Volumetric modulated arc therapy (VMAT) in the combined modality treatment of anal cancer patients.

Objective: To report clinical and dosimetric outcomes of a consecutive series of patients with anal cancer treated with volumetric-modulated arc therapy (VMAT) concomitant to chemotherapy (CT).

Methods: A cohort of 39 patients underwent VMAT employing a schedule consisting of 50.4 Gy/28 fractions to the gross tumour volume (GTV) and 42 Gy/28 fractions to the elective nodal volumes for patients with cT2N0 disease. Patients with cT3-T4/N0-N3 tumours were prescribed 54 Gy/30 fractions to the GTV and 50.4 Gy/30 fractions to the gross nodal volumes if sized ≤3 cm or 54 Gy/30 fractions if > 3 cm. Elective nodal regions were given 45 Gy/30 fractions. CT was administered concurrently following Nigro's regimen. The primary end point was acute toxicity. Secondary end points were colostomy-free survival (CFS), disease-free survival (DFS), cancer-specific survival (CSS) and overall survival (OS). Dosimetric data are also provided.

Results: Median follow-up was 21 months. Maximum acute toxicities were: dermatologic-G3: 18%; gastrointestinal-G3: 5%; genitourinary-G3: 2%; anaemia-G2: 7%; leukopenia-G3: 28%; G4: 8%; neutropenia-G3: 13%; G4: 18%; thrombocytopenia-G3: 11%; and G4: 2%. The actuarial 2-year CFS was 77.9% [95% confidence interval (CI): 54-90.4%]. Actuarial 2-year OS and CSS were 85.2% (95% CI: 60.1-95.1%), while DFS was 75.1% (95% CI: 52.4.7-88.1%).

Conclusion: Our clinical results support the use of VMAT as a safe and effective intensity-modulated radiotherapy (IMRT) option in the combined modality treatment of anal cancer, with consistent dosimetry, mild toxicity and promising sphincter preservation and survival rates.

Advances In Knowledge: IMRT is a standard of care for patients with anal cancer, and VMAT is a robust technical solution in this setting.