Association of Bariatric Surgery and Risk of Cancer in Patients With Morbid Obesity

Syed I. Khalid, MD; Samantha Maasarani, MD, MPH; Julia Wiegmann, MSCR; Aaron L. Wiegmann, MD, MS; Adan Z. Becerra, PhD; Philip Omotosho, MD; Alfonso Torquati, MD


Annals of Surgery. 2022;275(1):1-6. 

In This Article


A retrospective analysis of 28,908 exactly matched bariatric-eligible patients undergoing VSG, RYGB, or no surgical intervention was performed. Primary outcome analysis of our study revealed bariatric surgical intervention was associated with decreased rates of colorectal, liver, lung, ovarian, uterine, and any cancer within 5 years postoperatively compared to the no surgery cohort. Overall, previous literature has reached a similar conclusion on the benefits of bariatric surgery on cancer risk reductions.[32,33,36,41–44] However, there is conflicting evidence regarding its effects on colorectal cancer.[10,36–38] This may be due to the disruption of the normal gastrointestinal anatomy and vague postoperative abdominal systems, which may mask colorectal cancer lesions leading to delayed diagnosis.

Previous literature postulates that obesity prompts cancer by increasing levels and bioavailability of growth factors and sex steroid hormones, altering adipocytokines and the microbiomes, and inducing a chronic low-grade inflammatory state.[8,20,45–47] Chronic obesity leading to insulin resistance and consequently hyperinsulinemia promote higher levels of interaction between IGF-1 proteins and cell surface receptors, which stimulates tumor growth.[47] Furthermore, hyperinsulinemia causes upregulation of cellular metabolic activity leading to DNA damage and may potentially contribute to cancer development or progression.[47] Previous studies have concluded weight loss is more profound among those undergoing RYGB; however, both procedures have demonstrated significant and rapid weight loss.[27,29,38]

Several limitations should be considered when interpreting the results of this study. First, the accuracy and reliability of this data showed be considered as ICD-9 and ICD-10 codes depend on the subjective interpretation of physician records by a medical reviewer and are usually meant for financial and administrative purposes rather than research. Likewise, administrative data fail to note details such as surgeon technique/experience, cancer stage, and time of diagnosis, and specifically, ICD-9 and ICD-10 Diagnosis codes are undoubtedly underreported, but when reported, they are highly accurate.[48] As such, claims databases are not recommended for incidence or prevalence calculations but are more appropriate to develop cohorts for follow-up, which we have emulated. There also may be potential confounding factors in our study. Cancer rates in bariatric surgery patients may be higher due to the fact that these patients are receiving more routine imaging and follow-up visits as part of their postoperative course. Lastly, the observation of reduction of both obesity-related cancers as well as non–obesity-related cancers is peculiar given that there appears to be less biological plausibility for reductions in non–obesity-related cancers. This may reflect some of the limitations with the database as well as observational studies, which cannot out rule the possibility that the results are explained by selection bias and/or residual confounding. Nonetheless, the large reductions in obesity-related cancers suggest that these limitations would be difficult to explain the entire effect. If so, our results may be overestimating the impact of bariatric surgery. This limitation also applies when comparing patients who had undergone VSG versus RYGB, as the patient selection criteria for the two procedures can vary, and often RYGB is reserved for patients with the highest BMIs, and so may be a reason why VSG patients had lower cancer risk.

Despite these limitations, it is our hope that physicians may find our analysis interesting and clinically relevant. More importantly, we hope clinicians may be more inclined to consider bariatric surgical intervention as not only a treatment option for obesity but also as a preventative cancer measure.