Relation of Pregnancies to Induction of Ovarian Tumors by X-rays

Abstract

Groups of female mice were exposed to 25-200 r of x-rays and mated with non-irradiated males. It was found that x-rayed mice can have one or several normal pregnancies and still be liable to the development of ovarian tumors in a stock in which this neoplasm is practically non-existant. Irradiation at 1-3 days of life with 150r sterilized only 1/3 of the mice while ovarian neoplasms appeared in about 76%. Irradiation at 1-3 days did not hasten the onset of ovarian neoplasms as compared to irradiation at 4-10 weeks. In both groups the tumors developed in middle aged and old mice. The growth rate of the tumors was likewise slow, hardly interfering with the normal life span of these animals. The factor of induction of ovarian tumors is discussed and it is postulated that a specific delayed x-ray effect coupled with a hormonal imbalance provoked by x-rays leads to their development.