Long-term outcome of rare oncocytic papillary (Hürthle cell) thyroid carcinoma following (adjuvant) initial radioiodine therapy

Purpose Oncocytic (Hürthle cell) papillary thyroid carcinoma (OPTC) is a rare variant of the papillary thyroid carcinoma (PTC) which comprises approximately 1 to 11 % of PTC cases. Its clinical course and prognosis have not been comprehensively documented and the clinical outcome remains a controversial issue. Therefore, we investigated the long-term prognosis after thyroidectomy and (adjuvant) initial radioactive iodine therapy (RIT) of OPTC compared to PTC. Methods A total of 563 patients (47 with OPTC and 516 with PTC) with a median follow-up of 9.9 (0.3; 23.5) years were studied. All patients underwent thyroidectomy followed by (adjuvant) initial RIT. Data on the patients’ demographics, pathology, laboratory findings, imaging studies, treatment, and follow-up including recurrence, and disease-specific survival were collected. Cox’s multivariate regression model was used to identify independent prognostic factors for survival. Results OPTC patients were significantly older (55.2 ± 12.3 years) than PTC patients (50.3 ± 13.5) at the time of initial diagnosis ( p value 0.016). Initial tumor size was larger in the OPTC group (2.8 ± 1.8 cm for OPTC patients, 1.5 ± 1.2 cm for PTC patients, p value < 0.001). Before matching, OPTC patients presented more often with evidence of disease at the last visit of follow-up ( p value 0.046). However, this difference was not observed anymore after matching for risk factors ( p value 0.637). Disease-specific survival did not differ significantly. Age (HR, 1.183; 95% CI, 1.097–1.276) was identified as an independent prognostic factor for disease-specific survival. OPTC patients predominantly showed a recurrence of distant metastasis within a shorter time despite being not statistically significant. Conclusion At initial diagnosis, OPTC shows significant differences in terms of age and initial tumor size compared to PTC. Patients suffering from OPTC present with the same clinical long-term outcome indifferent to PTC after (adjuvant) initial RIT after matching.