Analysis on correlation of Tg with lesions counts ratio of ¹³¹I-WBS in DTC patients

Objectives To evaluate the correlation of thyroglobulin(Tg)with lesions radioactive counts ratio(R)of ¹³¹I-whole body scan(¹³¹I-WBS)in differentiated thyroid carcinoma(DTC)patients after ¹³¹I therapy and to provide reference index for judging recurrence and metastasis of DTC.

Methods 92 DTC patients undergone thyroidectomy and repeated ¹³¹I treatments(147times) during the period from 2011-01 to 2014-11 were enrolled.The materials such as scintigraphy imaging,clinical information,serum Tg levels during the same period were collected and analyzed.The oral doses of Na¹³¹I was 3.7-5.6GBq/times,then ¹³¹I-WBS was performed after 3-7days.By the use of regions of interest(ROI)on ¹³¹I-WBS image,¹³¹I-WBS total radioactive counts(T)was measured,the same as lesions(L),physiological uptake(P),bladder(B)and contaminated area(C).The result was calculated as R=L/(T-P-B-C).The patients were divided into six groups according to ¹³¹I therapy times,and the data were analyzed using SPSS V17.0.

Results The result of all 147 therapies was that the differences of Tg(χ²=14.842,P<0.05)and R(χ²=20.944,P<0.05)among six groups were significant,and that R has positive correlation with Tg(r_s=0.236,P<0.05).For the first three groups,R showed significant positive correlation with Tg (r₁=0.384,r₂=0.454,r₃=0.695,P<0.05).But for the last three groups,there was no correlation between R and Tg(P>0.05).Furthermore,after removing the 28 therapies which R and Tg are inconsistent(R+Tg- or R-Tg+),the remaining 119 therapies revealed that there was positive correlation between R with Tg(r_s'=0.329,P<0.001),and the results were similar with the above(group1-3:r₁'=0.424,r₂'=0.613,r₃'=0.644,P<0.05; group4-6:P>0.05).

Conclusions This study indicated that: 1.There was a positive correlation between Tg and R during the early stage,Tg combined with R is of important clinical value in monitoring recurrence and metastatic lesions. But after several times' treatments,R had no correlation with Tg,the clinical reference value declines.2.For the 28 therapies which R and Tg are inconsistent,they should be analyzed according to clinical setting.