Excess Body Weight Tied to Increased Risk for Second Cancers

TOPLINE:

Cancer survivors who had overweight or obesity at the time of their initial cancer diagnosis have a higher risk for a second primary cancer, particularly an obesity-related cancer, a new analysis found.

METHODOLOGY:

• Cancer survivors have an increased risk for another primary cancer. Studies suggest that lifestyle factors, such as excess body weight, may contribute to the risk for a second cancer; however, prospective long-term data on this association remain limited.
• Researchers evaluated 26,894 participants (mean age at first cancer diagnosis, 72.2 years; 97.6% White) from the Cancer Prevention Study II Nutrition cohort, who were diagnosed with a first nonmetastatic primary cancer between 1992 and 2015.
• Body mass index (BMI) was calculated from self-reported data at the time of the first primary cancer diagnosis; 10,713 participants had a normal BMI (18.5 to
• The study outcomes were the incidences of any second primary cancer and obesity-related second cancers.
• The most common first primary cancers were prostate (35.0%), breast (19.1%), and colorectal (9.5%) cancers; almost 40% of all first primary cancers were related to obesity.

TAKEAWAY:

• Overall, 13.9% participants (3749 of 26,894) were diagnosed with a second cancer over a median of 7.9 years; 33.2% of these cancers were related to obesity.
• Compared with participants with a normal BMI, those who had overweight had a 15% higher risk for any second cancer (adjusted hazard ratio [aHR], 1.15) and a 40% higher risk for an obesity-related second cancer (aHR, 1.40). Additionally, those with obesity had a 34% higher risk for any second cancer and a 78% higher risk for an obesity-related second cancer.
• For every 5-unit increase in BMI, the risk for an obesity-related cancer (aHR, 1.28) was considerably higher than the risk for any second cancer (aHR, 1.13).
• Among all survivors, every 5-unit increase in BMI was associated with a 42% increased risk for colorectal cancer as a second cancer (aHR, 1.42) and a 70% higher risk for kidney cancer as a second cancer (aHR, 1.70).

IN PRACTICE:

“In this cohort study of older survivors of nonmetastatic cancer, those who had overweight or obesity at the time of their first cancer diagnosis were at higher risk of developing a second cancer, especially obesity-related cancers,” the authors wrote. “These findings have important public health implications and may inform evidence-based survivorship guidelines to reduce the risk of second primary cancers among cancer survivors.”

SOURCE:

This study, led by Clara Bodelon, PhD, MS, American Cancer Society, Atlanta, was published online in JAMA Network Open.

LIMITATIONS:

The exclusion of multiple primary cancers in the same site could have underestimated the magnitude of the association of excess body weight with the risk for second primary cancers. BMI was used as a measure of excess body fat in this study, which does not differentiate between fat and lean mass. Unmeasured or residual confounding factors might be present.

DISCLOSURES:

The study was supported by grants from the Centers for Disease Control and Prevention’s National Program of Cancer Registries and cancer registries supported by the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program. No relevant conflicts of interest were disclosed by the authors.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.