Moderate Hypofractionated Postprostatectomy Volumetric Modulated Arc Therapy With Daily Image Guidance (VMAT-IGRT): A Mono-institutional Report on Feasibility and Acute Toxicity

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IntroductionThe aim of this study was to evaluate the acute toxicity profiles of a moderate hypofractionated regimen with volumetric modulated arc therapy (VMAT) in patients with prostate cancer (PC) who underwent radical prostatectomy.Material and MethodsFrom December 2012 to February 2016, 125 patients, previously having undergone radical prostatectomy, received adjuvant (64 patients) or salvage (61 patients) radiotherapy (RT) inside an institutional protocol of moderate hypofractionation schedule using the VMAT technique (Varian RapidArc, Palo Alto, CA). Eligible patients were < 85 years old, with an Eastern Cooperative Oncology Group performance status of 0 to 2, histologically proven adenocarcinoma of the prostate without distant metastases, and pathologic stage pT2-4 N0-1, with at least 1 of the following risk factors: capsular perforation, positive surgical margins, seminal vesicle invasion, and/or postoperative prostate-specific antigen > 0.2 ng/mL. Patients were stratified into low (1%), intermediate (9%), and high-risk (90%) groups. The median age was 68 years. The median doses were 66 Gy (range, 65.5-71.4 Gy) to the prostatic bed and 52.5 Gy (range, 50.4-54 Gy) to the pelvic lymph nodes, in 28 or 30 fractions. The acute genitourinary (GU) and gastrointestinal (GI) toxicities were scored according to the Common Terminology Criteria for Adverse Events, v4.ResultsAll 125 patients completed the planned treatment, with good tolerance. After RT, the median follow-up was 18 months. Acute toxicities were recorded for the GU (G0, 45/125 [36%]; G1, 63/125 [50.4%]; G2, 16/125 [12.8%]; G3, 1/125 [0.8%]) and the GI (G0, 42/125 [33.6%]; G1, 72/125 [57.6%]; G2, 11/125 [8.8%]; no G3). Analyzing data according to RT intent, a higher rate of GU toxicity ≥ 2 was found in the adjuvant setting (17.1%) with respect to the salvage group (9.8%); P = .01 with the Fisher exact text. Furthermore, at statistical analysis, no difference was found between the type of surgery (robotic, laparoscopic, or open) and incidence of urinary incontinence (P = .8). The actuarial Kaplan-Meier rates for biochemical disease-free survival were 94% and 77% for adjuvant and salvage RT, at 36 months.ConclusionsModerate hypofractionated postoperative RT with VMAT was feasible and safe with acceptable acute GU and GI toxicities. Longer follow-up is needed to assess late toxicity and clinical outcomes.Micro-AbstractIn prostate cancer, moderate hypofractionated postoperative radiotherapy with the volumetric modulated arc therapy technique is a promising option. Our series seems to confirm the feasibility and the good acute genitourinary and gastrointestinal toxicity profile comparable with conventional fractionation schedules. Longer follow-up is needed to evaluate late toxicity and clinical outcomes.

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