The incidence of papillary thyroid carcinoma and outcomes in operative patients according to their body mass indices

Background. The connection between high body mass index (BMI), risk of papillary thyroid carcinoma (PTC), and the aggressiveness of PTC is still debated. We aimed to establish the relationship between excess BMI and the risk of PTC in an operative population, and the impact of obesity on histopathologic aggressiveness of PTC and on the outcome of patients. Methods. All consecutive patients who underwent thyroid operation from June 2002 to December 2009 were reviewed in this retrospective study. BMI groupings were based on standardized categories: normal-weight, overweight, and obesity. We performed a total thyroidectomy with lymph node dissection in patients with preoperative or operative diagnosis of PTC. Radioiodine ablation was performed in every N1 patient, in case of tumor size greater than 10 mm, and if there was extrathyroidal invasion. During a median follow-up of 6.2 years, patients who were retreated by operation or I-131 were considered to have a persistent (<18 months of the initial operative treatment) or recurrent (>= 18 months) disease. Results. Of 6,684 patients who had a thyroid gland resection, we identified 1,216 (18.2%) patients with PTC. Patients who were overweight or obese were not at greater risk of PTC than normal-weight subjects. Indications for operation or radioiodine therapy were similar in the three BMI groups. During follow-up, 86 patients (7.1%) experienced persistent (4.5%) or recurrent (2.5%) disease. When excluding micro-PTCs (<= 10 mm), we found an association between recurrent or residual locoregional thyroid cancer and BMI: 18.7% in obese patients versus 8.5% if BMI <25 kg/m(2) and 9.8% if 25 >= BMI < 30 kg/m(2) = .03). This difference was clearly marked for persistence. When adjusted for other cofounder factors, we observed that BMI was an independent factor associated with the risk of postoperative locoregional event (odds ratio 3.8, 95% confidence interval 1.6-8.8), with sex, age, lymph node metastasis, and tumor bilaterality. Conclusion. In macro-PTC, obese patients had an increased risk of developing a locoregional event during the follow-up, specifically a persistence of the disease. According to these results, overweight and obese patients with macro-PTC should be monitored more carefully for early detection of cancer persistence.