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Review
May 16, 2019

Insights Into Breast Cancer in the East vs the West: A Review

Author Affiliations
  • 1Division of Medical Oncology, National Cancer Centre Singapore, Singapore
  • 2Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan
  • 3Department of Breast and Medical Oncology, National Cancer Center Hospital, Tokyo, Japan
  • 4Breast Division, Department of Surgery, Samsung Medical Center, Seoul, South Korea
  • 5Department of Radiology, Samsung Medical Center, Seoul, South Korea
  • 6Division of Hematology-Oncology, Department of Medicine, Samsung Medical Center, Seoul, South Korea
  • 7Department of Breast Surgery, Fudan University Shanghai Cancer Center, Shanghai, China
  • 8Breast Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan
  • 9Department of Haematology-Oncology, National University Cancer Institute, Singapore
  • 10Cancer Science Institute, National University of Singapore, Singapore
JAMA Oncol. 2019;5(10):1489-1496. doi:10.1001/jamaoncol.2019.0620
Key Points

Question  What are the differences in breast cancer between the East and the West?

Findings  In this review of breast cancer in East Asia, a greater proportion of breast cancers occur in younger women, and a higher frequency of luminal B subtype and TP53 mutations and a more immune-active microenvironment have been reported than in the West. The spectra of germline mutations and single-nucleotide polymorphisms contributing to breast cancer risk vary with ethnicity. Differences in tolerability of certain cytotoxic and targeted agents and other phenotypic characteristics may also influence treatment and imaging considerations.

Meaning  Further research on ethnic diversity related to breast cancer is needed to help refine prevention, diagnostic, and management strategies.

Abstract

Importance  During the past few decades, the incidence of breast cancer (BC) has been increasing rapidly in East Asia, and BC is currently the most common cancer in several countries. The rising incidence is likely related to changing lifestyle and environmental factors in addition to the increase in early diagnosis with BC awareness and screening. The understanding and management of BC are generally based on research and data from the West. However, emerging differences in BC epidemiology and tumor and host biology in Asian populations may be clinically relevant.

Observations  A higher proportion of premenopausal BCs occur in Asia, although this factor is possibly an age-cohort effect. Although the relative frequencies of different immunohistochemical subtypes of BC may be similar between the East and West, the higher prevalence of luminal B subtypes with more frequent mutations in TP53 may be confounded by disparities in early detection. In addition, Asian BCs appear to harbor a more immune-active microenvironment than BCs in the West. The spectra of germline mutations in BC predisposition genes and single-nucleotide polymorphisms contributing to BC risk vary with ethnicity as well. Differences in tolerability of certain cytotoxic and targeted agents used in BC treatment may be associated with pharmacogenomic factors, whereas the lower body mass of the average woman in East Asia may contribute to higher toxicities from drugs administered at fixed doses. Phenotypic characteristics, such as lower breast volume, may influence the type of surgery performed in East Asian women. On the other hand, increased breast density may affect the sensitivity of mammography in detecting BCs, limiting the benefits of screening mammography.

Conclusions and Relevance  Breast cancer has become a major health problem in Asia. The inclusion of more women from Asia in clinical trials and epidemiologic and translational studies may help unravel the interethnic heterogeneity of BCs and elucidate the complex interplay between environmental and intrinsic factors in its pathogenesis. These insights may help to refine prevention, diagnosis, and management strategies for BC in the setting of ethnic diversity.

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