Oct 06, 2014
By Shira Klapper, Senior Writer/Editor
Survivors of colorectal cancer (CRC) who are overweight or obese before their diagnosis have a significantly higher risk of being diagnosed with a second obesity-related cancer, compared to survivors of CRC who are of a normal weight before diagnosis. That’s according to the Journal of Clinical Oncology (JCO) study, “Body Mass Index and Risk of Second Obesity-Associated Cancers After Colorectal Cancer: A Pooled Analysis of Prospective Cohort Studies” which analyzed data from 11,598 survivors of colorectal cancer. Those survivors were part of five large cohort studies which followed 800,000 people over time to see who developed cancer. The study, published online, ahead of print, September 29, examined certain cancers related to obesity, including post-menopausal breast, kidney, pancreatic, esophageal adenocarcinoma, and endometrial.
Specifically, the study found that, compared to survivors of CRC who were of a normal weight before diagnosis, survivors of CRC who were overweight before diagnosis had a 39% greater risk of being diagnosed with a second obesity-related cancer, whereas those who were obese had a 47% greater risk.
The study also showed that the risks of obesity-related cancers among survivors of CRC were similar to risks of these cancers among individuals without a previous diagnosis of any cancer—suggesting that CRC survivors do not have unique susceptibility to developing cancers associated with obesity
|Todd M. Gibson, PhD
“We found no evidence that CRC survivors are different from individuals with no history of cancer in terms of the impact of obesity on cancer risk,” said Todd M. Gibson, PhD, a faculty member at St. Jude Children’s Research Hospital, who carried out the study while a post-doctoral fellow at the National Cancer Institute.
The results suggest that the increased risk for obesity-related cancers historically seen among survivors of colorectal cancer may be partially due to the fact that overweight and obesity—risk factors for second cancers—are more common in this group compared to the general population.
Patients should know: weight is important
The study reinforces existing guidelines regarding weight and CRC.
“Current guidelines advise CRC survivors to maintain a healthy body weight,” said Dr. Gibson. “And our results indicate that healthy body weight is just as important for risk of second cancers as for individuals without a history of cancer. These findings support the continued emphasis of this guideline.”
Dr. Gibson pointed out that the study only looked at how pre-diagnosis weight, and not changes in weight over time, affects someone’s risk of developing second cancers.
“Future work is needed to study even larger numbers of survivors and to measure weight over time to examine the long-term effects of changes in body weight on second cancer risk,” said Dr. Gibson.
Todd M. Gibson, PhD, is on the faculty in the Department of Epidemiology and Cancer Control at St. Jude Children’s Research Hospital, in Memphis. He has been an ASCO member since 2014.
(Click here to read the “American Society of Clinical Oncology Position Statement on Obesity and Cancer”).
Click here to read the abstract.
Click here to read the PDF.
Gibson TM, Park Y, Robien K, et al. Body mass index and risk of second obesity-associated cancers after colorectal cancer: a pooled analysis of prospective cohort studies. J Clin Oncol. Epub 2014 Sep 29.
The Exclusive Coverage series on ASCO.org highlights selected research from JCO and JOP with additional perspective provided by the lead or corresponding author.
@ 2014 American Society of Clinical Oncology