Advances in early detection, improved cancer treatments, and population growth in recent decades have led to exciting increases in cancer survivorship. However, with these increases comes increased risk of subsequent malignant neoplasms, which are the leading cause of morbidity and mortality among cancer survivors. This risk may be even greater for patients with overweight or obesity at the time of their first primary cancer diagnosis, as excess adiposity is an established cause of several common types of cancer. Dr Clara Bodelon and colleagues conducted a large cohort study (N=26,894) in the United States to explore the association between excess weight and risk of second cancers.
The study confirmed that a higher body mass index (BMI) is associated with increased risk of a second primary cancer among cancer survivors. Over a median follow-up of 7.9 years, 13.9% of patients were diagnosed with a second cancer, of which about one-third were obesity-related. The study found that high obesity was associated with a 34% increased risk of developing a second cancer and a 78% increased risk of developing an obesity-related cancer. The risk of a second cancer increased 13% for every 5-kg/m2 increase in BMI. The risk of developing an obesity-related cancer was even greater, increasing 28% for every 5-kg/m2 increase in BMI. Furthermore, compared with cancer survivors whose BMI was in the normal range, the risk of developing any second cancer was 15% higher for those who had overweight and 34% higher for those who had obesity.
In a linked editorial commentary, Dr Cari Kitahara suggested that these findings indicate a looming public health crisis, as the prevalence of obesity is rising and compounded by poor dietary quality and increased exposure to environmental pollutants, such as endocrine-disrupting chemicals, all of which are likely contributing to increased cancer rates among young people. Accumulation of endocrine-disrupting chemicals in adipose tissue is believed to further accelerate the carcinogenic effects of excess body weight. Additionally, with longer life expectancies, young cancer survivors are particularly susceptible to the adverse effects of overweight and obesity. Cumulative exposure to excess weight from a young age may have a greater impact on second cancer risk than excess weight gained in older age. Therefore, Dr Kitahara suggested that immediate public health action is needed at all levels to combat these concerning trends.
High level
These findings have important public health implications and may inform evidence-based survivorship guidelines. The association between excess weight and risk of second cancers in this study emphasizes the importance of recommending survivorship care guidelines for weight management and increasing awareness of second cancers among physicians of cancer survivors. Additionally, investments to address the social-level determinants and systemic barriers that contribute to the high prevalence of obesity are urgently needed.
Ground level
Physicians of cancer survivors should educate patients on the link between excess weight and risk of second cancers and consider appropriate screening for those who have overweight or obesity. Given that excess body weight is a modifiable risk factor, helping cancer survivors reach and maintain a healthy body weight may result in substantial health and quality-of-life benefits.