High-Dose Split-Course Radiation Therapy for Anal Cancer: Outcome Analysis Regarding the Boost Strategy (CORS-03 Study)

Purpose To retrospectively assess the clinical outcome in anal cancer patients treated with split-course radiation therapy and boosted through external-beam radiation therapy (EBRT) or brachytherapy (BCT). Methods and Materials From January 2000 to December 2004, a selected group (162 patients) with invasive nonmetastatic anal squamous cell carcinoma was studied. Tumor staging reported was T1 = 31 patients (19%), T2 = 77 patients (48%), T3 = 42 patients (26%), and T4= 12 patients (7%). Lymph node status was N0–1 (86%) and N2–3 (14%). Patients underwent a first course of EBRT: mean dose 45.1 Gy (range, 39.5–50) followed by a boost: mean dose 17.9 Gy (range, 8–25) using EBRT (76 patients, 47%) or BCT (86 patients, 53%). All characteristics of patients and tumors were well balanced between the BCT and EBRT groups. Results The mean overall treatment time (OTT) was 82 days (range, 45–143) and 67 days (range, 37–128) for the EBRT and BCT groups, respectively ( p p = 0.03), boost technique (BCT = 12% vs. EBRT = 33%, p = 0.002) and OTT (OTT p = 0.005). In the multivariate analysis, BCT boost was the unique prognostic factor (hazard ratio = 0.62 (0.41–0.92). In the subgroup of patients with OTT p = 0.03). In the case of OTT ≥80 days, the 5-year CRLR was not affected by the boost technique (BCT = 29% vs. EBRT = 38%, p = 0.21). Conclusion In anal cancer, when OTT is