OBJECTIVE: The aim of this study was to assess the toxicity of concomitant topotecan and radiation therapy in a Phase I study. Primary treatment for cervical carcinoma usually consists of surgery or radiation, with chemotherapy used in a neoadjuvant or concomitant fashion. There are in vitro data to suggest that topotecan is a radiosensitizing agent. METHODS: Six patients with cervical cancer were recruited to this study. All patients had completed whole pelvic radiation therapy and were scheduled for low-dose brachytherapy. The patients were administered topotecan IV during their low-dose brachytherapy. The initial dose of topotecan was 0.5 mg/m2/day for 5 days concomitant with low-dose brachytherapy for two brachytherapy applications. RESULTS: Three patients were accrued to the initial dose level. No major toxicity was noted at this dose level. Three patients were treated at the 1.0 mg/m2/day dose level; however, significant toxicity was noted at this level. (Two patients experienced grade 4 and one a grade 3 hematologic toxicity). CONCLUSION: Significant marrow toxicity was noted with concomitant topotecan and intracavitary radiation at 1.0 mg/m2/day. The maximum tolerated dose in this trial was 0.5 mg/m2/day for 5 days of topotecan concomitant with low-dose brachytherapy.