Suramin in patients with metastatic colorectal cancer pretreated with fluoropyrimidine-based chemotherapy. A phase II study.

BACKGROUND

The results of conventional chemotherapy in metastatic colorectal cancer are discouraging, making it a logical target for new treatment approaches a necessary consideration. Suramin is a polysulfonated naphthylurea that binds to several cellular growth factors and has in vitro activity against human colorectal cancer cells. Therefore, this Phase II study of patients with metastatic colorectal cancer was conducted to evaluate its clinical activity.

METHODS

Suramin was administered as a 6-day continuous infusion every week for 8 consecutive weeks by using a computer-assisted dosing of Bayesan pharmacokinetics to maintain suramin plasma concentrations of 200-250 micrograms/ml. Twenty patients with metastatic colorectal cancer who were not responsive or in progression within 6 months after completing fluoropyrimidine-based chemotherapy entered the study.

RESULTS

Toxicities included mostly Grade 1 and 2 fatigue, nausea and vomiting, peripheral neurotoxicity, creatinine elevation, and proteinuria. No objective responses were observed, but three of three patients who received 5-fluorouracil plus folinic acid after suramin achieved a partial response.

CONCLUSIONS

These results indicate that suramin is inactive in patients with metastatic colorectal cancer pretreated with fluoropyrimidines. Pretreatment with suramin may have changed the biology of the tumor, sensitizing it to fluoropyrimidines. Studies to investigate this possibility are in progress.