Long‐term outcomes of definitive radiation with volumetric modulated arc therapy and concurrent chemotherapy for squamous cell carcinoma of the anus in a regional Australian cancer centre

Introduction Concurrent chemoradiotherapy is the standard of care in the curative intent treatment of squamous cell carcinoma (SCC) of the anus. Volumetric arc therapy (VMAT) is a highly conformal radiation therapy technique that has been implemented to reduce toxicity for these patients. However, there are few reports evaluating the long‐term outcomes of VMAT. Thus, we evaluated the survival and toxicity outcomes of anal cancer patients treated in our regional cancer centre undergoing curative intent chemoradiotherapy using VMAT and following the Australian EviQ guidelines. Methods All consecutive patients treated with the VMAT technique for curative‐intent definitive chemoradiotherapy for anal SCC at our institution from 2013 until 2022 were retrospectively reviewed for survival and toxicity outcomes. Kaplan–Meier estimates of locoregional control, distant metastasis‐free survival, disease‐free survival, anal cancer‐specific survival and overall survival were obtained. Results In total, 44 patients were analysed. The median follow‐up was 48.9 months (Range 7.8–107). 97.7% of patients completed the prescribed radiation therapy and 88.6% chemotherapy. Five patients (11.4%) recurred. Four (9.1%) had isolated local failures, and one (2.3%) had an isolated distant failure. There were no regional nodal failures. The Kaplan–Meier estimates for locoregional control, distant metastasis‐free survival, disease‐free survival, anal cancer‐specific survival and overall survival were 90.3%, 97.7%, 88.1%, 97.1% and 87% at 3 years, and 90.3%, 97.7%, 88.1%, 93.0% and 72.3% at 5 years, respectively. Acute grade 3 genitourinary (GU), gastrointestinal (GI) and skin toxicities occurred in 2.2%, 6.8% and 13.6% of patients, respectively. There were no acute grade 4 toxicities. Late grade 2 GU and GI toxicities occurred in 6.8% and 11.3% of patients, respectively. There were no late grade 3 or 4 toxicities or treatment‐related deaths. The 5 ‐year colostomy‐free survival rate was 86.4%. Conclusion Outcomes for anal SCC after definitive chemoradiotherapy using VMAT in our regional cancer centre results in low rates of grade 3/4 toxicity, high rates of organ preservation and excellent survival outcomes.