Late toxicity of moderately hypofractionated intensity-modulated proton therapy treating the prostate and pelvic lymph nodes for high-risk prostate cancer
Menée entre 2016 et 2018 auprès de 56 patients atteints d'un cancer de la prostate à haut risque de récidive (âge médian : 75,5 ans ; durée médiane de suivi : 43,9 mois), cette étude analyse la toxicité gastro-intestinale et génito-urinaire tardive associée à une protonthérapie à modulation d'intensité modérément hypofractionnée ciblant la prostate et les ganglions lymphatiques pelviens
Purpose: To evaluate late gastrointestinal (GI) and genitourinary (GU) toxicity of moderately hypofractionated intensity-modulated proton therapy (IMPT) targeting the prostate and pelvic lymph nodes. Methods and Materials: A target accrual of 56 patients with high-risk or unfavorable intermediate risk prostate cancer were enrolled into a prospective study of moderately hypofractionated IMPT. IMPT with pencil beam scanning was utilized to deliver 6750 and 4500 cGy RBE in 25 daily fractions simultaneously to the prostate and pelvic lymph nodes, respectively. All received androgen deprivation therapy. Late GI and GU toxicity was prospectively assessed using CTCAE v4.0, at baseline, weekly during radiotherapy, 3-month post-radiotherapy, and then every six months. Actuarial rates of late GI and GU toxicity were estimated using Kaplan-Meier method. Results: Median age was 75.5 years. Fifty-four patients were available for late toxicity evaluation. Median follow-up was 43.9 months (range: 16-66). The actuarial rate of late grade ≥ 2 GI toxicity at both 2 and 3 years was 7.4% (95% CI: 0.2-14.2%). The actuarial rate of late grade 3 GI toxicity at both 2 and 3 years was 1.9% (95% CI: 0-5.4%). One patient experienced grade 3 GI toxicity with proctitis. The actuarial rate of late grade ≥ 2 GU toxicity was 20.5% (95% CI: 8.9-30.6%) at 2 years, and 29.2 % (95% CI: 15.5-40.7%) at 3 years. None had grade 3 GU toxicity. The presence of baseline GU symptoms was associated with a higher likelihood of experiencing late grade 2 GU toxicity. Conclusions: A moderately hypofractionated IMPT targeting the prostate and regional pelvic lymph nodes was generally well tolerated. Patients with pre-existing GU symptoms had a higher rate of late grade 2 GU toxicity. A phase III study is needed to assess any therapeutic gain of IMPT, in comparison with photon-based radiotherapy.
International Journal of Radiation Oncology, Biology, Physics 2022