A new study published in JAMA Oncology has found that body mass index (BMI) and physical activity levels significantly influence the long-term risk of developing secondary cancers—also known as subsequent neoplasms—among survivors of childhood cancer.

Conducted by Dr. Lenat Joffe of Northwell Health in New Hyde Park, New York, and his colleagues, the large-scale retrospective cohort analysis included over 22,000 survivors who had been diagnosed with cancer before the age of 21 between 1970 and 1999. These individuals were tracked through September 2019, with researchers examining how BMI and exercise habits influenced later cancer risk.

The study revealed a clear pattern: survivors who were obese and physically inactive faced significantly higher risks of developing secondary cancers. Among the 22,716 participants, researchers identified 2,554 neoplasms in 2,156 individuals, with the median age at diagnosis for these subsequent cancers being 37.4 years.

Notably, individuals reporting no weekly physical activity had a 30-year cumulative incidence of secondary cancers at 18.6 percent—compared to just 10.9 percent among those who engaged in 15 to 21 metabolic equivalent hours per week (MET-h/wk) of exercise.

Obesity was linked to elevated risks of developing specific types of neoplasms: solid organ (22% higher risk), central nervous system (CNS) (47% higher risk), and skin cancers (30% higher risk). Conversely, higher levels of physical activity were associated with significant protective benefits—lowering the risk of these same cancers by 35% to 50%.

Further analysis showed specific links between obesity and reduced activity with the development of meningiomas and thyroid carcinomas. However, no significant association was found with breast or colorectal cancers or blood-related malignancies.

“The findings of this cohort study indicate that BMI and physical activity may considerably impact subsequent neoplasm risk long after completion of therapy,” the authors wrote, highlighting the long-term importance of lifestyle factors for cancer survivors.

While two authors disclosed financial connections to the biopharmaceutical and medical device sectors, the research offers important public health insights—emphasizing that maintaining a healthy weight and an active lifestyle could be key to preventing future cancers in a high-risk population.