The role of VP-16 in the treatment of small-cell lung cancer: studies of the West of Scotland Lung Cancer Group.

Reviews of published studies indicate that the incorporation of VP-16 (Vepesid) into combination chemotherapy for small-cell lung cancer may improve overall response rates from 50% to between 65% and 80%. In addition, high-dose VP-16 may yield a higher response rate than that obtained with conventional doses. The West of Scotland Lung Cancer Group has therefore conducted studies to examine the effects of VP-16 both in a combination regimen as induction therapy and (together with high-dose cyclophosphamide) as late intensification therapy in high dose, aimed at preventing relapse in responding patients. Response to induction treatment improved with the addition of VP-16, compared to earlier studies carried out by the group, yielding an overall response rate of 80% for patients with limited disease and 62% for those with extensive disease. Although induction therapy comprised only three courses (lasting 9 weeks), the median response duration of 9.5 months for complete responders and the median survival of 14 months for complete responders (limited disease) were in keeping with those obtained using more prolonged induction therapy. The intensification therapy with high-dose cyclophosphamide and high-dose VP-16, however, yielded no improvement in overall survival in those responding patients who received it compared with those who did not. Radiotherapy following late-dose intensification prevented local tumor recurrence but appeared to have no effect on overall survival. Resistance to VP-16 and other drugs is a possible deterrent to successful therapy in small-cell lung cancer, and it is suggested that research focus on a possible role for calcium channel blockers in circumventing drug resistance.