1025 Background: Systemic therapy is the standard care in metastatic breast cancer (BC). However, retrospective studies demonstrated survival benefits of locoregional and systemic (combination) therapy in oligometastatic BC. To clarify it, the Federation of Asian Clinical Oncology conducted an international retrospective cohort study (OLIGO-BC1) (UMIN No.000030047). Methods: Oligometastatic BC patients diagnosed from 2007 to 2012 were registered. “Oligometastases” is defined as low volume metastatic disease with limited number and size of metastatic lesions up to five and not necessarily in the same organ by the ABC guidelines. Overall survival (OS) from the diagnosis of oligometastases was the primary endpoint and compared between combination and systemic therapy using a log-rank test. Assuming the 5-year OS of 50% and 40%, respectively, 698 patients were required to achieve 80% power to detect the superiority of combination therapy, at a two-sided significance level. A multivariable Cox regression model with stratification by country was performed to estimate hazard ratio (HR) for therapy and other risk factors. Results: While 1,262 cases had been registered from February 2018 to May 2019, 1,200 remained for analysis after exclusion of unavailable cases. Among them, 573, 529 and 98 cases were registered from China, Japan and Korea, respectively. Luminal BC was recorded in 526 cases (44%), luminal-HER2 BC in 189 (16%), HER2 BC in 154 (13%), triple-negative BC in 166 (14%) and others in 165 (13%). One oligometastatic BC was found in 578 cases, 2 in 289, 3 in 154, 4 in 102 and 5 in 77. Bone metastases were recorded in 301 cases, visceral metastases in 387, locoregional recurrence in 25, local recurrence in 83 and multiple metastatic sites in 404. Combination therapy was performed in 595 cases and systemic therapy in 404. At median follow-up of 4.9 years, 5-year OS was 59.6% and 41.9%, respectively (p < 0.01). An adjusted HR was 0.61 (95% CI: 0.51, 0.74). Type of systemic therapy, younger age, ECOG performance status 0, stage I BC, non-triple negative subtype, fewer metastatic sites, local recurrence and longer disease-free interval were significantly favorable prognostic factors. Discussions: Oligometastatic BC under some conditions seems to be curable. Taken together with recent molecular targeted therapy, locoregional therapy will be advantageous to conquer it. Conclusions: Combination therapy is a promising strategy for patients with oligometastatic BC.
Gene Expression Profiling for Diagnosis of Triple-Negative Breast Cancer: A Multicenter, Retrospective Cohort Study
