The significance of clinic-diagnostic factors in the course of estimation of side exposure of differentiated thyroid cancer patients after radioiodine therapy

The radioiodine therapy is the most well-known branch of radionuclide therapy. The therapy composed of thyroidectomy and iodine-131 radiopharmaceutical is the “gold standard” for treatment of differentiated thyroid cancer patients (DTC). Given metastases in lymph nodes such therapy is absolutely exclusive treatment mode. At the same time, despite the targeted effect of radioiodine on pathological foci a side internal exposure of healthy organs and tissues is noted in the course of radioiodine therapy. Therefore, a reliable assessment of the side exposure is necessary taking into account the individual characteristics of patients considering that the side dose varies significantly from patient to patient. For this reason, the identification of significance of personal clinic-diagnostic factors determined the side whole body exposure is the vital and important task. In this aspect, the cytogenetic examination of DTC patients by means of the analysis of chromosomal aberrations in peripheral blood lymphocytes is the goal of essential importance. The certain types of chromosomal aberrations are specific radiation markers that unequivocally indicate radiation exposure. Using the frequency of radiation markers the side absorbed dose can be reliably estimated. In the present work, the statistical analysis of the significance of various clinic-diagnostic factors in relation to the induction of radiation markers in the blood lymphocytes was performed. For that end the results of the cytogenetic examination of the group comprised of 38 DTC patients have been used. The examined patients underwent a course of radioiodine therapy in the department of radionuclide therapy of the A.F. Tsyb MRRC, Obninsk. The slide preparation and cytogenetic analysis were carried out in the laboratory of radiation cytogenetic of the same Center. The performed analysis of the correlation matrix with respect to the dependence of the increased frequency of stable and unstable markers resulted from a one-time course of radioiodine therapy showed no meaningfulness at the level R>0.3 for all the studied factors. For the absolute value of the frequency of radiation markers, both before and after radioiodine therapy, the meaningful relationship was found at the level R>0.7 for unstable and at the level R>0.8 for stable markers with a total administered activity of radioiodine during all the previous courses of radioiodine therapy.