Image-guided IMRT with simultaneous integrated boost as per RTOG 0529 for the treatment of anal cancer

Aim To report on clinical outcomes of simultaneous integrated boost intensity-modulated radiation therapy (IMRT) and concurrent chemotherapy as per Radiation Therapy Oncology Group (RTOG) 0529 protocol in anal cancer patients. Methods Clinical stage T1–T4 N0–N3 anal cancer patients were submitted to concomitant chemoradiation. Patients with cT2N0 disease were prescribed 50.4 Gy/28 fractions to the gross tumor planning target volume (PTV) and 42 Gy/28 fractions to the elective nodal PTV. Patients staged as cT3–T4/N0–N3 were given 54 Gy/30 fractions to the macroscopic anal PTV, while clinical nodes were prescribed 50.4 Gy/30 fractions if <3 cm or 54 Gy/30 fractions if ≥3 cm; elective nodal PTV was prescribed 45 Gy/30 fractions. Two cycles of concomitant 5-fluorouracil and mitomycin C were planned for all patients. Oncological outcomes, acute and late toxicity profiles and pattern of failure were reported. Results The 3-year colostomy-free survival rate was 64% (95% CI 0.52–0.75). The 3-year local control, disease-free and overall survival rates were 69% (95% CI 0.57–0.79), 71% (95% CI 0.59–0.80) and 79% (95% CI 0.66–0.87), respectively. The cumulative incidence of colostomies was 15.1% (95% CI 8.15–23.88) at 24 months. The cumulative incidence of cancer-specific deaths was 16.4% (95% CI 8.60–26.47) at 36 months. Major acute toxicity consisted of hematological (G3–G4: 26%) and cutaneous (G3–G4: 16%) events. Only one case of ≥G3 late toxicity was documented. Conclusions Simultaneous integrated boost IMRT and concurrent chemotherapy as per RTOG 0529 protocol seems to be safe and feasible with consistent oncological outcomes and a mild acute and late toxicity profile in anal cancer patients.