Long-term effects in skin and thyroid after radiotherapy for skin angiomas: a French retrospective cohort study.

To evaluate the long-term effects of skin angioma irradiation, a recall programme was established which included the systematic recalculation of the radiation dose to the skin and the thyroid. 22% of the 6229 patients contacted had a dermatological examination which revealed cutaneous dystrophy in 81% of the 1137 exposed angiomas and in 39% of the 208 unexposed angiomas. The risk of dystrophy (telangiectasia, hypopigmentation, superficial and subcutaneous atrophy) was 12.1 higher (P less than 0.0001) among patients who had received a surface skin dose above 30 Gy than among those who had received a dose of 10 Gy or less. The relative risk for each dystrophy component increased significantly (P less than 0.001) with surface skin dose. Furthermore, 14 basal cell carcinomas (BCC) were observed in 12 patients from the exposed group for all quantities of radiation, with a mean latency period of 22 years. No BCC was observed for a surface skin dose below 10 Gy. Thyroid testing was done on a subgroup of 431 patients whose thyroid gland had been particularly exposed during angioma irradiation. After recalculation, the dose delivered to the gland was below 1 Gy in 98% of patients. Only 13 thyroid nodules were discovered (1 hot and 12 cold). 1 patient with a cold nodule had a malignant thyroid tumour 21 years after irradiation. He belonged to the group of 7 patients who had received a thyroid dose above 1 Gy. Although no morphological abnormality was found in 98% of the tested patients, most (92%) had a thyroid iodine content below 15 mg (the standard French value), while a raised serum thyroglobulin level (greater than 30 ng/ml) was observed in 17%. This might confer a higher risk of subsequently developing thyroid nodules.