Prognosis of asymptomatic versus symptomatic metastatic breast cancer: a multicenter retrospective study

In Japan, asymptomatic metastatic breast cancer (MBC) is often detected using tumor markers or imaging tests. We aimed to investigate differences in clinicopathological features, prognosis, and treatment between asymptomatic and symptomatic MBCs. Patients with MBC were retrospectively divided into asymptomatic and symptomatic groups to compare their prognosis by breast cancer subtype: luminal, human epidermal growth factor receptor 2 positive, and triple negative. Of 204 patients with MBC (114 asymptomatic, 90 symptomatic), the symptomatic group had a higher frequency of multiple metastatic sites and TN subtype. All cohorts in the asymptomatic group tended to or had longer post-recurrence survival (PRS) than those in the symptomatic group. In contrast, all cohorts and TN patients in the asymptomatic group tended to have or had longer overall survival (OS) than those in the symptomatic group, although no significant difference was observed in the luminal and HER2 subtypes. In the multivariate analysis, TN, recurrence-free survival, multiple metastatic sites, and symptomatic MBC were independently predictive of PRS. Regarding the luminal subtype, the asymptomatic group had longer chemotherapy duration than the symptomatic group, with no significant difference in OS between the groups. Asymptomatic and symptomatic MBCs differ in terms of subtypes and prognosis, and whether they require different treatment strategies for each subtype warrants further investigation.