Tamoxifen in the treatment of metastatic malignant melanoma: still a controversy? (Review).

Abstract

This review attempts to summarize the available preclinical and clinical evidence supporting the inclusion of tamoxifen (TAM) in the treatment of malignant melanoma, in the attempt to identify what role, if any, the antiestrogen could have in the present and future therapeutic approach to this disease. Emphasis has been given to the biological basis of the potential TAM mechanisms of action, as well as to the rational basis underlying the study design of the reported clinical experiences. Results to date show that TAM has no useful activity as a single agent in melanoma patients, most published response rates reaching less than 10%. A still controversial question is the inclusion of the antiestrogen in different active chemotherapy regimens, since clinical investigations on the role of TAM in combination therapy of advanced melanoma have produced inconclusive results. While several early trials suggested that TAM may improve the response rates when combined with different cytotoxic agents, the majority of subsequent reports, including recent randomized studies, did not show a significant benefit stemming from TAM addition to various single-agent or multi-agent combinations. Only one controlled trial showed a significant improvement in both response rate and survival for patients receiving dacarbazine plus TAM, an effect primarily noted in women, and confirmatory studies have not been reported. From a biological standpoint, why the activity of this poorly effective single-agent is potentiated when given in combination with some cytotoxic agents is not clearly understood, although preclinical and clinical experiences support a possible synergistic effect of TAM combined with cisplatin, particularly when the former is added at high doses. Of major interest is a body of experimental studies producing confirmatory data that induction of apoptosis, probably through the inhibition of protein kinase C, as well angiogenesis inhibition, at least in part mediated by TGF-beta stimulation, are alternative ways through which TAM suppresses tumor cell growth, independently of the expression of estrogen receptors. These findings also provide a model and rationale for combining TAM with agents which are able to modify cell biology in melanoma. The investigation on TAM-containing biological combinations appears to be a promising avenue to be explored in the near future. To this end, clinical research should incorporate biological studies to allow the selection of subgroups of patients who are most likely to benefit from TAM-based treatment.