Emerging literature data are showing that a change in human epidermal growth factor receptor (HER2) status adversely affects breast cancer patient's prognosis. The aim of this study was to evaluate the prognostic impact of HER2 loss in patients with HER2-positive disease treated with neoadjuvant therapy with or without anti-HER2 agents. One hundred and seven consecutive HER2-positive patients were identified from a prospectively maintained database. The first cohort includes 40 patients treated with chemotherapy (CT) alone. The second cohort includes 67 patients treated with neoadjuvant CT plus anti-HER2 agents (trastuzumab and/or lapatinib). HER2 expression was evaluated by immunihistochemistry or fluorescence in situ hybridization on pretreatment core biopsy and on surgical specimen after therapy. The rates of pathologic complete response (pCR) and breast-conserving surgery were higher in the CT + anti-HER2 cohort. A loss of HER2 expression was observed in 40% of the patients with residual disease after CT alone versus 14.7% of the patients after CT + anti-HER2 agents (P = 0.019). Patients not achieving a pCR have a significant increase in the risk of relapse when compared with those achieving a pCR (hazard ratio [HR] 9.55, P = 0.028). Patients with HER2 loss tended to have a higher risk of relapse as comparing to patients with maintained HER2 positivity (HR 2.41, P = 0.063). The pCR is confirmed as a powerful predictor of long-term outcome. The rate of HER2 loss is higher in patients receiving neoadjuvant CT without anti-HER2 agents. HER2 status on residual disease after preoperative therapy can be helpful in selecting patients at different risk of relapse, to be included in prospective trial exploring further adjuvant therapy.

Breast cancer (BC) is the most common women cancer and cause of cancer death. Despite decades of scientific progress in BC treatments, the clinical benefit of new drugs is modest in several cases. The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway mutations are frequent in BC (20–40%) and are significant causes of aggressive tumor behavior, as well as treatment resistance. Improving knowledge of the PI3K/AKT/mTOR pathway is an urgent need. This review aims to highlight the central role of PI3K-mTORC1/C2 mutations in the different BC subtypes, in terms of clinical outcomes and treatment efficacy. The broad base of knowledge in tumor biology is a key point for personalized BC therapy in the precision medicine era.

Tumor-infiltrating lymphocytes (TILs) evaluated in primary breast cancer (BC) convey prognostic information. Limited data in the metastatic setting are available. Secondary lesions from 94 BC patients, 43 triple-negative (TN) and 51 HER2-positive, were evaluated for TILs and expression of CD8, FOXP3, and PD-L1 by immunohistochemistry. TILs levels on metastasis were generally low (median 5%) and did not differ between TN and HER2+ tumors. Younger patients showed significantly lower TILs (p = 0.002). In HER2+ patients, TILs were higher in lung metastases as compared to other sites (p = 0.038). TILs composition was different across metastatic sites: skin metastases presented higher FOXP3 (p = 0.002) and lower CD8/FOXP3 ratio (p = 0.032). Patients treated for metastatic BC prior to biopsy had lower CD8 (overall: p = 0.005, HER2+: p = 0.011, TN: p = 0.075). In TN patients, median overall survival (OS) was 11.8 and 62.9 months for patients with low and high TILs, respectively (HR 0.29, 95%CI 0.11–0.76, log-rank p = 0.008). CD8/FOXP3 ratio was also prognostic in TN patients (median OS 8.0, 13.2, and 54.0 months in 1st, 2nd and 3th tertile, log-rank p = 0.019). Both TILs and CD8/FOXP3 ratio were independent factors at multivariate analysis. Counterintuitively, in HER2+ BC, low TILs tumors showed better prognosis (median OS 53.7 vs 39.9 months in TILs low and TILs high, not statistically significant). Our findings indicate the relevance of TILs as prognostic biomarker for TNBC even in the advanced setting and provide novel hypothesis-generating data on potential sources of immune heterogeneity of metastatic BC.

Triple-negative breast cancer (TNBC) remains the poorest-prognosis breast cancer (BC) subtype. Gene expression profiling has identified at least six different triple-negative subtypes with different biology and sensitivity to therapies. The heterogeneous nature of TN tumors may justify the difficulty in treating this BC subtype. Several targeted agents have been investigated in clinical trials without demonstrating a clear survival benefit. Therefore, systemic chemotherapy remains the cornerstone of current clinical practice. Improving the knowledge of tumor biology is mandatory for patient management. In stages II and III, neoadjuvant systemic treatment is an effective option of care. The achievement of a pathological complete response represents an optimal surrogate for survival outcome as well as a test for tumor drug sensitivity. In this review, we provide a brief description of the main predictive biomarkers for tumor response to systemic treatment. Moreover, we review the treatment strategies investigated for TNBCs in neoadjuvant settings focusing on experimental drugs such as immunotherapy and poly [ADP-ribose] polymerase inhibitors that hold promise in the treatment of this aggressive disease. Therefore, the management of TNBC represents an urgent, current, unmet need in daily clinical practice. A key recommendation is to design biology-driven clinical trials wherein TNBC patients may be treated on the basis of tumor molecular profile.