Clinical significance of maximum diameter of lymph node metastasis in patients with differentiated thyroid cancer and its effect on 131 iodine therapy

Introduction: Objective (1) the relationship between the maximum diameter of lymph node metastasis and the therapeutic effect of 131 iodine in patients with differentiated thyroid cancer. (2) Relationship between maximum diameter of lymph node metastasis and tumor invasiveness in patients with differentiated thyroid cancer.

Background: due to its own tumor inertia, most patients with differentiated thyroid cancer (DTC) can achieve a good clinical prognosis after standardized surgery, radioactive iodine therapy and hormone inhibition therapy, but the probability of lymph node metastasis and recurrence is still high, about 50% and 20% respectively. In this study, we will explore the clinical significance of the maximum diameter of lymph node lesions and its pathological features and its impact on 131 iodine therapy.

Methods: The patients with differentiated thyroid cancer (DTC) who underwent 131I treatment for the first time in our department from June 2014 to June 2017 were analyzed retrospectively. Inclusion criteria: 1) patients who received 131 iodine treatment in our department for the first time during 14-17 years (2) total or near total thyroidectomy and neck lymph node dissection (PN1 confirmed by pathology) (3) follow-up time ≥ 1 year. Exclusion criteria: lack of necessary lymph node pathological information. According to the maximum diameter of cervical lymph node metastasis, the patients were divided into three groups (group 1: the maximum diameter of lymph node metastasis was less than 0.2cm; group 2: the maximum diameter of lymph node metastasis was 0.2-1cm; group 3: the maximum diameter of lymph node metastasis was more than 1cm). The therapeutic effect of 131I was evaluated by 2015 ATA guidelines. SPSS 26.0 statistical software was used for analysis, and all measurement data were expressed by mean ± standard deviation (± s) or median. ROC proportional hazards regression analysis was used to determine the critical value of the effect of the maximum size of lymph node metastasis on the efficacy of 131 iodine; Univariate and multivariate logistic regression analysis was used to determine the effect of lymph node pathological characteristics on the efficacy of 131 iodine therapy

Results: At present, 255 postoperative patients with thyroid cancer without structural lesions in 2016 are included in this study, excluding 135 patients who lack necessary lymph node medical record information, 36 patients who were lost to follow-up, 42 patients with distant metastasis found in the first diagnosis, 4 patients with out of hospital treatment or incomplete data, and 150 patients with structural lesions. Group 1: 56 patients whose maximum diameter of lymph node metastasis was less than 0.2cm; Group 2: 147 patients with lymph node metastasis with the maximum diameter of 0.2-1cm; Group 3: 52 patients with the maximum diameter of lymph node metastasis greater than 1cm. There were significant differences in gender, age, BMI, BRAF positive primary tumor, number of positive lymph nodes, T stage, N stage, lymph node invasion and lymph node fusion among the groups. According to the evaluation of the efficacy of iodine treatment in 2015 ATA guidelines, there was a statistically significant difference between the three groups (P = 0.015). In the further exploration of the evaluation of the effect of the maximum diameter of lymph node lesions, the ROC curve showed that the maximum metastatic diameter of lymph node lesions was 0.425cm as the critical value, AUC = 0.634 (95% CI 0.554-0.715; P = 0.001).

Conclusions: The risk factors affecting the maximum diameter of lymph node lesions include the number of metastatic lymph nodes, lymph node invasion, lymph node fusion, BRAF gene and TNM stage. When the maximum diameter of lymph node lesions is small, 131 iodine has a good therapeutic effect.