We read with interest “Letter to the editor: Effects of Bariatric Surgery on Cancer Risk: Evidence from Meta-analysis”. Our meta-analysis  assessed the effect of bariatric surgery on overall cancer risk by comparing cancer risk in patients who had undergone bariatric surgery and cancer risk in patients with obesity who had not undergone weight reduction surgery. We evaluated the eligible studies if all the following conditions were met:  evaluation of the association of bariatric surgery and cancer risk;  inclusion of sufficient data or the data can be acquired to calculate ORs and 95% CIs;  the publication with the follow-up period at least 3 years;  all the studies were cohort studies; and  the study was published in English. Due to objective reasons, some valuable studies may be omitted because of insufficient data or data to calculate ORs and 95% CIs.
Given the multiple mechanisms by which obesity increases the risk of cancer [2, 3], we performed subgroup analysis; our results indicated that bariatric surgery was significantly associated with decreased breast cancer risk (OR = 0.49, 95% CI = 0.33–0.72) and endometrial cancer risk (OR = 0.43, 95% CI = 0.26–0.71). Reductions in cancer risk were strongest for postmenopausal breast and endometrial cancers. Both of these cancers are highly sensitive to estrogen levels [4, 5] and react rapidly to changes. Bariatric surgery results in rapid weight loss and has greater long-term success compared with non-surgical weight loss methods. Weight loss has been shown to reduce levels of circulating estrogen , thereby decreasing the risk of these cancers.
However, due to the limitations of our study, further studies estimating the functional effect and side effects may eventually provide a better, comprehensive understanding.
Zhang K, Luo Y, Dai H, Deng Z. Effects of bariatric surgery on cancer risk: evidence from meta-analysis. Obes Surg 2019 21
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Zhang, K., Luo, Y., Dai, H. et al. Response to “Letter to the Editor: Effects of Bariatric Surgery on Cancer Risk: Evidence from Meta-analysis”. OBES SURG (2020). https://doi.org/10.1007/s11695-020-04482-8