180 Low-dose metronomic cyclophosphamide induced sustained hypoxia in human tumor xenografts, which can be exploited therapeutically by the combination with the hypoxic cell cytotoxin tirapazamine

Abstract

Purpose: Reirradiation (re-RT) with concurrent chemotherapy offers a therapeutic option in patients who have locoregional recurrence of head and neck cancer (HNC). The hypoxic cell sensitizer, tirapazamine (TPZ), has demonstrated promising results in first-line therapy for HNC. This phase I trial was designed to test the feasibility of giving TPZ in the re-RT setting.Methods and Materials: Patients with recurrent HNC who received prior radiotherapy (RT) were enrolled and received TPZ (260 mg/m2) and cisplatin (50 mg/m2) Weeks 1, 3, and 5 concurrently with RT (72 Gy, 42 fractions over 6 weeks). TPZ (160 mg/m2) alone was added on Days 1, 3, and 5 of Week 2 (cohort 1) or Weeks 2 and 4 (cohort 2).Results: Twenty-five subjects were enrolled, 7 and 18 on cohorts 1 and 2, respectively. Significant toxicities included Grade 3 dermatitis (20%) and Grade 3 mucositis (40%). Dose-limiting toxicity was observed on cohort 2 (1 patient with aspiration pneumonia). Four deaths occurred during treatment. Two fatalities occurred after completing therapy as a result of carotid artery rupture. With a minimum and median follow-up of 14 and 24 months, respectively, median overall survival was 14 months with actuarial 1-year and 2-year survival of 56% and 27%, respectively.Conclusion: Reirradiation with concomitant chemotherapy including TPZ in patients with unresectable recurrent HNC is feasible and results in long-term survival in a significant proportion of patients.