Endocrine Abstracts

JOINT1673

Objective: To analyze the progression of plasma thyroglobulin (Tg) levels and dynamic risk stratification (DRS) in patients diagnosed with differentiated thyroid cancer (DTC) without radioactive iodine treatment in a thyroid unit.

Materials and Methods: A prospective study was conducted on all patients who underwent thyroidectomy or hemithyroidectomy with a diagnosis of DTC and did not receive radioactive iodine treatment between 2020 and 2024. Clinical, biochemical, and imaging data were collected at diagnosis and during follow-up.

Results: A total of 66 patients without radioactive iodine treatment were evaluated (80.3% women, mean age 55.6±11.7 years, 72.7% were diagnosed incidentally and an average DTC follow-up of 2.0±1.3 years). The most common DTC subtype was classic papillary carcinoma in 42.4% of cases. Total thyroidectomy was performed in 75.8% of patients, while 24.2% underwent hemithyroidectomy. The mean tumor size was 8.0±7.2 mm (30.3% of cases >1 cm). Histopathological characteristics included multifocality in 31.8% of cases, bilaterality in 21.2%, and capsular invasion in 18.2%. The tumor stage was I, with all patients classified as having a low risk of recurrence. When evaluating DRS (Momesso et al.) in the total cohort three months after surgery, 39.3% of patients had an indeterminate response (IR), 57.1% had an excellent response (ER), and 3.6% had a biochemical incomplete response. At the end of the mean follow-up, 60.5% had an ER, while 39.5% had an IR (P <0.05). However, there were no significant differences in Tg levels during follow-up, either in the overall sample (1.5±2.3 vs. 1.3±1.2, not significant) or by type of surgery. Among those patients who underwent total thyroidectomy, 88% had Tg <1 ng/ml, whereas 100% of those who underwent hemithyroidectomy had Tg <30 ng/ml. When correlating baseline circulating Tg levels with those from the last follow-up visit, a strong positive correlation was observed (r = 0.916, P <0.001). However, no correlation was found with TSH levels. Finally, when analyzing initial DRS in total thyroidectomy patients in relation to different clinical and histopathological characteristics, no significant differences were found in age, sex, or histological features predicting disease progression, except for a larger tumor size in the IR group (8.7±4.9 vs. 6.4±3.2 mm, P <0.05).

Conclusions: A total of 60.5% of patients exhibited an ER from diagnosis, maintaining stability during follow-up despite not receiving radioactive iodine treatment. DRS was associated only with tumor size and not with other clinical or histological features. Baseline circulating Tg levels correlated with final Tg levels.