Residual radioactivity and its influencing factors in patients with differentiated thyroid carcinoma after 131I therapy / 中华核医学与分子影像杂志

ABSTRACT

Objective:To analyze the trends and influencing factors of residual radioactivity in patients with differentiated thyroid carcinoma (DTC) after 131I therapy. Methods:A total of 132 DTC patients (34 males, 98 females; age (42.8±12.8) years) who received 131I therapy from November 2018 to February 2019 in Tianjin Medical University General Hospital were prospectively analyzed. Patients were divided into first treatment (FT) group ( n=88) and repeat treatment (RT; with 131I treatment≥2 times) group ( n=44). In FT group, there were 30 patients received 131I for remnant ablation, 33 patients for adjuvant therapy and 25 patients for therapy. In RT group, there were 18 patients received 131I for remnant ablation and 26 patients for therapy. 131I dosage: 3.70 GBq for remnant ablation therapy, 3.70-5.55 GBq for adjuvant therapy, 5.55-7.40 GBq for therapy. The residual body radioactivity of patients was monitored at 24, 48 and 72 h after the administration of 131I by dynamic radiation whole-body scanner and compared among groups. All clinical data were reviewed to explore the factors associated with the residual radioactivity. Independent-sample t test, χ2 test and logistic regression analysis were used to analyze the data. Results:At 24 h after 131I therapy, the residual radioactivity of patients in FT group were significantly lower than those in RT group ((880.60±396.64) vs (1 022.31±503.94) MBq; t=-2.765, P=0.035). In FT group, the residual radioactivity of patients with 131I adjuvant therapy+ therapy at 24 and 48 h after 131I administration were higher than those with 131I ablation (24 h: (987.16±447.33) vs (766.27±277.87) MBq, 48 h: (233.47±146.52) vs (183.52±90.65) MBq; t values: -2.711 and -2.021, both P<0.05). In RT group, the residual radioactivity of patients with 131I therapy at 24, 48 and 72 h after 131I administration were (1 246.90±531.69), (244.57±131.35) and (90.65±67.37) MBq respectively, which were higher than those with 131I ablation ((715.50±300.07), (149.85±68.82) and (58.46±31.45) MBq; t values: from -3.822 to -2.682, all P<0.05). There were 17.4%(23/132; 10 patients in FT group, 13 patients in RT group) patients with residual radioactivity >400 MBq at 48 h after 131I treatment, and 100% (132/132) patients with residual radioactivity <400 MBq at 72 h after 131I treatment. T staging, N staging, stimulated thyroglobulin level, and 131I dosage were significant factors affecting the residual radioactivity of patients ( t values: from -2.562 to 4.211, χ2 values: 3.988-8.332, all P<0.05), and T staging and 131I dosage were independent factors ( Walds values: 4.253-14.035, all P<0.05). Conclusions:The residual radioactivity of patients at 24 h after 131I treatments is higher than 400 MBq and hospital isolation time should be appropriately controlled. At 72 h after 131I treatment, the residual radioactivity of patients meets the national standard of discharging hospital. The residual radioactivity of patients with more advanced T staging and 131I dosage (>5.55 GBq) may not reach the standard at 48 h after 131I therapy, and the isolation time should be extended to 72 h.