Preoperative Systemic Therapy Versus Upfront Surgery in HER2 Positive Early Breast Cancer: a Prospective Nested Case-control Study in Real World

Patients with a diagnosis of HER2 positive early invasive breast cancer (cT1-3N0-1M0), from January 2012 to December 2014 were identified and enrolled continuously. The conditions of HER2-positive expression of primary breast cancer were defined as follows: HER2 3+ by immunohistochemical (IHC) method or HER2 2+ by IHC with a further positive result by fluorescence in situ hybridization (FISH). According to the real upfront treatment, all eligible patients were classified as PST group and surgery group. All the patients accepted standard one-year trastuzumab as anti-HER2 treatment combined with chemotherapy. In the PST group, the effect was evaluated according to RECIST1.1 every two cycles, the patients with clinical complete response (cCR) or partial response (PR) would receive the whole course of chemotherapy, those with stable disease (SD) or progressive disease (PD) would receive surgery promptly. After surgery, all patients underwent irradiation and endocrine therapies if necessary. The pCR was defined as the absence of infiltrating residual invasive disease in the breast and axillary nodes. For those non-pCR patients after PST, intensive adjuvant chemotherapy was not routine treatment except patients with progressive disease.The primary endpoint was DFS defined as the time from enrollment to local, regional, or distant recurrences; the occurrence of contralateral breast cancer; or death without evidence of breast cancer. Patients suffered disease progress becoming inoperable before surgery were counted as local treatment failures. The second endpoint was OS defined as the time from study entry to death from any cause. All the endpoints were compared between PST group and upfront surgery group, also further analysis according to pathological response status stratified in PST group.