Clinical outcomes with dose-escalated adaptive radiotherapy for urinary bladder cancer: A prospective study
Menée sur 44 patientes atteintes d'un cancer de la vessie de stade localisé (durée médiane de suivi : 30 mois), cette étude évalue, dans le cadre d'un traitement trimodal épargnant la vessie, la faisabilité et la toxicité d'une radiothérapie adaptative avec escalade de dose et guidage par l'imagerie
Purpose : To assess feasibility, clinical outcomes and toxicity in patients with bladder cancer treated with adaptive, image guided radiotherapy (IGRT) for bladder preservation as a part of trimodality treatment. The role of dose escalation was also studied. Methods and materials : Forty four patients with localized bladder cancer were enrolled in a prospective study. They underwent maximal safe resection of bladder tumor and concurrent platinum based chemotherapy. Patients with large tumors were offered induction chemotherapy. Radiotherapy planning was done using either 3 (n=34) or 6 (n=10) concentrically grown Planning Target Volumes (PTV). Patients received 64Gy in 32 fractions to the whole bladder and 55Gy to the pelvic nodes, and if appropriate, a simultaneous integrated boost to the tumor bed to 68Gy (EQD210=68.7Gy). Daily megavoltage(MV) imaging helped to choose the most appropriate PTV encompassing bladder for the particular day (plan of the day). Results : Most patients (88%) had T2 disease. Sixteen (36%) patients received neoadjuvant chemotherapy. Majority of the patients (73%) received prophylactic nodal irradiation while 55% patients received escalated dose to the tumor bed. With a median follow up of 30 months, the 3 year locoregional control (LRC), disease free survival and overall survival (OAS) were 78%, 66%, and 67% respectively. The bladder preservation rate was 83%. LRC (87% vs 68%, p= 0.748) and OAS (74% vs 60%, p=0.36) were better in patients receiving dose escalation. Acute and late RTOG Grade III genitourinary toxicity was seen in 5 (11%) and 2 (4%) patients respectively. There was no acute or late RTOG grade III or higher gastrointestinal toxicity. Conclusion : Adaptive IGRT using plan of the day approach for bladder preservation is clinically feasible with good oncological outcomes and low rates of acute and late toxicities. Dose escalation is safe and possibly improves outcomes in bladder preservation.