Background: Obesity is known as a risk factor of several cancers including breast, colon, esophagus, kidney, uterus, and thyroid. Recent studies have reported that higher body mass index (BMI) is also associated with more advanced stage. The aim of this study was to investigate the clinicopathological relevance between BMI and papillary thyroid carcinoma (PTC).
Methods: Four hundred seventy five patients surgically treated for PTC from July 2007 to December 2009 were included in this study. Medical records and pathologic reports were reviewed retrospectively. According to BMI, patients were divided into four groups : underweight (15, 3.2%), normal (273, 57.5%), overweight (151, 31.8%), and obese (36, 7.6%). Clinicopathological factors of each group were analyzed and compared between normal and other groups.
Results: Four hundred nineteen patients were women (88.2%) and fifty six patients were men (11.8%). Mean age was 48.4 years and mean follow-up period was 1436 ± 379.2 days. In comparison between the normal and underweight groups, there was significantly fewer cases of lymph node metastasis (0.095, 95% CI 0.011-0.780, p=0.028) but more cases with extra-thyroidal invasion (8.823, 95% CI 2.416-32.223, p=0.001) in the underweight group. There was no statistically significant difference between the normal and overweight groups. In the obese group, tumor size was significantly larger on univariate analysis (8.9 cm vs. 12.2 cm, p=0.007). However, there was no significant difference in lymph node metastasis, extra-thyroidal invasion, or recurrence between the normal and obese group.
Conclusion: Other than larger tumor size in the obese group, there was no other clinical significance between high BMI and PTC. Interestingly, fewer lymph node metastasis and more extra-thyroidal invasion were seen in the underweight group. A larger patient pool and further investigation will be needed to confirm these findings.