Therapy response and prognosis of different doses of 131I for low- and intermediate-risk differentiated thyroid carcinoma

Abstract:

Objective To investigate therapy response and progression-free survival（PFS） with different doses of ¹³¹I in postoperative patients with low- and intermediate-risk differentiated thyroid carcinoma（DTC）.Methods A total of 201 DTC patients with a total of 236 person-time ¹³¹I treatments with different doses of ¹³¹I were retrospectively analyzed. Serological and imaging indexes at 6 to 12 months after treatment were determined to evaluate the response of patients. And they were divided into four groups（G1 to G4 group） according to ¹³¹I administered activity（1.1 GBq once，1.1 GBq twice，3.0 GBq，3.7 GBq）. The patients were followed up for 12 to 90 months，and their serological， imaging and treatment records were collected after ¹³¹I therapy to assess the progression. Chi-square test and Fisher’s exact test were performed to compare the differences in efficacy response and influencing factors among the treatment groups. Kaplan-Meier method and log-rank test were used to compare the PFS. Cox proportional risk model was used to evaluate the independent risk factors for PFS.Results ①Total rate of excellent response（ER）/indeterminate response（IDR）/biochemical incomplete response（BIR）/structural incomplete response（SIR） among 4 groups were 41.5%（98/236），44.9%（106/236），6.8%（16/236） and 6.8%（16/236） respectively. ②The ER rates of G1 to G4 groups were 16.67%（10/60），42.86%（15/35），56.52%（13/23），and 50.85%（60/118）；the IDR rates of the four groups were 60.00% （36/60），45.71%（16/35），30.43%（7/23），and 39.83%（47/118）；the BIR rates of the four groups were 10.00%（6/60），0.00%（0/35），4.35%（1/23），and 7.63%（9/118）；the SIR rates of the four groups were 13.33%（8/60），11.43%（4/35），8.70%（2/23），and 1.69%（2/118） respectively. ③There was statistically significance in the rate of ER between G1 and G2/G3/G4（P=0.005；0.000；0.000） and SIR between G1 and G4（P=0.003）. ④The median follow-up time was 30 months，with progression observed in 18 patients（8.96%）. There were no significant differences in PFS among different doses of ¹³¹I（P=0.112）. Multivariate analysis showed that age and therapy response were independent prognostic factors for PFS.Conclusion The short-term ablation efficacy of ¹³¹I between multiple low-dose（1.1 GBq twice） group and high-dose（3.0 and 3.7 GBq） groups has no significant difference in postoperative patients with low- and intermediate-risk DTC. Different doses of ¹³¹I are not significantly related to PFS. For patients with ER and aged < 55 years，there is a PFS benefit.