Preliminary results of combined therapy with topotecan and carboplatin in advanced non-small-cell lung cancer.

Topotecan is a topoisomerase I inhibitor and an analogue of camptothecin with demonstrated activity in small-cell lung cancer. However, less is known about the potential role of topotecan in advanced non-small-cell lung cancer (NSCLC). Platinum-based combination therapy is currently recommended in NSCLC patients presenting with good performance status. Because topotecan demonstrates a novel mechanism of action, its investigation in platinum combinations is warranted. In phase I/II trials of topotecan given as part of a cisplatin-based regimen, significant antitumor activity has been observed, providing the rationale for conducting further studies aimed at assessing survival benefit. However, this combination exhibits sequence dependence, with increasing hematologic toxicity observed when cisplatin is administered on day 1 of a 5-day topotecan course. Cisplatin has been associated with dose-limiting nonhematologic toxicities. Carboplatin exhibits a different toxicity profile compared with cisplatin, which makes it an attractive agent to study in combination. A hypothesis can be made that carboplatin in combination with newer agents such as topotecan might compare favorably with classic cisplatin-based regimens, particularly with respect to efficacy:toxicity ratio. Therefore, a phase II study was initiated to determine the efficacy, toxicity, and safety of carboplatin-topotecan combination in advanced NSCLC. Preliminary results reported here show that topotecan with carboplatin is generally well tolerated with manageable hematologic toxicity. Indirect comparison with cisplatin-topotecan combination suggests a lower incidence of dose-limiting nonhematologic toxicity. Whether or not the carboplatin-topotecan regimen is able to offer tumor response and survival benefit comparable to those observed with cisplatin-based combinations remains to be established.