High-tailored Anal Canal Radiotherapy (HIT-ART): Outcomes of a 10-Year Single Center Clinical Experience.

Abstract

The current standard for anal cancer treatment is essentially a 'one size fits all' approach where the dose of radiotherapy is similar whether the tumor is very small or very large. Trials are ongoing to evaluate dose de-escalation or escalation in localized disease depending on tumor size. The aim of the study was to assess results of a personalized approach involving dose stratification by stage and boost dose adjusted according to tumor early response. We retrospectively reviewed squamous cell anal cancer (SCAC) patients treated between 2011 and 2021 by long-course intensity-modulated radiotherapy (IMRT) and concomitant chemotherapy (CT); a sequential boost could be administered by IMRT or interventional radiotherapy (IRT) to obtain a total equivalent dose in 2 Gy (EQD2) of 54-60 Gy. We analyzed 110 patients (61% T3-4 stage, 71% node-positive). A total of 68.2% of patients received a sequential boost, mainly by IRT; median total EQD2 to primary site was 59.3 Gy. Acute ≥G3 toxicity rate was 36.4%. Median follow-up (FUP) was 35.4 months. A total of 83% of patients achieved clinical complete response (cCR); locoregional recurrence (LRR) occurred in 20.9% and distant metastases in 6.4% of cases. A total of 12.7% patients underwent salvage surgery. A total of 25.5% of patients reported ≥G2 and 4.5% ≥G3 late toxicity. The estimated 3-year overall survival, disease-free survival and colostomy-free survival were 92%, 72% and 84% respectively; 3-year-LRR was 22%. Nodal stage was associated with poorer cCR probability and higher LRR (p<0.05). Our results on a large cohort of patients with locally advanced SCAC and long FUP time confirmed the efficacy of IMRT; high local control and manageable toxicity also suggest IRT as a promising method in treatment personalization.