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e-Poster Display Session

11P - Genetically predicted bipolar disorder is causally associated with increased risk of breast cancer: A Mendelian randomization analysis


22 Nov 2020


e-Poster Display Session


Tumour Site

Breast Cancer


Haoxin Peng


Annals of Oncology (2020) 31 (suppl_6): S1241-S1254. 10.1016/annonc/annonc351


H. Peng, X. Wu, C. Li, W. Liang, J. He

Author affiliations

  • The First Affiliated Hospital Of Guangzhou Medical University, Guangzhou, China., Department of Thoracic Oncology and Surgery, China State Key Laboratory of Respiratory Disease & National Clinical Research Center for Respiratory Disease, 510000 - Guangzhou/CN


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Abstract 11P


Epidemiologic findings suggested that bipolar disorder (BD) may be associated with increased risk of breast cancer. However, there are few studies that comprehensively evaluate their correlation and the causal effect remains unknown. With a Mendelian randomization (MR) approach, we were able to investigate the causal relationship between genetically predicted BD and breast cancer risk.


Utilizing 6 BD-related single nucleotide polymorphisms as instrumental variables identified by the latest genome-wide association studies, we investigated the correlation between genetically predicted BD and breast cancer risk using summary statistics from the Breast Cancer Association Consortium, with a total of 122 977 cases and 105 974 controls. Study-specific estimates were summarized using inverse-variance-weighted (IVW) method. To further evaluate the pleiotropy, the weighted median and the MR-Egger regression method were implemented. Subgroup analyses according to different immunohistochemical type of breast cancer were also conducted.


MR analyses demonstrated that genetically predicted BD was causally associated with an increased risk of breast cancer (OR = 1.058; 95% CI 1.023-1.093, p < 0.001). When results were examined by immunohistochemical type, a strong association was observed between genetically predicted BD and estrogen receptor-positive (ER) breast cancer (OR = 1.048, 95%CI 1.008-1.090 p = 0.0177) rather than ER-negative breast cancer (OR = 1.026, 95%CI 0.975-1.081 p = 0.3231). Additionally, the results demonstrated the absence of the horizontal pleiotropy. Table: 11P

Mendelian randomization estimates of the associations between bipolar disorder and risk of breast cancer overall and immunohistochemical types

Outcome IVW method MR-Egger Weighted median method
OR (95% CI) P-value OR (95% CI) P-value OR (95% CI) P-value
Breast cancer overall 1.058 (1.023, 1.093) 0.0009 1.032 (0.969, 1.099) 0.3858 1.044 (1.006, 1.083) 0.0239
ER-positive breast cancer 1.048 (1.008, 1.090) 0.0177 1.004 (0.942, 1.070) 0.9118 1.030 (0.998, 1.074) 0.1622
ER-negative breast cancer 1.026 (0.975, 1.081) 0.3231 1.085 (0.986, 1.195) 0.1713 1.041 (0.978, 1.109) 0.2063


Our findings provide evidence for a causal relationship between genetically predicted BD and increased breast cancer risk, overall and among specific immunohistochemical type. Further studies are warranted to investigate the underlying mechanism.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Haoxin Peng.


China National Science Foundation (Grant No. 81871893); Key Project of Guangzhou Scientific Research Project (Grant No. 201804020030); Cultivation of Guangdong College Students' Scientific and Technological Innovation (“Climbing Program” Special Funds) (Grant No. pdjh2020a0480).


All authors have declared no conflicts of interest.

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