Risk of contralateral breast cancer: associations with factors related to initial breast cancer

Am J Epidemiol. 1988 Aug;128(2):309-23. doi: 10.1093/oxfordjournals.aje.a114971.

Abstract

A case-control study was conducted to assess the risk factors associated with the development of a contralateral primary breast cancer among women who had had a first primary breast cancer. Hospital records were reviewed for 292 women who had an incident contralateral breast cancer, diagnosed in one of eight Connecticut hospitals between July 1, 1975 and December 31, 1983, and for a comparison group of 264 surviving unilateral breast cancer patients previously diagnosed in the same hospitals. All subjects were identified through the records of the Connecticut Tumor Registry. A family history of breast cancer in any first- or second-degree relative was associated with an almost threefold increased risk of developing a contralateral cancer (adjusted odds ratio (OR) = 2.8, 95% confidence interval (CI) = 1.6-4.9). Further, this relation was modified by the time elapsed since the initial cancer diagnosis (ratio of OR = 1.9, 95% CI = 1.2-3.0 for a five-year differential in time since initial diagnosis). A delay of 10 years in first full-term pregnancy was associated with a 36% decrease in risk (adjusted OR = 0.6, 95% CI = 0.3-1.2); this estimate excluded the magnitude of increased risk usually observed in studies of initial breast cancer. A conceptual framework is presented for assessing the study findings in the context of previous studies that have examined the corresponding associations for initial primary breast cancers.

PIP: To assess the risk factors associated with contralateral primary breast cancer among women who had a 1st primary breast cancer, the hospital records for 292 women who had an incident contralateral breast cancer diagnosed in a Connecticut hospital in 1975-83 were reviewed, as were records for 264 surviving unilateral breast cancer patients diagnosed earlier in the same hospitals. Both cases and controls were identified through the Connecticut Tumor Registry. The study findings suggest that both constitutional and environmental factors are associated with the risk of contralateral cancer. A family history of breast cancer in any 1st or 2nd-degree relative was strongly associated with the risk of a contralateral cancer (odds ratio, 2.8). This association was modified by the time elapsed since the initial cancer diagnosis (odds ratio, 1.9 for a 5-year differential in time since diagnosis). A woman with a 1st birth at 30 years of age was 36% less likely to develop a contralateral cancer than a woman whose 1st birth occurred at 20 years. Parity itself did not exert a significant influence on contralateral cancer risk. Also not associated with the risk of contralateral cancer were exogenous exposures to oral contraceptives, noncontraceptive estrogens, and cigarette smoking. Moreover, the age at which an initial cancer was diagnosed did not strongly influence the risk of a contralateral breast cancer. Further research is needed in this area since it is not possible from these findings to draw conclusions regarding whether the disease processes underlying the development of a contralateral primary breast cancer differ from those underlying the development of an initial breast cancer.

Publication types

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

MeSH terms

  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Body Constitution
  • Breast Neoplasms / genetics
  • Breast Neoplasms / pathology*
  • Contraceptives, Oral / administration & dosage
  • Female
  • Humans
  • Menarche
  • Middle Aged
  • Neoplasms, Multiple Primary*
  • Parity
  • Risk Factors
  • Smoking

Substances

  • Contraceptives, Oral