Method of Detection of Well-Differentiated Thyroid Cancers in Obese and Non-Obese Patients.

Background: The incidence of well-differentiated thyroid cancer (WDTC) is increasing rapidly. Many authors feel that this increase is due to over-diagnosis and that one of the contributing factors is the increasing use of various imaging studies. The rate of obesity has also been increasing in the United States. It has been suggested that patients with an increased body mass index (BMI kg/m2) have a higher incidence of WDTC than patients with normal BMI. One might hypothesize that thyroid nodules are more difficult to palpate in obese patients and that as more cancers are detected by imaging the apparent rate of increase in WDTC in obese patients would appear to be greater than in non-obese patients. This study was undertaken to evaluate this hypothesis by determining if there is any difference in the way thyroid cancers are initially detected in obese and non-obese patients.

Methods: The medical records of all 519 patients with a postoperative diagnosis of WDTC who underwent thyroidectomy at NYU Langone Medical Center from January 1, 2007 through August 31, 2010 by the three members of NYU Endocrine Surgery Associates were reviewed. Patients were divided into Non-obese (BMI<30 kg/m2) and Obese (BMI≥30 kg/m2) groups. Patients were also divided by the initial method of detection of their tumor into Palpation, Imaging, and Incidental groups.

Results: The final study group contained 270 patients, 181(67%) of whom were in the Non-obese Group and 89(33%) were in the Obese Group. In the Non-obese group, 81(45%) of tumors were found by palpation, 72(40%) were found by imaging, and 28(16%) were found incidentally. In the Obese group, 40(45%) were found by palpation, 38(43%) were found by imaging, and 11(12%) were found incidentally. These differences were not statistically significant (p-value 0.769).

Conclusion: We show that BMI does not play a role in the method of initial detection in patients with WDTC. This suggests that the prevalence of WDTC detected by imaging is not an artifact caused by an increasingly obese population and that any association of WDTC and obesity is not related to the way in which these tumors are detected.