If a woman aged 35 years received a 0.01 Gy average breast dose from a mammographic examination, her lifetime risk of spontaneous breast cancer of about 7.58% might be expected to increase to 7.61%.

If on the other hand, one million women received the same dose, 234-425 excess breast cancers are estimated to develop during the lifetimes of these women as a result of this radiation exposure.

Age at irradiation has been found to be a major parameter of risk in epidemiological surveys. Women irradiated between ages 10 and 19 years of age were more susceptible than other ages. Data from the tuberculosis-fluoroscopy series suggest fractionating a large dose over many years does not mitigate the cancer risk.

Latency is apparently unrelated to dose. The minimal latent period in the two largest series of irradiated breast cancer cases was found to be about 5 years in women irradiated at age 30 year or over, with perhaps another 5 years required before the excess risk became substantial.

In younger women, the minimum latent period may be somewhat longer. Thereafter, the excess breast cancer response appeared steady until maximum follow-up, which ranged from 30-45 years in the various studies. Radiation-induced breast cancers in excessive numbers did not appear until the ages of high natural breast cancer risk. Thus, it seems prudent to assume a lifetime radiation risk for breast cancer induction from x-ray mammography.