Association of physical weight statuses defined by body mass index (BMI) with molecular subtypes of premenopausal breast cancer: a systematic review and meta-analysis

Background and purpose The association between overweight/obesity and postmenopausal breast cancer has been proven. However, uncertainty exists regarding the association between physical weight statuses and premenopausal breast cancer subtypes. This study aimed to explore the association of body weight statuses with molecular subtypes of premenopausal breast cancer. Method A systematic search of Medline, PubMed, Embase, and Web of Science was performed. The Newcastle–Ottawa Scale (NOS) and the Joanna Briggs Institute (JBI) Critical Appraisal tools were used to evaluate the quality of the literature. STATA and R software were used to analyze the extracted data. Result The meta-analysis included 35 observational studies with a total of 41,049 premenopausal breast cancer patients. The study showed that the proportion of underweight patients was 4.8% (95% CI = 3.9–5.8%, P = 0.01), overweight was 29% (95%CI = 27.1–30.9%, P < 0.01), obesity was 17.8% (95% CI = 14.9–21.2%, P < 0.0001), and normal weight was 51.6% (95% CI = 46.7–56.5%, P < 0.0001). The pooled results showed that in comparison to the normal weight group, being physically underweight is related to a 1.44-fold risk (OR = 1.44, 95%CI = 1.28–1.63, P < 0.0001) of HER2 + breast cancer. Overweight is related to a 1.16-fold risk (OR = 1.16, 95%CI = 1.06–1.26, P = 0.002) of TNBC and a 16% lower risk (OR = 0.84, 95%CI = 0.75–0.93, P = 0.001) of ER + breast cancer. When compared to underweight/normal weight populations, both overweight (OR = 0.74, 95%CI = 0.56–0.97, P = 0.032) and obesity (OR = 0.70, 95%CI = 0.50–0.98, P = 0.037) can reduce the risk of ER + PR + breast cancer. Conclusion In the premenopausal breast cancer population, the distribution of patients’ numbers with different weight statuses was significantly distinct among the various breast cancer subtypes. Additionally, the associations between physical weight statuses and the risk of premenopausal breast cancer subtypes are divergent.