Single-agent DTIC versus combination chemotherapy with or without immunotherapy in metastatic melanoma: a meta-analysis of 3273 patients from 20 randomized trials

It is currently unclear whether any combination therapy for the treatment of metastatic melanoma is superior to standard single-agent dacarbazine (DTIC) in terms of tumour response and overall survival. The available randomized clinical trial data were combined in a meta-analysis to address this question. Initially a thorough MEDLARS search was conducted covering the time period from January 1970 to January 1999. This literature search was supplemented by manual searches of study bibliographies (including review articles) and review of relevant textbooks. The meta-analysis was performed according to a prospective protocol using strict study eligibility criteria. Data derived from randomized controlled trials comparing single-agent DTIC with combination chemo/immunotherapy were combined using a fixed effects model. Data were stratified into three combination therapy groups: DTIC-containing regimens, non-DTIC-containing therapy, and chemotherapy plus immunotherapy. The primary outcome of interest was the proportion of patients demonstrating a complete or partial response to treatment. A total of 20 randomized trials comprising 3273 patients were initially combined in a meta-analysis. This yielded an odds ratio (OR) of 1.23 (95% confidence interval [CI] 1.02-1.48), demonstrating that combination drug therapies are associated with a 23% increase in response rate compared with single-agent DTIC. The combination of DTIC plus interferon-alpha produced a tumour response rate 53% greater (95% CI 1.10-2.13) than that seen with DTIC alone. This increase was greater than that seen with DTIC-containing multi-drug regimens, which had an OR of 1.33 (95% CI 0.99-1.78). No difference in overall survival was demonstrated. Non-DTIC-containing treatment programmes showed no advantage over DTIC in terms of tumour response rate (OR = 0.77, 95% CI 0.45-1.32). The combination of DTIC and interferon-alpha appears more active than standard single-agent DTIC in metastatic melanoma. Further randomized clinical trials employing a DTIC plus interferon arm are necessary to confirm these results.