ObjectiveTo investigate the predictive value of differential distribution of peripheral lymphocyte subsets before and after the first ¹³¹I treatment on the therapeutic response to ¹³¹I treatment in patients with papillary thyroid cancer (PTC).

MethodsA retrospective study was conducted on 46 PTC patients (16 males, 30 females, age 20-77 years) who underwent total thyroidectomy and received ¹³¹I treatment between January 2021 and August 2021 in First Hospital of Shanxi Medical University. Peripheral blood lymphocyte subsets (T, B, CD4 ⁺ T, CD8 ⁺ T, natural killer (NK), helper T (Th)1, Th2, Th17, and regulatory T (Treg) cells) were measured 1-2 d before and 30 d after ¹³¹I treatment. Based on serological and imaging evidence, therapeutic response at 6-12 months post- ¹³¹I therapy was categorized as either excellent response (ER) or non-excellent response (NER). Differences of preablative stimulated thyroglobulin (psTg) and clinical baseline characteristics between two groups were assessed by using independent-sample t test, paired t test, or Mann-Whitney U test. Predictive value of lymphocyte subsets before and after ¹³¹I treatment for therapeutic response was assessed through logistic regression analysis, ROC curve analysis, and decision curve analysis (DCA).

ResultsIn ER group ( n=33) and NER group ( n=13), most lymphocyte subsets showed different degrees of reduction 30 d after ¹³¹I treatment compared to before ¹³¹I treatment, such as T, B, CD4 ⁺ T and Th1 cells in ER group, as well as T, B, CD4 ⁺ T, Th1, Th2, Th17, and Treg cells in NER group ( t values: 2.41-9.57, all P<0.05). Before ¹³¹I treatment, NER group had significantly higher levels of psTg, Th2, Th17, and Treg cells compared to the ER group ( t values: from -3.32 to -2.48, U=29.00, all P<0.05). After ¹³¹I treatment, most of lymphocyte subsets in NER group (T, B, CD4 ⁺ T, CD8 ⁺ T, Th1 and Treg cells) showed higher trend than those in ER group but without statistical significances ( t values: from -1.12 to -0.06, all P>0.05). Th2 cells before ¹³¹I treatment (odds ratio ( OR)=25.00, 95% CI: 1.36-459.10, P=0.030) was identified as a risk factor for NER. ROC curve analysis indicated that AUCs of psTg and Th2 cells for predicting therapeutic response were 0.932 and 0.790, respectively, which was 0.958 for the combined psTg and Th2 cells. DCA showed that within the threshold probability range of 10%-60%, the curves for psTg, Th2 cells, and the combined psTg and Th2 cells were all higher than the extreme curve, suggesting good effect.

ConclusionsMost lymphocyte subsets decrease to varying degrees, and NER group shows a significant decrease 30 d after ¹³¹I treatment. Th2 cells may be a risk factor for poor response to ¹³¹I treatment, providing a certain value in predicting the therapeutic response to ¹³¹I treatment.