Detección de daño cromosómico a corto plazo, debido a exposición terapéutica a ¹³¹I en pacientes con cáncer de tiroides

We evaluated the chromosomal aberration (CA) frequencies in the peripheral blood lymphocytes of ten female patients, age average 43.7 ± 12.9, with thyroid cancer (TC) who had been exposed to 100-200 mCi therapeutic doses of ¹³¹I. The blood samples were obtained before-treatment and at 2 and 24 h after-treatment. Radiation was measured in the samples by means of dysprosium-activated calcium sulfate thermoluminescent dosimetry. The maximum radiation levels were detected in the samples taken 2 h after treatment. A positive correlation was found between the sample-emitted radiation values and the frequencies of CAs (r = 0.495; p < 0.01). The average baseline frequency of aberrations found in the ten studied patients was 0.009 per cell. Upon application of the ¹³¹I therapeutic dose, this frequency increased to 0.04 and 0.02 CAs/cell at 2 and 24 h after-treatment, respectively (p < 0.05). Break-type aberrations experienced a peak at 2 h after-treatment, whereas rejoined aberrations, such as dicentrics, rings, and radial figures, increased with sampling time. Seven patients with metastases had high amounts of CAs at 2 and 24 h after-treatment, in comparison to three patients without metastases who had a lower frequency of CAs at 24h after-treatment. This difference could be due to the fact that circulating lymphocytes were exposed to a greater cancerous tissue mass, which retains ¹³¹I during the diagnostic and therapeutic processes. These results demonstrate the importance of detecting and surgically removing the largest possible amount of thyroid tissue in order to diminish the exposure of normal cells to radiation.