Clinical Characteristics and Prognosis of Coexisting Thyroid Cancer in Patients with Graves' Disease: A Retrospective Multicenter Study.

Background The association between Graves' disease (GD) and co-existing thyroid cancer is still controversial and most of the previously reported data have been based on surgically treated GD patients. This study investigated the clinicopathological findings and prognosis of concomitant thyroid cancer in GD patients in the era of widespread application of ultrasonography. Methods Data of GD patients who underwent thyroidectomy for thyroid cancer between 2010 and 2019 in three tertiary hospitals in South Korea (Asan Medical Center, Chonnam National University Hwasun Hospital, and Pusan National University Hospital) were collected and analyzed retrospectively. In the subgroup analysis, aggressiveness and clinical outcomes of thyroid cancer were compared nodular GD and non-nodular GD groups according to the presence or absence of the thyroid nodules other than thyroid cancer (index nodules). Results Of the 15,159 GD patients treated at the hospitals during the study period, 262 (1.7%) underwent thyroidectomy for coexisting thyroid cancer. Eleven patients (4.2%) were diagnosed with occult thyroid cancer and 182 patients (69.5%) had microcarcinomas. No differences in thyroid cancer aggressiveness, ultrasonographic findings, or prognosis were observed between the nodular GD and non-nodular GD groups except the cancer subtype. In the multivariate analysis, only lymph node (LN) metastasis was an independent prognostic factor for recurrent/persistent disease of thyroid cancer arising in GD (P=0.020). Conclusion The prevalence of concomitant thyroid cancer in GD patients was considerably lower than in previous reports. The clinical outcomes of thyroid cancer in GD patients were also excellent but, more cautious follow-up is necessary for patients with LN metastasis in the same way as for thyroid cancer in non-GD patients.