Bariatric surgery induced weight loss can help reduce the risk of cancer to rates almost similar to those of people of normal weight, according to the findings of the first comprehensive review published in Obesity Surgery. The review, which takes into into account relevant studies about obesity, cancer rates and bariatric surgery, concluded that the reasons for the findings were unknown but likely assocaited with weight loss or better awareness/diagnosis post surgery.
Some previous studies suggested a relationship between bariatric surgery and reduced cancer risk among obese people, as a result Dr Daniela Casagrande of the Universidade Federal do Rio Grande do Sul in Brazil. and her colleagues contrasted and combined results from 13 relevant studies that focus on the incidence of cancer in patients following bariatric surgery. These include both controlled and uncontrolled studies, and the relevant information of 54,257 participants.
They found that the cancer incidence density rate was 1.06 cases per 1,000 person-years within the surgery groups up to 23 years after the surgery was performed. This is markedly better than the rate for the global population of obese people. Importantly, the effect of bariatric surgery was found within both controlled and uncontrolled studies. Four controlled studies showed that bariatric surgery was associated with a reduction in the risk of cancer.
In the meta-regression, there was an inverse relationship between the pre-surgical BMI and cancer incidence after surgery (beta coefficient −0.2, p<0.05).
It is still unknown whether the lower cancer rates following bariatric surgery are related to the metabolic changes associated with weight loss, or if lower BMIs following surgery result in earlier diagnosis and improved cancer treatment outcomes among patients.
Casagrande said that it is difficult to separate the effects of the surgery from the multiple associated changes it yields in patients. She believes that undergoing a surgical procedure of the magnitude of bariatric surgery raises awareness and possible earlier diagnosis of cancer among such patients.
Although bariatric surgery is associated with reduced cancer risk in morbidly obese people, Casagrande notes that conclusions should be drawn with care because there was high heterogeneity among the studies.
In addition, there were some limitations about the data available among the studies and variables associated with cancer should still be measured in prospective bariatric surgery trials.