On the question of the reliability of criteria for the consistency of radioiodablation

SummaryThe article discusses the reasons for the possible ineffectiveness of radioiodablation in patients with differentiated thyroid cancer when using adequate individually calculated activities of 131I. Based on an analysis of post-therapeutic whole-body scintigraphy, laboratory parameters, dosimetric control and clinical manifestations after radionuclide therapy, significant criteria for the possible failure of standard combination therapy are identified and a change in treatment tactics in this group of patients is proposed.Purpose: search for the reasons of unsatisfactory results of radionuclide treatment in patients with differentiated thyroid cancer.Materials and Methods. We analyzed data for 2260 patients with differentiated thyroid cancer who received combined treatment with traditional preparation methods using thyrotropin alpha. From this cohort, a group of patients with an unexpected high 131I level at the pre-therapeutic stage was isolated against the background of the absence of early radiation complications and low dosimetry indicators. In patients, laboratory parameters of TSH, thyroglobulin and thyroglobulin antibodies were assessed with radioimmunoassay and clinical manifestations of radiation conditions, taking into account the prescribed therapy; the scintigraphy of the thyroid bed with 99mTc-pertechnetate, post-therapeutic scintigraphy with 131I upon exiting the "closed mode" and dosimetric monitoring with an assessment 48 hours after ingestion of therapeutic activity.Results. We analyzed the data of patients in whom there was a marked discrepancy between the usually interdependent results of scintigraphy before and after RIA, which subsequently changed the treatment tactics. A statistically significant difference was found between the selected groups in terms of the level of stimulated TSH (in patients with predictable (73.9 ± 31.8 mU/L) andunexpected (114.1 ± 30.5 mU/L) uptake of 131I ( P = 0.0218); by the values of the dose rate 48 hours after the intake of the calculated activity of 131I ( P = 0.000005). In addition, we analyzed the effect of traditional and drug methods of stimulating thyrotropinemia during preparation for radionuclide ablation. Thus, in patients with 4-week withdrawal of levothyroxine preparations and with the use of rhTSH, the TSH indicators were 80.7 ± 27 80.7 ± 27 mU/L and 123.3 ± 75.8 80.7 ± 27 mU/L, respectively ( P = 0.035), and the levels of stimulated TG were 10.2 ± 4.0 ng/ml and 3.2 ± 2.5 ng/ml (P = 0.041).Conclusion. The results show that the recommended empirical level of TSH > 30 mU/L is not synonymous with the activation of sodium iodine symporter and efficiency of RIA. It is possible to identify a group of patients with delayed/ partial activation of the symporter. To continue this study, we are going to change the protocol of preparation for radioiodablation and to find criteria of pre- therapeutic diagnosis for this group of patients.