Post-operative stimulated thyroglobulin and neck ultrasound as personalized criteria for risk stratification and radioactive iodine selection in low- and intermediate-risk papillary thyroid cancer

Abstract

The purpose of this study was to demonstrate the utility of a personalized risk stratification and radioactive iodine (RAI) selection protocol (PRSP) using post-operative stimulated thyroglobulin (Stim-Tg) and neck ultrasound in low- and intermediate-risk papillary thyroid carcinoma (PTC) patients. Patients with PTC tumors ≥1 cm were prospectively followed after total thyroidectomy and selective therapeutic central compartment neck dissection. Low/intermediate risk was defined as PTC confined to the thyroid or central (level VI) lymph nodes. Stim-Tg and neck ultrasound were performed approximately 3 months after surgery and used to guide RAI selection. Patients with Stim-Tg < 1 µg/L did not receive RAI, while those with Stim-Tg >5 µg/L routinely did. Those with Stim-Tg 1-5 µg/L received RAI on the basis of several clinical risk factors. Patients were followed for >6 years with serial neck ultrasound and basal/stimulated thyroglobulin. Among the 129 patients, 84 (65 %) had undetectable Stim-Tg after initial surgery, 40 (31 %) had Stim-Tg of 1-5 µg/L, and 5 (4 %) had Stim-Tg >5 µg/L. RAI was administered to 8 (20 %) patients with Stim-Tg 1-5 µg/L and 5 (100 %) with Stim-Tg >5 µg/L. Using this approach, RAI therapy was avoided in 17/20 (85 %) patients with tumors >4 cm, in 72/81 (89 %) patients older than 45 years, and in 6/9 (67 %) patients with central lymph node involvement. To date, 116 (90 %) patients in this cohort have not received RAI therapy with no evidence of residual/recurrent disease, whereas among the 13 patients who received RAI, 1 (8 %) had pathologic residual/recurrence disease. Using the proposed PRSP, RAI can be avoided in the majority of low/intermediate-risk PTC patients. Moreover, traditional risk factors considered to favor RAI treatment were not always concordant with the PRSP and may lead to overtreatment.