To the Editor,

I want to congratulate Galli et al. by for their article [1] in which they analyzed the characteristics and outcome of metastatic breast cancer (MBC) patients achieving complete response (CR). They reported that durable CRs can occur after systemic therapy alone or after combined systemic and local treatments. In their study, the authors did not evaluate disease-free interval (DFI) as a factor that may affect CR in MBC. Longer DFI is a well-known positive prognostic factor and characteristic of more indolent underlying disease biology. In one study, the HR+/HER2− and HER2+ subgroups with relapsed MBC and DFI more than 5 years experienced similar median overall survival to those with de novo MBC [2]. Therefore, MBC patients with longer DFI are expected to show higher CR.