PET-CT guided SIB-IMRT combined with concurrent 5-FU/MMC for the treatment of anal cancer

Background: To evaluate local control (LC), survival and toxicity in anal cancer patients treated with intensity-modulated radiation therapy (IMRT) and concurrent chemotherapy at a single institution.Material and methods: From August 2010 to May 2015, 26 patients were treated at our institution with IMRT and concurrent 5-fluorouracil/mitomycin-C (5-FU/MMC) for localized squamous cell carcinoma of the anal canal (SCCAC). Radiotherapy (RT) with 50.4-60Gy was delivered with a sequential boost in 31%, and a simultaneous-integrated boost (SIB-IMRT) in 69% of cases. Initial staging was based on PET-CT and MRI. Clinical measures of interest were the influence of PET-CT on staging and treatment planning, LC, disease free survival (DFS), overall survival (OS), colostomy free survival (CFS) and toxicities.Results: Median age was 61 years, 22 patients (85%) were female, and no patient was HIV-positive. The proportion of patients with stage I, II, IIIA and IIIB disease was 15%, 35%, 23% and 27%, respectively. PET-CT modified the extent of nodal disease in 9/23 cases (39%) and lead to major changes in treatment planning in 4/23 patients (17%). MRI was more accurate at identifying T4 disease. RT was delivered at full dose in 26 patients (100%) and chemotherapy in 22/26 patients (85%). Two patients (7.7%) required RT breaks. Median follow-up was 35 months [IQR: 19-52]. The 2-year LC, DFS, OS and CFS were 100%, 100%, 100% and 92%. Acute grade 3 dermatitis and diarrhea occurred in 73% and 8% of cases, respectively. Grade 3-4 neutropenia was seen in 10/23 patients (43%). Four patients (15%) developed chronic grade 2 GI toxicity.Conclusions: PET-CT provided additional information leading to major changes in treatment planning for 17% of patients. Considering our excellent outcomes, routine use of PET-CT as standard staging modality and IMRT planning procedure appears justified for patients with SCCAC.