 35000 Rennes, France.
⁴ Department of Physics, centre Eugène-Marquis, 35000 Rennes, France.

PMID: 39516122
DOI: 10.1016/j.canrad.2024.05.008

Abstract

Purpose: The purpose of the study was to evaluate the dosimetric impact of sexual-sparing radiotherapy for prostate cancer, with magnetic resonance-only treatment planning.

Material and methods: Fifteen consecutive patients receiving prostate cancer radiotherapy were selected. A synthetic CT was generated with a deep learning method from each T2-weighted MRI performed at the time of treatment planning. For each patient, two plans were performed: standard treatment planning and sexual-structures sparing treatment planning. The treatment plan was designed to deliver a dose of 78Gy to the prostate and 50Gy to the seminal vesicles in 2Gy daily fractions, using volumetric arc therapy. Dose-volume histograms were computed to compare treatment plans.

Results: All plans fulfilled dosimetric objectives and were equivalent regarding planning target volume coverage. The doses delivered to both rectum, bladder, and femoral heads were similar between plans (P=0.20). Sexual-sparing plans enabled to decrease all dosimetric parameters on sexual organs-at-risk. The mean penile bulb dose in sexual-sparing plans was significantly reduced (21.1Gy±20.7 versus 13.4Gy±14.0, P<0.01), however with large variability observed between individuals. The mean dose delivered to the corpora cavernosa was also significantly reduced within sexual-sparing plans (13.1Gy±16.7 versus 8.6Gy±10.4, P<0.01). A significant reduction was also observed in the highest doses delivered to internal pudendal arteries (D10%: 48.4Gy±8.3 versus 33.1Gy±4.6, P<0.05; D5%: 52.0Gy±8.7 versus 36.8Gy±5.5, P<0.05).

Conclusion: Sparing of sexual structures appears feasible, without compromising neither planning target volume coverage nor doses delivered to non-sexual organs at risk. The clinical significance of this dose-reduction requires prospective evaluation.

Keywords: Cancer de prostate; IRM; MRI; Prostate cancer; Radiotherapy; Radiothérapie; Scanographie synthétique; Sexual structures; Sparing; Structures sexuelles; Synthetic CT; Épargne.