Male cancer survivors who were obese before their cancer diagnosis may be at a higher risk of developing a second primary cancer later, such as lymphoma, according to the results of a large prospective study conducted in South Korea.
The study, “Prediagnosis Body Mass Index and Risk of Secondary Primary Cancer in Male Cancer Survivors: A Large Cohort Study,” published in the Journal of Clinical Oncology, adds to extensive data that supports the belief that obesity could increase the risk of secondary cancer.
Dr. Sang Min Park, MD, PhD, and colleagues from the Seoul National University College of Medicine in South Korea merged data from the Korean National Health Insurance Service (NHIS) and National Cancer Registry on more than 11 million men.
Following eight years of follow-up, among the approximately 230,000 men who were diagnosed with a first cancer, 4,799 of them later developed secondary primary cancers (SPCs). Body mass index (BMI) before the diagnosis of the first cancer was positively associated with the risk of colorectal, liver, lymphoma, kidney, biliary tract, and obesity-related SPCs.
Because cancer influences body weight, they examined the association between obesity before the first cancer diagnosis and diagnosis of the second primary cancer. The association between BMI and the risk for second primary cancers was stronger in male cancer survivors compared to men in the general population for development of first cancers.
After adjusting the data for confounding factors, the researchers found that male cancer survivors with a BMI of 30 or higher before being diagnosed with their first cancer had a 41 percent higher chance of developing a secondary primary cancer than cancer survivors with a normal BMI.
But in general, men with a BMI of 30 or higher had only a 12 percent increased chance of developing a first primary cancer.
“These findings suggest that increased risk of cancer among cancer survivors might be partially due to an increased prevalence of obesity or an increased susceptibility to obesity-related carcinogenesis among cancer survivors compared with the general population,” the researchers wrote in their study.