Prospective construction and validation of a prognostic score to identify patients who benefit from third-line chemotherapy for metastatic breast cancer in terms of overall survival: the METAL3 Study.

Metastatic breast cancer (MBC) is an incurable disease and represents a complex therapeutic challenge for oncologists. Despite the possibility of prescribing new agents such as tailored therapy, cytotoxic chemotherapy and hormone therapy remain the major treatments for MBC. Several lines of chemotherapy can be proposed for these patients, but beyond the second-line, evidence of effectiveness is lacking and such treatment has important associated toxicity affecting quality of life (QoL). Prospective data on third-line chemotherapy is very poor. There is no recent retrospective data and it mainly includes single-centre experiences. Moreover, prognostic parameters considered in these retrospective studies are limited to clinico-pathological factors. Previous reports don't evaluate prognostic impact of circulating tumour cells (CTC) and baseline QoL. METAL3 METAstatic Line 3 is a prospective, multicentric trial designed to prospectively construct a prognostic score (including selected clinico-pathological factors, CTC and baseline QoL) to identify patients who benefit from third-line chemotherapy for MBC in terms of overall survival (training cohort). Score will then be validated with another cohort (validation cohort). The aim of this paper is to review literature data on third-line chemotherapy for MBC and to describe in detail our prospective study. We hope that this prognostic score could be used by physicians to develop new therapeutic strategies when there will be limited benefit of third-line chemotherapy; this score will also help to improve patient information on their outcome.