Systemic therapies for operable breast cancer patients have improved outcomes and have thus become standard treatments. Recently, new molecular target drugs and regimens are being developed based on the predicted sensitivity for specific breast cancer histological types. Systemic therapy is selected according to recurrence risk, with the treatment for low-risk patients being de-escalated, while high-risk patients receive aggressive systemic treatment with an adequate dose and duration. Neoadjuvant systemic therapy has a different aim. The efficacy of systemic therapies, based on the sensitivities to drugs, is supported by improvements in the rate of breast-conserving therapy. The response to neoadjuvant systemic therapy is the most important factor for predicting outcomes and selecting the optimal adjuvant therapy. Novel biological markers unique to individual patients allow appropriate targeted therapy, which can achieve optimal efficacy.

This trial is being conducted to confirm the superiority, in terms of overall survival, of primary tumour resection plus systemic therapy to systemic therapy alone in patients with Stage IV breast cancer who are not refractory to primary systemic therapy. The inclusion criteria for the study are as follows: untreated patients with histologically confirmed invasive breast cancer with one or more measurable metastatic lesions diagnosed by radiological examination. All patients receive primary systemic therapy according to the estrogen receptor and human epidermal growth factor receptor type-2 status of the primary breast cancer after the first registration. After 3 months, the patients without disease progression are randomized to the primary tumour resection plus systemic therapy arm or the systemic therapy alone arm. The primary endpoint is the overall survival, and the secondary endpoints are proportion of patients without tumour progression at the metastatic sites, yearly local recurrence-free survival, proportion of local ulcer/local bleeding, yearly primary tumour resection-free survival, adverse events of chemotherapy, operative morbidity and serious adverse events. The patient recruitment was commenced in May 2011. Enrolment of 410 patients for randomization is planned over a 5 year recruitment period. We hereby report the details of the study.

The eighth editions of the primary tumor, lymph node and metastasis classifications for breast cancer issued by the American Joint Commission of Cancer and the Union for International Cancer Control were revised in 2017. The major change made by the American Joint Commission of Cancer is to incorporate biological factors such as estrogen and progesterone receptor, human epidermal growth factor receptor 2, histological grade and multigene prognostic assays, into the staging system. Tumor biomarkers and low recurrence scores confirmed by multigene prognostic assays change the staging. Minor changes are to add the post-neoadjuvant therapy clinical and pathological classification and to define the size of tumor, lymph node and metastasis components more precisely. Little has changed in the Union for International Cancer Control. We have identified key points of change in both eighth editions of the tumor, lymph node and metastasis classifications and we discuss possible problems which may arise when they are adopted in Japanese practice, as well as future directions.

Introduction: Microtubule-associated protein tau (MAPT) inhibits the function of taxanes and high expression of MAPT decreases the sensitivity to taxanes. The relationship between estrogen receptor (ER) and MAPT in breast cancer is unclear. In this study, we examined the correlation of MAPT expression with the sensitivity of human breast cancer cells to taxanes, and the relationship between ER and MAPT. Methods: The correlation between MAPT expression and sensitivity to taxanes was investigated in 12 human breast cancer cell lines. Alterations in cellular sensitivity to taxanes were evaluated after knockdown of MAPT expression. ER expression was knocked down or stimulated in MAPT- and ER-positive cell lines to examine the relationship between ER and MAPT. The cells were also treated with hormone drugs (tamoxifen and fulvestrant) and taxanes. Results: mRNA expression of MAPT did not correlate with sensitivity to taxanes. However, expression of MAPT protein isoforms of less than 70 kDa was correlated with a low sensitivity to taxanes. Downregulation of MAPT increased cellular sensitivity to taxanes. MAPT protein expression was increased by stimulation with 17-β-estradiol or tamoxifen, but decreased by ER downregulation and by fulvestrant, an ER inhibitor. The combination of fulvestrant with taxanes had a synergistic effect, whereas tamoxifen and taxanes had an antagonistic effect. Conclusions: Expression of MAPT protein isoforms of less than 70 kDa is correlated with a low sensitivity to taxanes in breast cancer cells. ER influences MAPT expression and fulvestrant increases the sensitivity to taxanes in MAPT- and ER-positive breast cancer cells.

Compensatory activation of the signal transduction pathways is one of the major obstacles for the targeted therapy of non‐small cell lung cancer (NSCLC). Herein, we present the therapeutic strategy of combined targeted therapy against the MEK and phosphoinositide‐3 kinase (PI3K) pathways for acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in NSCLC. We investigated the efficacy of combined trametinib plus taselisib therapy using experimentally established EGFR‐TKI‐resistant NSCLC cell lines. The results showed that the feedback loop between MEK/ERK and PI3K/AKT pathways had developed in several resistant cell lines, which caused the resistance to single‐agent treatment with either inhibitor alone. Meanwhile, the combined therapy successfully regulated the compensatory activation of the key intracellular signals and synergistically inhibited the cell growth of those cells in vitro and in vivo. The resistance mechanisms for which the dual kinase inhibitor therapy proved effective included (MET) mesenchymal‐epithelial transition factor amplification, induction of epithelial‐to‐mesenchymal transition (EMT) and EGFR T790M mutation. In further analysis, the combination therapy induced the phosphorylation of p38 MAPK signaling, leading to the activation of apoptosis cascade. Additionally, long‐term treatment with the combination therapy induced the conversion from EMT to mesenchymal‐to‐epithelial transition in the resistant cell line harboring EMT features, restoring the sensitivity to EGFR‐TKI. In conclusion, our results indicate that the combined therapy using MEK and PI3K inhibitors is a potent therapeutic strategy for NSCLC with the acquired resistance to EGFR‐TKIs.