The relationship between body mass index and thyroid cancer pathology features and outcomes: a clinicopathological cohort study.

BACKGROUND: Obesity has been implicated as a predisposing and disease-modifying factor in cancer. Epidemiological studies suggest that obesity is associated with an increased risk of thyroid cancer; however, the relationships between obesity and thyroid cancer stage or behavior are uncertain. We hypothesized that a higher body mass index (BMI) would be associated with aggressive thyroid cancer features and a higher incidence of persistent/recurrent disease. METHODS: Two hundred fifty-nine consecutive patients with thyroid cancer were enrolled in this retrospective cohort study. Histopathological tumor features, stage at diagnosis, and disease status during and at the end of the study were determined based on chart review. BMI was calculated at the first clinical visit to our institution. The relationships between BMI and these parameters were assessed. RESULTS: Mean follow-up time for the group was 6.2 yr (0.11-46 yr). No positive associations were identified between BMI and T, N, or M stage at diagnosis, vascular invasion, or recurrent or persistent disease on univariate or multivariate analyses. The absence of an association was also demonstrated on analysis by BMI quartiles. An unexpected inverse association was identified between BMI and nodal metastasis and tumor invasion on both univariate and multivariate analyses, suggesting that obesity may be associated with less aggressive tumor features, a finding that requires confirmatory studies. CONCLUSION: Although obesity has been associated with increased thyroid cancer incidence, a higher BMI was found not to be associated with more aggressive tumor features or a greater likelihood of recurrence or persistence over the analyzed time period.