Radiosensitivity of human normal and tumoral thyroid cells using fluorescence in situ hybridization and clonogenic survival assay

Purpose: By using cell survival as a reference, we evaluated the radiosensi tivity of human normal and tumoral thyroid cells using of radiation-induced translocations. Methods and Materials: Tissue samples were obtained from patients undergoin g thyroidectomy, Cell cultures were established, irradiated with Co-60, and metaphases painted using commercial whole-chromosome 4 hybridization probe and pancentromeric probe. The clonogenic survival was assessed by conventi onal colony forming assay. Results: After irradiation, normal cultured thyroid cells yielded a higher number of translocations than cultures derived from adenomas or thyroid car cinoma. The colony forming assay demonstrated, by way of the mean inactivat ion dose, a higher survival of thyroid carcinoma and adenoma cells than of normal thyroid cells. This difference between tumoral and nontumoral cells is significant in each method (p = 0.0001), and cannot be explained by apop tosis in irradiated malignant cells. Correlation of the results obtained by both methods is shown by comparing the survival fraction at 2 Gy (SF2) and the percentage of chromosome 4 translocations at 2 Gy. Conclusion: These results indicate that the yield of radiation-induced tran slocations serves as a good and rapid prediction of the intrinsic radiosens itivity of thyroid cells, and that this test could be applied to other tumo rs, (C) 1999 Elsevier Science Inc.