An Overview of the Treatment Efficacy and Side Effect Profile of Pharmacological Therapies in Asian Patients with Breast Cancer

Abstract

Breast cancer (BC) among Asians accounts for ~ 40% of the global BC burden. Differences in BC risk, presentation, tumor biology, and response to treatment exist between Asian and non-Asian patients; however, Asian patients are often underrepresented in clinical trials. This narrative review summarizes the efficacy and safety of pharmacological therapies for BC in Asian populations, with a focus on outcomes in Asian versus non-Asian patients treated with chemotherapy, hormone therapy, anti-human epidermal growth factor receptor-2 targeted therapies, cyclin-dependent kinase 4/6 (CDK4/6) inhibitors, mammalian target of rapamycin inhibitors, bone-targeted therapies, poly-ADP ribose polymerase, phosphoinositide 3-kinase, and checkpoint inhibitors. While most therapies have demonstrated comparable efficacy and safety in Asian and non-Asian patients with BC, differences that are largely attributed to pharmacogenetic variations between populations exist. Pharmacogenetic differences may contribute to a reduced clinical benefit of tamoxifen, whereas improved clinical outcomes have been reported with tyrosine kinase inhibitors and CDK4/6 inhibitors in Asian versus non-Asian patients with BC. In particular, Asian patients have an increased incidence of hematological toxicities, including neutropenia, although adverse events can be effectively managed using dose adjustments. Recent trials with CDK4/6 inhibitors have increased efforts to include Asians within study subsets. Future clinical trials enrolling higher numbers of Asian patients, and an increased understanding of differences in patient and tumor genetics between Asians and non-Asians, have the potential to incrementally improve the management of BC in Asian patients.

Adjuvant olaparib in the subset of patients from Japan with BRCA1- or BRCA2-mutated high-risk early breast cancer from the phase 3 OlympiA trial

“…While there was a slightly higher incidence of Grade ≥3 AEs in patients receiving olaparib in the subset from Japan than in the global OlympiA population, the number of patients requiring permanent discontinuation of treatment due to AEs was similar between populations. Hematological toxicities occurred at a slightly higher rate in the subset of patients from Japan and are also more common in Asian patients than non-Asian patients following the administration of CT and targeted therapies for breast cancer treatment [ 9 ]. Hematological AEs can generally be managed using an effective dose adjustment strategy [ 9 ], which could further reduce the already low number of patients requiring permanent discontinuation of study treatment due to AEs.…”

“…Hematological toxicities occurred at a slightly higher rate in the subset of patients from Japan and are also more common in Asian patients than non-Asian patients following the administration of CT and targeted therapies for breast cancer treatment [ 9 ]. Hematological AEs can generally be managed using an effective dose adjustment strategy [ 9 ], which could further reduce the already low number of patients requiring permanent discontinuation of study treatment due to AEs. AML and MDS were considered AEs of special interest in the OlympiA trial.…”

The Feasibility of Omission of Postoperative Radiotherapy in Japanese Patients With Early Breast Cancer Treated With Breast-Conserving Surgery

“…For example, the PRIME II trial on BCS with or without irradiation demonstrated the safety of the omission of PORT in women ≥65 years of age with T1 or T2 tumors (≤3 cm) and node-negative, estrogen receptor (ER)-positive breast cancer [ 6 ]. However, such evidence is limited in non-Asian cohorts, and Asian and non-Asian people differ in the effectiveness and toxicity of systemic therapy [ 14 ].…”

The Feasibility of Omitting Postoperative Radiotherapy in Japanese Patients With Ductal Carcinoma In Situ of Breast Treated With Breast-Conserving Surgery

“…Although several retrospective and prospective trials have been performed in Western countries to omit PORT, the optimal conditions for omitting PORT have not yet been established [9][10][11][12]. In addition, there is limited evidence available in Asian patients, although there are differences in the efficacy and toxicity of systemic therapy [13]. Therefore, we retrospectively reviewed our database.…”