Dear Editor,

I wish to congratulate Niikura and colleagues for their article [1] in which they retrospectively evaluated the data of patients diagnosed with HER2-positive metastatic breast cancer who received trastuzumab for more than 2 years as the first-line treatment. They reported that some patients showed no evidence of disease after the interruption of trastuzumab therapy. As authors also stated that decision to discontinuation of maintenance, trastuzumab in this patient population is very critical issue. Favorable characteristics patients and tumor should be determined before stopping trastuzumab maintenance treatment. A subgroup of patients with HER2-positive metastatic breast cancer, especially those with hormone receptor negative and truly HER2-enriched subtype and those with a structurally intact HER2 receptor who are expected be more sensitive to trastuzumab might not be good candidates for discontinuation of trastuzumab. Some case reports in the literature describe the rapid onset of symptoms soon after cessation of trastuzumab which supports the theory that the withdrawal of trastuzumab might have altered the biology of the disease and its complex interactions with the host. The objective efficacy of prolonged maintenance of trastuzumab compared with observation in HER2-positive patients achieving complete response to first-line treatment should be tested in randomized trials. However, the decision of whether trastuzumab should be discontinued or not in such patients remains strongly controversial [2, 3].