Simultaneous Integrated Boost–Intensity Modulated Radiation Therapy With Concomitant Capecitabine and Mitomycin C for Locally Advanced Anal Carcinoma: A Phase 1 Study

Abstract

Newer radiation techniques, and the application of continuous 5-FU exposure during radiation therapy using oral capecitabine may improve the treatment of anal cancer. This phase 1, dose-finding study assessed the feasibility and efficacy of simultaneous integrated boost-intensity modulated radiation therapy (SIB-IMRT) with concomitant capecitabine and mitomycin C in locally advanced anal cancer, including pharmacokinetic and pharmacogenetic analyses. Patients with locally advanced anal carcinoma were treated with SIB-IMRT in 33 daily fractions of 1.8 Gy to the primary tumor and macroscopically involved lymph nodes and 33 fractions of 1.5 Gy electively to the bilateral iliac and inguinal lymph node areas. Patients received a sequential radiation boost dose of 3 × 1.8 Gy on macroscopic residual tumor if this was still present in week 5 of treatment. Mitomycin C 10 mg/m(2) (maximum 15 mg) was administered intravenously on day 1, and capecitabine was given orally in a dose-escalated fashion (500-825 mg/m(2) b.i.d.) on irradiation days, until dose-limiting toxicity emerged in ≥2 of maximally 6 patients. An additional 8 patients were treated at the maximum tolerated dose (MTD). A total of 18 patients were included. The MTD of capecitabine was determined to be 825 mg/m(2) b.i.d. The predominant acute grade ≥3 toxicities included radiation dermatitis (50%), fatigue (22%), and pain (6%). Fifteen patients (83% [95%-CI: 66%-101%]) achieved a complete response, and 3 (17%) patients a partial response. With a median follow-up of 28 months, none of the complete responders, and 2 partial responders had relapsed. SIB-IMRT with concomitant single dose mitomycin C and capecitabine 825 mg/m(2) b.i.d. on irradiation days resulted in an acceptable safety profile, and proved to be a tolerable and effective treatment regimen for locally advanced anal cancer.