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Obesity increases risk for secondary primary cancers in male survivors
Prediagnosis obesity may be a risk factor for overall and individual secondary primary cancers in male cancer survivors, according to a large cohort study.
“Although improvements in cancer screening and treatment have led to continuously increasing survival, these advances have been offset by an increased risk [for] secondary primary cancers,” Eun-Sook Lee, MD, PhD, division head of convergence technology and staff surgeon in the Center for Breast Cancer at Research Institute and Hospital of National Cancer Center in Korea, and colleague wrote. “Secondary primary cancers could be due to not only the late carcinogenic effects of cancer treatment but also the influence of shared behavioral risk factors or increased susceptibility to carcinogenesis.”
Despite its influence in risk for certain cancers, body weight has not been fully examined in association with secondary primary cancers.
Researchers had access to data from 11,204,372 men who had at least one Korean national health examination between 2003 and 2010. From this cohort, Lee and colleagues examined the associations between prediagnosis BMI and risk for secondary primary cancer in 239,615 male cancer survivors (mean age, 59.4 years) using data from the Korean National Health Insurance Service and National Cancer Registry.
Obese patients — defined a BMI of 25 or higher — accounted for 32.05% of cancer survivors and 33.93% of the entire cohort.
After 1.61 million person-years of follow-up, 4,799 patients reported with secondary primary cancers.
The age-standardized incidence rate of second cancers in survivors was 353.8 per 100,000 person-years, which was approximately 1.1 times higher than the incidence rate of first primary cancers (321.9 occurrences per 100,000 person-years; P < .001).
Analysis stratified by BMI demonstrated the age-standardized incidence rate was 23% higher for secondary primary cancers (391.9 occurrences per 100,000 person-years) than for the first primary cancer (318.3 occurrences per 100,000 person-years) among obese men.
Obese cancer survivors with a BMI of 25 to 30 demonstrated an elevated risk for all secondary primary cancers (adjusted HR [aHR] = 1.22; 95% CI, 1.13-1.32), as well as for secondary primary colorectal cancer (aHR = 1.35; 95% CI, 1.11-1.64), lymphoma (aHR = 1.89; 95% CI, 1.09-3.30), biliary tract cancer (aHR = 1.58; 95% CI, 1.04-2.39), kidney cancer (aHR = 2.23; 95% CI, 1.35-3.71), and obesity-related cancers (aHR = 1.28; 95% CI, 1.09-1.49) compared with patients with a BMI between 18.6 and 22.9.
Severely obese cancer survivors with a BMI of 30 or more also were more likely to develop any secondary primary cancer (aHR = 1.42; 95% CI, 1.15-1.74), as well as secondary primary liver (aHR = 2.34; 95% CI, 1.36-4.04) and kidney (aHR = 3.38; 95% CI, 1.27-9.01) cancers.
Researchers then compared BMI–associated risk for secondary primary cancer in survivors with risk for first primary cancer in the total cohort.
Among those with a BMI of at least 30, results showed the magnitude of the BMI–related secondary primary cancer risk in male cancer survivors (aHR = 1.41; 95% CI, 1.15-1.74) was stronger than that for first cancers in the general population (aHR = 1.12; 95% CI, 1.09-1.16).
The trends persisted, although to a lesser degree, among men with BMI between 25 and 30 (secondary cancer, aHR = 1.27; 95% CI, 1.12-1.43 vs. first cancer, aHR = 1.04; 95% CI, 1.03-1.06).
“These findings suggest that increased risk [for] 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,” Lee and colleagues wrote. – by Kristie L. Kahl
Disclosures: The researchers report no relevant financial disclosures.
Perspective
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Alok Khorana
Obesity is emerging as an important risk factor for both primary and recurrent cancers worldwide, with some even calling it the “new smoking” in reference to data linking tobacco abuse with malignancy.
The study by Park and colleagues focuses on male cancer survivors, a population known to be at risk for second malignancies. The researchers evaluated a cohort of nearly 240,000 Korean male cancer survivors, focusing especially on the risk for secondary primary cancers and its association with obesity.
Researchers report that prediagnosis obesity was, in fact, associated with risk for secondary primary cancers, with an HR of 1.41 for severely obese patients. These data confirm that obesity is a major risk factor for malignancy, and perhaps more so in patients who have already been diagnosed with one primary cancer.
It is important to note that obesity can be corrected with a variety of techniques including lifestyle modifications. These data suggest it is more urgent to adopt these behaviors or evaluate other techniques to reduce prevalence of severe obesity and hopefully risk for secondary malignancies.