Abstract P1-14-04: Overall survival in metastatic breast cancer patients in the third millennium: Results of an Italian study

BACKGROUND - Metastatic breast cancer (MBC) is a life-threatening disease. It is important to provide data about real-life MBC patients (pts) to understand the current prognostic factors. The aim of the present observational study, named COSMO (Checking Overall Survival in a MBC Observational study) is to describe the overall survival (OS) in a large cohort of MBC pts, assessing its correlation with specific prognostic factors (demographic, clinic, pathologic and biological). PATIENTS AND METHODS - The COSMO study is a multicenter, retrospective, cohort study, developed throughout the collaboration of 31 Italian oncological centers. Data about pts diagnosed as metastatic from 01/01/2000 to 31/12/2008, were collected. The association between molecular subtypes, metastatic sites, disease free interval (DFI) and OS were assessed. Pts were classified in three subgroups, based on the biological characteristics of their tumor: luminal, HER2-positive (regardless of hormone receptor) and triple negative (TN). Metastatic sites were categorized as visceral versus non-visceral disease, only bone and central nervous system (CNS) metastases. DFI was calculated from diagnosis to first relapse only for M0 pts. RESULTS - Of 3931 MBC pts enrolled in the study, 3720 were evaluable, with a median age of 61 years (interquartile range, IQR, 51-71). 1804 (62,1%) pts had a luminal disease, 691 (23,8%) HER2-positive, 410 (14.1%) TN. Median DFI was 3.2 years (IQR 1.7- 6.0). Regarding metastatic sites, pts with visceral disease were 2332 (63%); 826 (22,2%) pts had bone isolated metastases; in 306 (8,3%) pts, CNS metastases were reported. With a median follow up of 9 years (IQR 5.7-11.0) and 3098 (83.3%) recorded events, we founded a median OS of 2.8 years (95%CI: 2.7-2.9) years. OS was strictly depending from molecular subtypes with a better prognosis for HER2-positive versus luminal and TN MBC pts, median OS of 3.1 (95%CI 2.8-3.4), 3.0 (95%CI: 2.9-3.1) and 1.5 (95%CI: 1.3-1.7) years respectively (p-value 2 years show a median OS of 3 years (95% CI: 2.9 – 3.2), while those with DFI CONCLUSIONS - Molecular subtype is crucial for prognosis: HER2-positive subtype has the best prognosis, while TN subtype has the shorter OS. Having a longer DFI from diagnosis (>2 years) correlate with a better prognosis. Our study confirm that sites of metastasis affects outcome: visceral involvement correlates with poor prognosis and, particularly, pts with brain metastasis represent the worst subgroup, while pts with solely bone disease have the best prognosis. The COSMO study provides a view on the Italian landscape of MBC between 2000 and 2008, adding new insights about pts prognosis. Citation Format: La Verde N, Collova E, Blasi L, Pinotti G, Bernardo A, Bonotto M, Garrone O, Brunello A, Cavazzini MG, Bareggi C, Prochilo T, Porcu L, Moretti A, Barni S, On Behalf of COSMO Study Group. Overall survival in metastatic breast cancer patients in the third millennium: Results of an Italian study [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-14-04.