Cancer cells induce proliferation and local accumulation of immunosuppressive cells, such as FOXP3-positive cells known as regulatory T cells (Tregs), leading to tumor-induced immune tolerance. Although cancer chemotherapy is usually considered immunosuppressive, some chemotherapeutic agents activate an anticancer immune response. Therefore, we postulated that the number of tumor-infiltrating FOXP3-positive cells during primary systemic chemotherapy (PSC) correlates with therapeutic outcomes in patients with breast cancer. Between September 2000 and January 2005, we examined 93 patients with breast cancer diagnosed by core-needle biopsy and treated with PSC. Core-needle biopsy (CNB) and surgical resected specimens were stained with a FOXP3 mouse monoclonal antibody to compare the numbers of FOXP3-positive cells in the tumors before and after PSC. A median cut-off value of >16.3/high power field (HPF) and >6.6/HPF defined high numbers of Tregs in CNB and in surgical specimens, respectively. We then assigned the patients into 4 groups (HH, high number of FOXP3-positive cells in both CNB and surgical specimen; LL, low number in both specimens; HL, high in CNB and low in the surgical specimen; LH, low in CNB and high in surgical specimen). Lymph vessel invasion-positive, clinically non-responder and ER-negative tumors contained significantly more FOXP3-positive cells after PSC (p=0.04, p=0.03 and p=0.04, respectively). Prognosis was better among patients with low numbers than high numbers of FOXP3-positive cells both in CNB and in surgically resected specimens. In multivariate analysis, LL group demonstrated significantly better recurrence-free survival with risk ratio of 5.81 (95%CI, 1.09-107.5; p=0.04) rather than that of non-LL group (LH, HL and HH). These findings suggest that the number of FOXP3-positive cells identified during PSC represents a promising predictive factor that might also be an important therapeutic target for breast cancer.

Objective: Bone marrow (BM)-derived endothelial progenitor cells (EPC) play an important role in neovascularization and tumor growth. It has been reported that docetaxel and paclitaxel inhibit angiogenesis, but the effect of docetaxel and paclitaxel on EPC-induced neovascularization has not been examined. We aimed to clarify the cytotoxic and inhibitory effects of these drugs on EPC. Methods: The effects of drugs on growth, tube formation, and migration of EPC were analyzed in vitro using a rat BM-derived EPC cell line (TR-BME). Fluorescence-labeled TR-BME cells were injected into tumor-bearing rats and accumulation at the tumor site was analyzed by fluorescence-activated cell sorting (FACS). Results: In in vitro cytotoxicity assays of these drugs in TR-BME, rat endothelial cell line TR-BBB and rat tumor cell line Walker 256, the IC₅₀ values for TR-BME were higher than those for TR-BBB or Walker 256. Both drugs inhibited tube formation and migration of TR-BME at lower concentrations than the cytotoxic IC₅₀. In vivo studies showed that a low dose of both drugs inhibited EPC accumulation at the tumor site in tumor-bearing rats, as determined by FACS, and caused a decrease in microvessel density. Conclusion: Docetaxel and paclitaxel directly inhibited EPC-initiated vasculogenesis at low (non-cytotoxic) concentrations, causing suppression of tumor growth.

We aimed to confirm the efficacy and safety of the oral histone deacetylase inhibitor entinostat in Japanese patients with hormone receptor-positive advanced/recurrent breast cancer and to explore potential biomarkers. This phase II, double-blind, randomized, placebo-controlled trial (ClinicalTrials.gov; NCT03291886) was conducted at 28 Japanese sites (September 2017–July 2020; interim analysis cutoff: April 2019). Patients with progression/relapse following non-steroidal aromatase inhibitors were randomized 1:1 to entinostat (5 mg/week) or placebo, plus exemestane (25 mg/day). Primary endpoint was progression-free survival; secondary endpoints included overall survival and safety. Exploratory biomarker outcomes included lysine acetylation, immune cell profiles, estrogen receptor 1 mutations and plasma chemokines. Of 133 randomized patients, 131 (65 entinostat, 66 placebo) who received study drug were analyzed. Median (95% confidence interval) progression-free survival was 5.8 (3.2–7.8) months for entinostat and 3.3 (3.1–5.8) months for placebo (hazard ratio [95% confidence interval]: 0.75 [0.50 − 1.14]; P = 0.189). Median overall survival was not reached in either group. Entinostat tended to prolong progression-free survival in patients aged ≥65 years, not endocrine resistant, or with estrogen receptor 1 Y537S mutation. Candidate biomarkers of efficacy (progression-free survival) included lysine acetylation in CD3+ cells, plasma interferon gamma-induced protein 10, dendritic cell CD86 expression, and CD4+ cell expression of human leukocyte antigen-DR and inducible T-cell co-stimulator. Safety was similar to non-Japanese populations; however, seven entinostat-treated patients (10.8%) had reversible lung injury. In Japanese patients, the safety of entinostat plus exemestane was acceptable and progression-free survival was prolonged, although not significantly. Exploratory analyses identified potential biomarkers, including lysine acetylation, of efficacy.

Due to the increase in the number of early-stage breast cancer patients, there is growing interest in minimally invasive local therapies for breast cancer. Radiofrequency ablation (RFA) therapy is one of the most promising minimally invasive treatments. The Radiofrequency Ablation Therapy for Early Breast Cancer as Local Therapy (RAFAELO) study, a multicenter collaborative study that aims to validate the efficacy and safety of RFA and to standardize its use for early-stage breast cancer, was conducted under the Advanced Medical Care B system in 2013. This study enrolled the expected number of patients in November 2017; moreover, it is currently in the follow-up period. Some patients with early-stage breast cancer who are eligible for RFA could not receive the RFA treatment, as it is still not covered by insurance. Therefore, the Patients Offer Radiofrequency Ablation Therapy for Early Breast Cancer as Local Therapy (PO-RAFAELO) study under the Patient-proposed Health Services (PPHS) was proposed and approved in March 2019. The PPHS is a system that allows patients to receive prompt access to advanced medical care at a medical facility close to them, starting with their request. This system is considered a part of the specific and special medical coverage. The PO-RAFAELO study is the only study in the surgical field utilizing the PPHS, aiming to help in achieving regulatory approval and insurance coverage of RFA for breast cancer. As of January 2023, 120 patients have undergone RFA using the PPHS and no grade 3 or higher early adverse events have occurred. A certain number of patients with early-stage breast cancer prefer nonsurgical treatment, and it is important to provide information regarding the availability of RFA for early-stage breast cancer under the PPHS. Trial registration: registered with Japan Registry of Clinical Trial on March 06, 2019 (Trial ID: jRCTs032180187).

Purpose: The randomized phase 2 Neo-peaks study examined usefulness of neoadjuvant trastuzumab emtansine + pertuzumab (T-DM1 + P) following docetaxel + carboplatin + trastuzumab + pertuzumab (TCbHP) as compared with the standard TCbHP regimen. We previously reported that pCR rate after neoadjuvant therapy tended to be higher with TCbHP followed by T-DM1 + P. We conducted an exploratory analysis of prognosis 5 years after surgery. Methods: Neoadjuvant treatment with TCbHP (6 cycles; group A), TCbHP (4 cycles) followed by T-DM1 + P (4 cycles; group B), and T-DM1 + P (4 cycles; group C, + 2 cycles in responders) were compared. Group C non-responders after 4 cycles were switched to an anthracycline-based regimen. We evaluated 5-year disease-free survival (DFS), distant DFS (DDFS), and overall survival (OS). Results: Data from 203 patients (50, 52, and 101 in groups A–C, respectively) were analyzed. No significant intergroup differences were found for DFS, DDFS, or OS. The 5-year DFS rates (95% CI) were 91.8% (79.6–96.8%), 92.3% (80.8–97.0%), and 88.0% (79.9–93.0%) in groups A–C, respectively. TCbHP followed by T-DM1 + P and T-DM1 + P with response-guided addition of anthracycline therapy resulted in similar long-term prognosis to that of TCbHP. Conclusions: In patients who achieved pCR after neoadjuvant therapy with T-DM1 + P, omission of adjuvant anthracycline may be considered, whereas treatment should be adjusted for non-pCR patients with residual disease. T-DM1 + P with response-guided treatment adjustment may be useful for minimizing toxicity. Trial registration number and date of registration: UMIN-CTR, UMIN000014649, prospectively registered July 25, 2014. Some of the study results were presented as a Mini Oral session at the ESMO Breast Cancer 2023 (Berlin, Germany, 11–13 May 2023).