A new study entitled “Body Mass Index and Risk of Second Obesity-Associated Cancers After Colorectal Cancer: A Pooled Analysis of Prospective Cohort Studies” published in the September issue of Journal of Clinical Oncology, reports previous overweight or obesity diagnosis in colorectal cancer survivors increases the risk of second obesity-associated cancers.
In the United States alone, 1.1 million people are currently diagnosed with colorectal cancer (CRC). Being overweight and obesity are risk factors associated with different types of cancer, including breast, pancreas and kidney. However, a clear association has been established between primary CRC and excess body fat. Furthermore, in CRC survivors, there is an increased tendency to suffer from a second type of cancer. This association suggests that obesity could be contributing to an increased susceptibility in CRC patients to develop obesity- associated cancers.
In this study, the authors aimed to determine if CRC survivors with a pre-diagnosis of obesity were more prone to develop a second obesity-related cancer, and if so, would CRC survivors have an increased susceptibility to these types of cancer when compared with cancer-free subjects.
The authors analysed five prospective cohort studies, analyzing a total of 12,000 CRC survivors with an average age of 69 years upon diagnosis, and found that overweight or obese individuals prior to diagnosis had a higher risk of a second obesity-associated cancer.
Dr. Todd Gibson, the study first author explained in a HealthDay interview “We found that colorectal cancer survivors who reported being overweight or obese prior to diagnosis had a modestly increased risk of developing an obesity-related second cancer compared to [cancer survivors] who reported a normal weight.”
However, the authors noted that obese or overweight CRC survivors had no increased risk of developing obesity-related cancers when compared to overweight general population without colorectal cancer. This allowed the team to conclude that it is not the history of obesity but rather the excess weight per se that increases the risk of developing a second malignancy.
Dr. Gibson concluded, “The implication is that maintaining a healthy weight is important for cancer prevention in colorectal cancer survivors, just as it is in the general population. Our results further emphasize the importance of existing guidelines recommending healthy weight for survivors.”