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

Background/aim: 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.

Patients And Methods: 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.

Results: 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).

Conclusion: 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.