Obesity Linked to Higher Risk for Aggressive Thyroid Cancer

Roxanne Nelson

May 22, 2012

May 22, 2012 — Patients who are obese tend to present with more aggressive forms of papillary thyroid cancer. In addition, the cancer is often diagnosed at a more advanced stage in this population, according to a retrospective review.

The study, published online May 21 in the Archives of Surgery, found that obese and morbidly obese patients presented more frequently with stage III or IV disease (P = .04).

A subgroup analysis showed that the percentage of the more aggressive tall cell variant of papillary thyroid cancer was significantly higher in obese and morbidly obese patients than in those who were of normal weight or merely overweight (P = .03). A higher body mass index (BMI) was associated with a longer duration of anesthesia induction (P < .001) and a longer stay in the hospital (P < .001).

The findings from this study are very interesting, explained lead author Avital Harari, MD, assistant professor of surgery at the University of California, Los Angeles, David Geffen School of Medicine.

"I believe the reason for the increase in late-stage and more aggressive thyroid cancer in obese individuals is 2-fold," she told Medscape Medical News. "One reason is that obese patients typically have a delay in diagnosis in relation to most illnesses. In the case of thyroid cancer, it's likely that their cancers and nodules are not felt on physical exam because of larger neck sizes."

It is also likely that the state of obesity itself, physiologically, contributes to an increase in aggressive cancers, Dr. Harari added.

Take-Home Message

Primary care physicians, endocrinologists, and thyroid surgeons "should be vigilant about assessing their obese patients for thyroid cancers. It is important to be aware of the increased risk for these individuals not only for thyroid cancers, but for all other types as well," Dr. Harari noted.

For thyroid cancer, there is currently no recommendation for screening, she pointed out. "Our data suggest that there should be thyroid cancer screening for those at higher risk, such as obese patients. Our recommendation mirrors a similar proposal for breast cancer screening, where studies have suggested that a more vigilant mammogram screening regimen should be instituted for obese patients."

On the basis of their data, Dr. Harari and colleagues suggest that obese patients older than 45 years be screened sonographically for thyroid cancer. The reasoning for this is that although most thyroid cancers are treatable, people who present in the late stages have a true increase in mortality. "If their cancers can be caught earlier, the assumption is that mortality can be decreased," she explained. "One of our next studies will be to perform a cost-effectiveness analysis to determine the feasibility of this screening recommendation and its cost/benefit ratio."

Study Details

Dr. Harari and colleagues conducted a retrospective review of a prospective database of patients who underwent total thyroidectomy as an initial procedure for papillary thyroid cancer or its variants, from January 2004 to March 2011, at a single tertiary referral center. The goal of their study was to determine whether a higher BMI is associated with more aggressive disease and adverse surgical outcomes.

The mean age of the cohort used in the final analysis (n = 443) was 48.2 years (range, 18 to 93 years). Patients were categorized by BMI: normal (18.5 to 24.9 kg/m²), overweight (25.0 to 29.9 kg/m²), obese (30.0 to 39.9 kg/m²), and morbidly obese (above 40.0 kg/m²).

Patients of normal weight tended to be slightly younger than patients in the other BMI categories (P < .001). There were more women than men in the cohort, but there were more overweight and obese men (P < .001). In addition, black patients were more likely to be obese and morbidly obese than people other races (P < .001).

Overall, a higher BMI was associated with more advanced disease stage at presentation (P = .04), but the researchers found no difference in the histologic subtype of papillary cancer among the BMI groups.

There was no association between the tall cell variant and age (P = .62), but there was a trend toward larger tumor size in patients with a higher BMI.

The researchers did not find any association between total surgical complication rates and BMI, although patients in the obese group had significantly more recurrent laryngeal nerve dysfunction (n = 10; 12.2%) than those in the normal weight (n = 2; 2.0%) and overweight (n = 3; 2.6%) groups. The bulk of this was related to presentation with preoperative vocal cord dysfunction with more advanced local disease, they write.

In addition, obese patients (n = 9) had more preoperative vocal cord paralysis related to local invasion (odds ratio [OR], 9.2; 95% confidence interval [CI], 1.9 to 43.9; P = .001) than patients of normal weight (n = 2).

Good News and Bad News

During the past few decades, the incidence of thyroid cancer has increased in the United States, but the reasons for the rising rates are not completely clear, writes Quan-Yang Duh, MD, in an accompanying editorial. Some of the reasons for this increased risk might be earlier diagnosis and some "as-yet unidentified environmental risks (radiation perhaps?)."

"This parallel increase in the rates of obesity and thyroid cancer is intriguing, but without a much larger population study, we cannot determine whether obesity causes thyroid cancer," says Dr. Duh, who is professor of surgery at the University of California, San Francisco.

"For obese patients with papillary thyroid cancer, the bad news is that the cancer is likely to be more advanced," he notes. "The good news is that thyroid operation remains safe even in obese patients with advanced disease."

He notes that although obese patients pose technical and clinical challenges for surgeons, such as longer anesthesia and operating times, there was a "somewhat surprising" lack of increase in surgical complications.

"The higher rate of recurrent laryngeal nerve palsy in obese patients is explained by the invasion of recurrent laryngeal nerve by advanced cancer before the operation," he says, but there were no increased rates for complications such as deep venous thrombosis, pneumonia, respiratory distress, and urinary tract infection, "as one would have expected."

The study authors and Dr. Duh have disclosed no relevant financial relationships.

Arch Surg. Published online May 21, 2012. Abstract, Editorial

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