Breast Neoplasms in Women Treated With X Rays for Acute Postpartum Mastitis. A Pilot Study

The incidence of benign and malignant breast tumors in 606 women treated with X rays for acute postpartum mastitis was determined by mail survey. The total cumulative X-ray doses per breast ranged from 75 R (air) to more than 1000 R. The follow-up period in most cases was from 10–25 years. Thirteen confirmed cases of breast cancer were observed instead of the 5.86 cases expected in a comparable group of women in the general population of upstate New York. In 5 of the 13 women with cancer, only one breast was treated; in each case, the cancer arose in the irradiated breast. Twenty-five surgically removed benign breast tumors were reported rather than the four to five cases expected. The incidence of benign tumors appeared to have increased in the untreated as well as in the treated breasts. There was no good evidence of a correlation between the dose and the incidence of malignant and benign tumors. Although a strong association is established between excess breast neoplasms and prior X-ray treatments for mastitis, lack of adequate control studies means that the radiation exposure per se cannot be implicated with certainty as an etiologic factor in the neoplastic transformation. Because irradiation is known to induce breast neoplasms in several species of animals and because of reports of excess breast neoplasms in women after exposure to ionizing radiation, it seems likely that the X-ray treatments were factors in the development of the excess breast tumors. We conclude therefore that at least some breast cancers in this series of women could have been induced by the prior X-ray exposures.