Erectile dysfunction is a common adverse effect of external beam radiation therapy for localized prostate cancer (PCa), likely as a result of damage to neural and vascular tissue. Magnetic resonance-guided online adaptive radiotherapy (MRgRT) enables high-resolution MR imaging and paves the way for neurovascular-sparing approaches, potentially lowering erectile dysfunction after radiotherapy for PCa. The aim of this study was to assess the planning feasibility of neurovascular-sparing MRgRT for localized PCa.
Twenty consecutive localized PCa patients, treated with standard 5×7.25 Gy MRgRT, were included. For these patients, neurovascular-sparing 5×7.25 Gy MRgRT plans were generated. Dose constraints for the neurovascular bundle (NVB), the internal pudendal artery (IPA), the corpus cavernosum (CC), and the penile bulb (PB) were established. Doses to regions of interest were compared between the neurovascular-sparing plans and the standard clinical pre-treatment plans.
Neurovascular-sparing constraints for the CC, and PB were met in all 20 patients. For the IPA, constraints were met in 19 (95%) patients bilaterally and 1 (5%) patient unilaterally. Constraints for the NVB were met in 8 (40%) patients bilaterally, in 8 (40%) patients unilaterally, and were not met in 4 (20%) patients. NVB constraints were not met when gross tumor volume (GTV) was located dorsolaterally in the prostate. Dose to the NVB, IPA, and CC was significantly lower in the neurovascular-sparing plans.
Neurovascular-sparing MRgRT for localized PCa is feasible in the planning setting. The extent of NVB sparing largely depends on the patient's GTV location in relation to the NVB.
Physics and imaging in radiation oncology. 2021 Sep 21*** epublish ***
Frederik R Teunissen, Ruud C Wortel, Jochem Hes, Thomas Willigenburg, Eline N de Groot-van Breugel, Johannes C J de Boer, Harm H E van Melick, Helena M Verkooijen, Jochem R N van der Voort van Zyp
Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands., Department of Urology, University Medical Center Utrecht, Utrecht, The Netherlands., Department of Urology, St. Antonius Hospital, Nieuwegein, Utrecht, The Netherlands., Imaging and Oncology Division, University Medical Center Utrecht, Utrecht, The Netherlands.