Dr. Magdalena Plecka Ostlund at the Karolinska Institute in Stockholm and colleagues hypothesized that risk of obesity-related cancer decreases with time after obesity surgery. To investigate, they linked nationwide data on obesity surgery to new cases of breast, prostate, colorectal, endometrial, and kidney cancer recorded in the Swedish Cancer Registry, and calculated standardized incidence rates (SIR) among the obesity surgery patients compared to the general population.
“Among a total of 13,123 obesity surgery patients, contributing 125,049 person-years of follow-up, 296 new cases of obesity-related cancer were identified,” the researchers report in the Annals of Surgery, published online ahead of print on June 21.
Overall, there was no decrease in the SIR of obesity-related cancers with longer time after bariatric surgery, as the researchers had expected. “Yes, we were very surprised by the negative findings especially since the follow-up time is so long,” Dr. Plecka Ostlund said in response to an emailed query.
“However,” she continued, “the number of patients in each subgroup are small and maybe that’s why we can’t detect a positive effect of bariatric weight reduction on cancer risk in this study.”
One finding from the data analysis was that the risk of colorectal cancer increased with time after obesity surgery (p for trend 0.01). Dr. Plecka Ostlund offered this perspective: “It is difficult to draw definite conclusions from a single study. Our study is the only one of this kind, and that makes it difficult to say much about the increased risk of colorectal cancer, although the P for trend is significant.”
Asked if different results might possibly be seen in obese patients who have lost weight through non-surgical means, she said, “To my knowledge, there are no data on cancer risk after non-surgical weight loss, probably because this group of very obese individuals do not have a longlasting and substantial weight loss. It is also very difficult to follow this group over a long period of time; most cancers develop later in life, whereas obesity occurs early.”
The authors conclude in their report that efforts to prevent obesity rather than lose weight might be more worthwhile in terms of cancer prevention.
Risk of Obesity-Related Cancer After Obesity Surgery in a Population-Based Cohort Study
Ann Surg 2010.