Ann Surg Treat Res.  2022 Sep;103(3):119-128. 10.4174/astr.2022.103.3.119.

Clinicopathological features and prognosis associated with breast cancer laterality: a nationwide study from the Korean Breast Cancer Society

  • 1Department of Surgery, Daejeon St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
  • 2Department of Surgery, Yeungnam University Medical Center, Yeungnam University College of Medicine, Daegu, Korea
  • 3Department of Surgery, Jeonbuk National University Medical School, Jeonju, Korea
  • 4Department of Surgery, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea
  • 5Department of Surgery, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
  • 6Department of Surgery, Incheon St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
  • 7Breast-Thyroid Center, Saegyaero Hospital, Busan, Korea


Although breast cancer is known to show a left predominance, the clinical characteristics and causes underlying this finding remain unclear. In addition, no related studies on breast cancer laterality have been conducted in patients with breast cancer in Korea. Therefore, we aimed to analyze differences in breast cancer laterality and the associated clinicopathological characteristics and prognosis among Korean patients with breast cancer.
We conducted a retrospective analysis using large-scale data on clinicopathological factors and prognosis differences related to breast cancer laterality from the Korean Breast Cancer Society Registration system. The left-to-right ratio (LRR) of breast cancer was calculated through binomial distribution, and factors related to breast cancer laterality were identified through logistic regression analysis. In addition, the differences in the survival rates for left and right breast cancers were analyzed using the Kaplan-Meier method and Cox proportional hazards model.
In 171,500 patients, the LRR was 1.031 (95% confidence interval, 1.022–1.041; P < 0.001). Multivariate analysis showed that the ratio of left breast cancer was related to age, body mass index (BMI), location, and human epidermal growth factor receptor 2 (HER2) status. The survival rate of patients with left and right breast cancers showed no significant difference.
A large-scale analysis revealed a left predominance in breast cancer laterality in Korean patients. Over time, this predominance gradually decreased. Age, BMI, location, and HER2 status affected breast cancer laterality. However, while left breast cancer showed relatively aggressive characteristics, it was not associated with a difference in the survival rate.


Epidemiology; Survival; Unilateral breast neoplasms


  • Fig. 1 Linear regression models of the unilateral breast cancer laterality with continuous variables, such as (A) year of operation, (B) age, (C) body mass index, and (D) Ki-67. The black dots and lines indicate the ratios of left breast cancers to right breast cancers and their 95% confidence intervals. The slopes of the gray lines indicate the correlation between breast cancer laterality and the continuous variables.

  • Fig. 2 Unilateral breast cancer laterality distributions according to the factors. CI, confidence interval; BMI, body mass index; ER, estrogen receptor; PR, progesterone receptor; HER2, human epidermal growth factor receptor 2; BCS, breast-conserving surgery; SLNB, sentinel lymph node biopsy; AD, axillary dissection.

  • Fig. 3 (A) Breast cancer-specific survival and (B) overall survival curves of left and right breast cancer groups.


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