Decision-making value of a 1-cm tumor diameter cut-off for postoperative ¹³¹I treatment in papillary thyroid...

To evaluate the decision-making value of a 1-cm tumor diameter cut-off for radioactive iodine (¹³¹I) therapy in papillary thyroid microcarcinoma (PTMC).

This retrospective study included 291 patients who received post-operative ¹³¹I treatment: 123 with PTMC (≤1 cm, n=123) and 168 with papillary thyroid non-microcarcinoma (PTNMC, >1 cm, n=168). Clinicopathologic characteristics, initial treatment goals (remnant ablation, adjuvant therapy, eliminate residual lesions), administered dose (100/150 mCi), and serologic indices [pre-therapy thyroid-stimulating hormone (TSH) and stimulated thyroglobulin (sTg), as well as 6-month sTg] were compared. Therapeutic response was assessed at the last follow-up based on recurrence risk stratification and initial treatment goals.

Compared to the PTNMC group, the PTMC group showed lower rates of capsular invasion (40.65% vs. 59.52%), extraadenal invasion (12.20% vs. 23.21%), >5 lymph node metastases (38.21% vs. 57.74%), T3b/T4 stage (5.69% vs. 16.07%), pre-therapy sTg ≥10 μg/L (17.89% vs. 37.50%), and high recurrence risk (13.01% vs. 24.40%) (all P<0.05). PTMC patients more frequently underwent remnant ablation (64.23% vs. 44.64%) and received 100 mCi (78.86% vs. 57.14%), while PTNMC patients more often received adjuvant therapy (50.00% vs. 32.52%) and 150 mCi (42.86% vs. 21.14%) (all P<0.05). Pre-therapy sTg (6.78 ± 3.11 vs. 11.23 ± 5.91 μg/L) and 6-month sTg (1.52 ± 0.75 vs. 2.89 ± 1.37 μg/L) were lower in the PTMC group (P<0.001).

A 1-cm diameter cut-off had limited standalone value in guiding ¹³¹I treatment decisions for PTC.