OBJECTIVES: Breast cancer (BC) is the most common cancer affecting women and, despite advances in treatment, is still the leading cause of cancer death among women worldwide. Approximately 20%-25% of the women diagnosed with BC will have HER2-positive disease and those with metastatic disease (mBC) have a 5-year life expectancy of only 24%.  Recently, pertuzumab (P) was approved as a new therapeutical option for first line HER2-positive mBC in Brazil. This study aims to define the proportion of BC patients that would be eligible for pertuzumab+trastuzumab+chemotherapy (P+T+C) combination therapy in São Paulo state by analyzing retrospectively (2000-March 2013) the Fundação Oncocentro (FOSP) cancer patient registry (Registro Hospitalar de Câncer – RHC). METHODS: Raw data of cancer cases reported from 2000-March 2013 was taken from the FOSP-RHC and mined according to the inclusion criteria of the CLEOPATRA trial. Only women with histologically/cytologically confirmed diagnosis of  BC (ICD-50) and reported TNM classification at diagnosis were included in the analysis.  P+T+C therapy eligible patients were those reported as stage IV at diagnosis (de novo mBC) or stages 0, I, II and III with evidence of progression at last tumour assessment (recurrent cases), excluding ones with evidence of central nervous system (CNS) metastasis.  Was considered that all patients in the database would test for HER2 status and positivity rate was taken from literature (25%). RESULTS: During the analysis period 59,095 BC cases with TNM classification at diagnosis were reported. 4,660 cases were considered de novo mBC and 7,378 cases were considered as recurrent. According to the positivity rate 3,010 patients would be eligible for P+T therapy which accounts for approximately 5.1% of the overall cases of BC. CONCLUSIONS: First-line HER2-positive mBC is a targeted, clearly defined and limited patient population where pertuzumab based regimen provides significant and clinically meaningful benefits in overall survival and progression-free-survival.