Topoisomerase I inhibitors in the treatment of head and neck cancer.

Traditionally, the role of chemotherapy in the treatment of squamous carcinoma of the head and neck has been confined to patients with recurrent or metastatic disease who are deemed incurable with surgery or radiation therapy. Over the past decade, however, the role of chemotherapy has changed dramatically. The use of primary combined chemoradiation to preserve function or to enhance survival in patients with unresectable disease has become a standard approach. As the use of chemotherapy in squamous carcinoma of the head and neck has expanded, investigators have been interested in identifying new active agents. Topoisomerase I inhibitors, a new class of drugs, have been found to be active in a number of solid and hematologic malignancies. Three topoisomerase I inhibitors have been investigated in the treatment of metastatic or recurrent squamous carcinoma of the head and neck: 9-aminocamptothecin (9-AC), topotecan (Hycamtin), and irinotecan (CPT-11, Camptosar). Neither 9-AC nor topotecan has demonstrated clinically significant activity in the treatment of metastatic or recurrent squamous carcinoma of the head and neck. In contrast, irinotecan has demonstrated a modest overall response rate of 21.2% (95% confidence interval [CI] = 9%-38.9%), with a median survival of 214 days and a 1-year survival rate of 30.2%. The response and toxicity appear to be dose dependent. Further investigation of irinotecan in combination with other active agents and radiotherapy is warranted.