[Clinical Impact of First Metastasis Sites and Subtypes in the Outcome of Brain Metastases of Breast Cancer].

Brain metastasis(BM)is the final stage of metastatic breast cancer(MBC), but its course and outcomes after the first metastasis(FM)to various sites are not fully clarified. Furthermore, the survival of patients with BM appears to be improving with the recent development in MBC control according to the subtype analysis. The present study included 35 patients with BM between 2008 and 2018, and was designed to clarify the effects of the FM sites and subtypes on the outcome of these patients. Subtypes included 8 Luminal(L), 8 L-HER2+(LH), 8 HER2(H), and 11 triple-negative(TN)types, and FM sites included 14 lungs or pleurae, 4 livers, 4 brains, 4 bones, and 9 local or lymph node(LN)metastases. The median interval between FM and BM(IFB)was 33 months(M)for overall patients; 50M for LH, 37M for L, 22M for H, and 19M for TN (p=0.0463); and 24M for the high risk(HR)FM(lung, pleura, liver)and 47M for the low risk(LR)FM group(bone, local, LN)(p=0.0385). The median overall survival(OS)after BM diagnosis was 13M for overall patients; 27M for LH, 13M for H, 10M for L, and 5M for TN(p=0.0112). There were no significant differences in the OS after BM diagnosis between HR FM and LR FM patients. Multivariate analyses for OS after BM revealed that patients with HER2(+)and estrogen receptor(+) tumors had a significantly better survival(risk ratio[RR]=0.644, p=0.0413; RR=0.290, p=0.0251, respectively). Three patients are surviving longer than 10 years after BM, including 2 with L-type and 1 with LH-type tumors, and their FM sites were 1 local, 1 brain, and 1 liver. The present study indicated that subtypes and FM site(HR or LR)had significant impact on the clinical course and prognosis of patients with BM. Focusing on the subtypes and FM site can improve the early detection and treatment results of BM.