In Japan, asymptomatic metastatic breast cancer (MBC) is often detected using any tumor marker or imaging tests. We aimed to determine whether differences in clinicopathological features, subtypes, prognosis, and treatment exist between asymptomatic and symptomatic MBCs.
We performed a multicenter, retrospective analysis of patients with MBC who visited our hospitals from 2008 to 2018. Patients were divided into asymptomatic and symptomatic groups to compare their prognosis by breast cancer subtypes: luminal (hormone receptor positive/hormone receptor negative/human epidermal growth factor receptor 2 (HER2) negative), HER2 (any hormone receptor/HER2 positive), and TN (hormone receptor negative/HER2 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 and TN patients in the asymptomatic group had longer post-recurrence survival (all cohorts: p < 0.001, TN: p = 0.01) and tended to have longer overall survival (all cohorts: p = 0.09, TN: p = 0.06) than those in the symptomatic group. In contrast, for the luminal and HER2 subtypes, post-recurrence survival was higher in the asymptomatic group than in the symptomatic group (luminal: p = 0.08, HER2: p = 0.09) but without significant difference in overall survival. In the multivariate analysis, TN, recurrence-free survival, multiple metastatic sites, and symptomatic MBC were independently predictive of post-recurrence survival. Regarding the luminal subtype, the asymptomatic group had longer durations of chemotherapy than the symptomatic group, with no significant difference observed in overall survival between the groups.
Asymptomatic and symptomatic MBCs require unique treatments due to prognostic differences.