A case-control interview study of breast cancer among Japanese A-bomb survivors. II. Interactions with radiation dose

Cancer Causes Control. 1994 Mar;5(2):167-76. doi: 10.1007/BF01830263.


Three breast cancer risk factors were evaluated in terms of their interactions with radiation dose in a case-control interview study of Japanese A-bomb survivors. Cases and controls were matched on age at the time of the bombings and radiation dose, and dose-related risk was estimated from cohort rather than case-control data. Each factor--age at first full-term pregnancy, number of deliveries, and cumulative lactation period summed over births--conformed reasonably well to a multiplicative interaction model with radiation dose (the additive interactive model, in which the absolute excess risk associated with a factor is assumed to be independent of radiation dose, was rejected). An important implication of the finding is that early age at first full-term pregnancy, multiple births, and lengthy cumulative lactation are all protective against radiation-related, as well as baseline, breast cancer. Analyses by age at exposure to radiation suggest that, among women exposed to radiation in childhood or adolescence, a first full-term pregnancy at an early age following exposure may be protective against radiation-related risk.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adult
  • Age Factors
  • Aged
  • Breast Neoplasms / epidemiology*
  • Case-Control Studies
  • Cohort Studies
  • Dose-Response Relationship, Radiation
  • Female
  • Humans
  • Interviews as Topic
  • Japan / epidemiology
  • Lactation
  • Maternal Age
  • Middle Aged
  • Nuclear Warfare*
  • Parity
  • Postmenopause
  • Premenopause
  • Radiation Dosage*
  • Risk Factors
  • Survival