Dominant intraprostatic lesion boosting in sexual-sparing radiotherapy of prostate cancer: A planning feasibility study

Selena Ciabatti; Maria Ntreta; Milly Buwenge; Caterina Gaudiano; Elisa Sessagesimi; Fabrizio Romani; Anna L Angelini; Silvia Cammelli; Gabriella Macchia; Francesco Deodato; Alice Zamagni; Rita Golfieri; Alessio G Morganti; Savino Cilla

doi:10.1016/j.meddos.2019.01.008

Dominant intraprostatic lesion boosting in sexual-sparing radiotherapy of prostate cancer: A planning feasibility study

Med Dosim. 2019;44(4):356-364. doi: 10.1016/j.meddos.2019.01.008. Epub 2019 Apr 5.

Affiliations

¹ Radiation Oncology Unit, Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, S. Orsola-Malpighi Hospital, Bologna, Italy.
² Radiation Oncology Unit, Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, S. Orsola-Malpighi Hospital, Bologna, Italy. Electronic address: mbuwenge@gmail.com.
³ Radiology Unit, Department of Diagnostic Medicine and Prevention, S. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy.
⁴ Radiotherapy Unit, "Giovanni Paolo II" Foundation, Catholic University of Sacred Heart, Campobasso, Italy.
⁵ Medical Physics Unit, "Giovanni Paolo II" Foundation, Catholic University of Sacred Heart, Campobasso, Italy.

PMID: 30955990
DOI: 10.1016/j.meddos.2019.01.008

Abstract

Aim: Radical radiotherapy of prostate cancer requires a relatively high dose to achieve an optimal tumor control probability and a reduced dose to the critical structures related to the sexual function (S_OARs) in order to avoid erectile dysfunction. The aim of this study was to perform a planning feasibility analysis of a 3-level dose prescription with Simultaneous Integrated Boost (SIB) on the dominant intraprostatic lesion (DIL) and with S_OARs sparing.

Material and methods: Twelve patients with clinically localized intermediate risk prostate cancer were included. The prostate, seminal vescicles, and DIL Clinical Target Volumes were delineated on rigid fused MRI-CT simulation images using mp-MRI as a separate guide. A 5 mm margin was added to define the PTVs. Penile bulb (PB), corpora cavernosa (CC), internal pudendal arteries (IPAs) and neurovascular bundles were contoured as S_OARs. The following doses were prescribed in 25 fractions: 56.25 Gy to PTVsv, 67.50 Gy to PTVp, and 75 Gy to PTVdil. Standard plans (SD-VMAT) were created to fulfil targets coverage and Quantec constraints for conventional OARs (SD_OARs: rectum, bladder, and femoral heads). For each patient, a new "sexual-sparing" plan (SS-VMAT) was created adding new objectives for S_OARs with priority to minimize mean doses to IPAs, CC, and PB. Dose-volume histogram end points were compared between the 2 plans using Wilcoxon test.

Results: D_98% were >95% of prescribed doses for all targets and techniques. No significant differences were found in sparing SD_OARs for considered metrics. Regarding S_OARs, SS_VMAT plans provided a significant reduction of the dose. Mean dose reduction for IPAs, CC, PB, and neurovascular bundles was 32.4% (11.2 Gy, p = 0.002), 22.5% (4.1 Gy, p = 0.006), 10.0% (4.6 Gy, p = 0.010), and 2.6% (1.8 Gy, p = 0.020), respectively.

Conclusions: We showed that a significant dose sparing for S_OARs using VMAT-SIB strategy is feasible allowing "sexual-sparing" and highly conformal plans with dose escalation to the DIL.

Keywords: Boost; Dominant intraprostatic lesion; Prostate neoplasm; Radiotherapy; Sexual-sparing.

MeSH terms

Aged
Erectile Dysfunction / prevention & control*
Feasibility Studies
Humans
Magnetic Resonance Imaging
Male
Middle Aged
Organs at Risk / radiation effects*
Prostatic Neoplasms / diagnostic imaging
Prostatic Neoplasms / radiotherapy*
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted / methods*
Radiotherapy, Intensity-Modulated / methods*
Tomography, X-Ray Computed