Breast cancer survival among Japanese individuals and US residents of Japanese and other origins: a comparative registry-based study

Rin Ogiya, Naoki Niikura, Hiraku Kumamaru, Yoshinori Takeuchi, Takuho Okamura, Takayuki Kinoshita, Kenjiro Aogi, Keisei Anan, Kotaro Iijima, Takanori Ishida, Takayuki Iwamoto, Masaaki Kawai, Yasuyuki Kojima, Takashi Sakatani, Yasuaki Sagara, Naoki Hayashi, Hideji Masuoka, Masayuki Yoshida, Hiroaki Miyata, Hitoshi TsudaShigeru Imoto, Hiromitsu Jinno

Research output: Contribution to journalArticlepeer-review


Background: Breast cancer survival outcomes vary across different ethnic groups. We clarified the differences in clinicopathological and survival characteristics of breast cancer among Japanese, US residents with Japanese origin (USJ), and US residents with other origins (USO). Method: Using Surveillance, Epidemiology, and End Results (SEER) 18 dataset and Japanese Breast Cancer Society (JBCS) registry, we included patients first diagnosed with breast cancer between 2004 and 2015. We categorized the patients into three groups based on the database and the recorded ethnicity: Japanese (all those from the JBCS registry), USJ (those from SEER with ethnicity: Japanese), and USO (those from SEER with ethnicity other than Japanese). Excluding patients diagnosed after 2012, stage 0, and 4 patients, we examined the overall survival (OS) and breast cancer-specific survival (BCSS) using the Kaplan–Meier method and Cox proportional hazards models, adjusting for age, sex, cancer stage, and hormone receptor (HR) status. Results: We identified 7362 USJ, 701,751 USO, and 503,013 Japanese breast cancer patients. The proportion of HR-positive breast cancer was the highest among USJ (71%). OS was significantly longer among Japanese and USJ than USO (Hazard ratio 0.46; 95% Confidence Interval [CI] 0.45–0.47 for Japanese and 0.66 [95% CI 0.59–0.74] for USJ) after adjusting for baseline covariates. BCSS was also significantly higher in the two groups (HR 0.53 [95% CI 0.51–0.55] for Japanese and 0.53 [95% CI 0.52–0.74] for USJ). Conclusions: In stage I–III breast cancer, Japanese and US residents with Japanese origin experienced significantly longer survival than US residents with non-Japanese origins.

Original languageEnglish
Pages (from-to)585-596
Number of pages12
JournalBreast Cancer Research and Treatment
Issue number2
Publication statusPublished - 2020 Nov 1


  • Breast neoplasms
  • Ethnic groups
  • Japan
  • Survival analysis
  • United states

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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