Capecitabine and oral cyclophosphamide: A novel oral treatment combination for advanced cancer

Background:  This dose escalation study assessed feasibility of a totally oral chemotherapy regimen using cyclophosphamide and capecitabine. The rationale for this combination was based on the observation that preclinical models of cyclophosphamide up‐regulated tumor thymidine phosphorylase and increased the activation of capecitabine. Methods:  Eligible patients with advanced cancer were treated with oral cyclophosphamide and capecitabine on a 28‐day cycle. If no dose limiting toxicities (DLT) were encountered during the first two treatment cycles, the next patient group was assigned to the next highest dose level until the maximum tolerable dose (MTD) was determined. Results:  Twenty‐seven patients entered treatment. The majority of non‐DLT were grades 1 and 2. DLT experienced in the first 8‐week observation period were grade 3 diarrhea (one patient, level III) and grade 3 emesis (two patients, level V). MTD was observed at level 5, 1331 mg/m 2 /day capecitabine days 1–28 with 125 mg/m 2 /day cyclophosphamide days 1–14 of the 28‐day cycle. The recommended phase II dose is therefore 1331 mg/m 2 /day capecitabine with 100 mg/m 2 /day cyclophosphamide. The best response evaluation showed four partial responses (breast, colon, ovary and pancreas). Conclusion:  Cyclophosphamide and capecitabine can be combined at their full oral single agent dose with promising tolerability and activity.