A systematic review on the role of interventional radiotherapy for treatment of anal squamous cell cancer: multimodal and multidisciplinary therapeutic approach

Background: Aim was to compare the efficacy of interventional radiotherapy (IRT) boost vs. external beam radiotherapy (EBRT) boost after chemoradiation (CCRT) in patients with anal cancer (AC). Methods: The P.I.C.O. framework was: in patients with AC [P], is IRT boost [I] superior to EBRT boost [C] in terms of local control (LC), cancer specific survival (CSS), overall survival (OS), distant meta-static free Survival (DMFS), colostomy free survival (CFS) and toxicity [O]? Results: 651 patients were analyzed. The median 5-year locoregional control rates was 87.8% in the IRT boost group versus 72.8% in the EBRT boost group. The 5-year cancer-specific survival rate was 91% in the IRT boost group versus 78% in the EBRT boost group. 5-years overall survival was 74.6% in IRT boost versus 67.7% in the EBRT boost. 5-years disease metastasis-free survival rate was 92.9% in IRT boost group vs. 85.6% for the EBRT boost group. Cancer-free survival rate was 76.8% in the IRT group vs. 63.1% in the EBRT boost group. Acute toxicity above grade 2 was less common in the IRT boost group while chronic toxicity was similar between both groups. Conclusion: IRT boost after CCRT could lead to better outcomes than EBRT boost in treating AC.