Dose-painted intensity-modulated radiation therapy for anal cancer: a multi-institutional report of acute toxicity and response to therapy.

PURPOSE: Chemoradiation for anal cancer yields effective tumor control, but is associated with significant acute toxicity. We report our multi-institutional experience using dose-painted IMRT (DP-IMRT). PATIENTS AND METHODS: Between August 2005 and May 2009, 43 patients were treated with DP-IMRT and concurrent chemotherapy for biopsy-proven, squamous cell carcinoma of the anal canal at two academic medical centers. DP-IMRT was prescribed as follows: T2N0: 42 Gy, 1.5 Gy/fraction (fx) to elective nodal planning target volume (PTV) and 50.4 Gy, 1.8 Gy/fx to anal tumor PTV; T3-4N0-3: 45 Gy, 1.5 Gy/fx to elective nodal PTV, and 54 Gy, 1.8 Gy/fx to the anal tumor and metastatic nodal PTV >3 cm with 50.4 Gy, 1.68 Gy/fx to nodal PTVs ≤ 3 cm in size. Acute and late toxicity was reported by the treating physician. Actuarial analysis was performed using the Kaplan-Meier method. RESULTS: Median age was 58 years; 67% female; 16% Stage I, 37% II; 42% III; 5% IV. Fourteen patients were immunocompromised: 21% HIV-positive and 12% on chronic immunosuppression. Median follow-up was 24 months (range, 0.6-43.5 months). Sixty percent completed chemoradiation without treatment interruption; median duration of treatment interruption was 2 days (range, 2-24 days). Acute Grade 3+ toxicity included: hematologic 51%, dermatologic 10%, gastrointestinal 7%, and genitourinary 7%. Two-year local control, overall survival, colostomy-free survival, and metastasis-free survival were 95%, 94%, 90%, and 92%, respectively. CONCLUSIONS: Dose-painted IMRT appears effective and well-tolerated as part of a chemoradiation therapy regimen for the treatment of anal canal cancer.