Doxorubicin in combination with verapamil in advanced colorectal cancer. A phase II trial

The possibility that verapamil might increase the sensibility of colorectal carcinomas to doxorubicin was studied in 24 patients without previous cytotoxic chemotherapy. The treatment started with oral verapamil, which was escalated up to the individual maximum tolerable dose (defined by prolongation of P-Q in ECG, fall in blood pressure, or dizziness). The median maximum tolerable dose was 600 mg (range 320-1,440 mg). During continued verapamil administration the patients then got weekly infusions of doxorubicin, 25 mg/m2. The median number of doxorubicin courses was 8 (range 2-22). Among 21 patients evaluable for response and toxicity two partial remissions occurred but no complete remission. The study did not indicate enhanced cardiac, hematological or non-hematological toxicity from the combined treatment.