Initial report of pencil beam scanning proton therapy for posthysterectomy patients with gynecologic cancer
Menée sur 11 patientes atteintes d'un cancer gynécologique (vagin, col de l'utérus ou endomètre) traité par radiothérapie en combinaison ou non avec une chimiothérapie et ayant subi une hystérectomie pour des lésions cancéreuses ou non (âge médian : 55 ans), cette étude évalue la toxicité aiguë d'une radiothérapie par faisceaux de protons de l'ensemble de la région pelvienne, puis compare les avantages dosimétriques de ce traitement par rapport à une radiothérapie avec modulation d'intensité
Purpose : To report the acute toxicities associated with pencil beam scanning proton beam radiotherapy (PBS) for whole pelvis radiotherapy in women with gynecologic cancers and a dosimetric comparison of PBS vs intensity modulated radiation therapy (IMRT) plans. Methods and Materials : Eleven patients with gynecologic cancer who were posthysterectomy received PBS to the whole pelvis. Patients received a dose of 45-50.4 Gy relative biological effectiveness (RBE) in 1.8 Gy(RBE) daily fractions. Acute toxicity was scored according to the CTCAEv4.0. A dosimetric comparison between two posterior oblique beam PBS and IMRT plans was conducted. The Wilcoxon signed rank test was used to assess the potential dosimetric differences between the two plans and PBS target coverage robustness relative to setup uncertainties. Results : Median age of patients was 55 years (23-76). Primary site was cervical (7), vaginal (1), or endometrial cancer (3). Patients received concurrent cisplatin (7), sandwich carboplatin/paclitaxel chemotherapy (1), both sandwich and concurrent (1), concurrent and adjuvant chemotherapy (1), or no chemotherapy (1). All patients completed treatment. Amongst the nine patients that received concurrent chemotherapy, the rate of grade 2 and 3 hematologic toxicities was 33% and 11%, respectively. There was 1 (9%) grade 3 acute gastrointestinal toxicity and no grade ≥3 genitourinary toxicity. The V10 –V30 of pelvic bone marrow, bladder, and small bowel were significantly lower with PBS vs IMRT, p<0.001. The target coverage for all PBS plans was robust relative to setup uncertainties (p>0.05) with CTV D95 and CTV D98 coverage changes within 2% for individual plans. Conclusions : Our results demonstrate the clinical feasibility of PBS and the dosimetric advantages particularly in the low dose sparing of normal tissues in the pelvis while target robustness is maintained relative to setup uncertainties. Future studies with larger patient numbers are planned to further validate our preliminary findings.