Obesity Associated With Increased Risk of Advanced Thyroid Cancer

A new study shows that obese patients are more likely to have advanced papillary thyroid cancer and for the cancer to be of an aggressive subtype.

Researchers at the David Geffen School of Medicine at UCLA sought to determine whether a higher body mass index (BMI) was associated with a more aggressive and advanced form of papillary thyroid cancer and worse surgical outcomes. Previous population studies have shown a trend of increased incidence of thyroid cancer in patients with higher BMI.

Lymph node with papillary thyroid cancer; source: Nephron, Wikimedia Commons

The study, published in the Archives of Surgery, shows that patients who are obese are more likely than regular-weight patients to have advanced papillary thyroid cancer, and for the cancer to be of an aggressive subtype.

Why obesity appears to be linked to more advanced forms of thyroid cancer is not yet clear according to lead study author, Avital Harari, MD, section of endocrine surgery, University of California, Los Angeles.

The retrospective review analyzed results of 443 patients who underwent total thyroidectomy due to a papillary thyroid cancer diagnosis as a first-line treatment. Patients were between 18 and 93 years old. The median age was 48.2 years. Patients were categorized into four BMI categories: normal, overweight, obese, and morbidly obese. Greater BMI was associated with more advanced disease at presentation (P < .001) and a more aggressive histopathologic subtype (P < .03). Morbidly obese patients were more likely to present with stage III or IV disease (P < .001).

A greater BMI was also associated with a longer duration of anesthetic induction and longer hospital stay, but not a longer time in surgery or more complications. The study, however, was underpowered to detect a low complication rate, said Dr. Harari.

Thyroid cancer cases are increasing in the United States, mostly due to an increase in the number of papillary thyroid cancer cases. It is not clear, however, whether this is due to increased detection or to a higher risk of development of the cancer. Obesity is a risk factor for many cancer types and BMI has been found to be associated with colon cancer, endometrial cancer, renal cancer, and esophageal carcinoma, according to the study authors. As more people in the United States are becoming obese, there is a clear health concern that includes a high risk of cancer.

The current study results are likely to be multifactorial, according the researchers. Factors that influence the association between obesity and thyroid cancer include a delayed diagnosis in higher BMI patients due to the difficulty of detecting thyroid nodules in the neck, and biomarkers such as higher leptin levels known to be associated with cancer development and progression. Another link between thyroid cancer and obesity may be mediated by diabetes. A National Institute of Health–AARP diet and health study of 500,000 patients showed an increased risk of papillary thyroid cancer in women with diabetes, the authors cite. Dr. Harari and colleagues recommend more vigilant screening of thyroid cancer for obese patients.


1. Harari A, Endo B, Nishimoto S, et al. Risk of Advanced Papillary Thyroid Cancer in Obese Patients. Arch Surg. 2012 May. [Epub ahead of print]