Clinical analysis of thyroid cancer in adult patients exposed to ionizing radiation due to the Chernobyl nuclear accident: 5-year comparative investigations based on the results of surgical treatment.

The aim of study was to compare clinical and pathologic findings of surgically removed thyroid tumors in adults with or without history of irradiation due to the Chernobyl accident. From 1990 to 2003, 2363 adults with no evidence of radiation influence in their history (group A) have undergone operation for thyroid nodules. During the same period, 311 patients (born before 1969) with strict evidence of Chernobyl irradiation also underwent operation (group B). Both groups were similar in age, sex, and preoperative examination. Group B represented three of the four official categories of people affected by the Chernobyl accident: 1-recovery operation workers; 2-people evacuated from the restricted area; 3-inhabitants of contaminated areas. The rate of thyroid carcinoma among all cases of thyroid nodules was significantly higher in group B--32.8% (102 patients) versus 27.2% (644 patients) in group A (p < 0.05). But a more distinct difference was observed in 1 and 2 categories of group B patients (the rate of cancer was, correspondingly, 54.8% and 47.8%;p < 0.01). The percentage of the invasive form of cancer (T4) was significantly higher in irradiated patients-39% versus 23% (p < 0.05) as were regional metastases (N1a,1b)--41% versus 19% (p < 0.01) and frequency of multifocality (33% versus 24%; p < 0.05). The most distinguished features were found in 1 category of group B: T4--in 47%, N1a-1b--in 62%, multifocality--in 41%. Our results suggest the irradiation as a cause of thyroid cancer in adult victims of Chernobyl and confirm the increasing aggressiveness of such tumors.