Estimating age-specific breast cancer risks: a descriptive tool to identify age interactions

Cancer Causes Control. 2007 May;18(4):439-47. doi: 10.1007/s10552-006-0092-9. Epub 2007 Jan 9.

Abstract

Objective: Clarifying age-specific female breast cancer risks and interactions may provide important etiologic clues.

Method: Using a population-based case-control study in Poland (2000-2003) of 2,386 incident breast cancer cases and 2,502 control subjects aged 25-74 years, we estimated age-specific breast cancer incidence rates according to risk factors.

Results: Breast cancer risks were elevated among women with positive family history (FH), younger age at menarche, older age at first full-term birth, nulliparity, exogenous hormonal usage, and reduced physical activity (PA). Notwithstanding overall risks, we observed statistically significant quantitative (non-crossover) and qualitative (crossover) age interactions for all risk factors except for FH and PA. For example, nulliparity compared to parity reduced breast cancer risk among women ages 25-39 years then rates crossed or reversed, after which nulliparity increased relative risks among women ages 40-74 years.

Conclusion: Though quantitative age interactions could be expected, qualitative interactions were somewhat counterintuitive. If confirmed in other populations, qualitative interactions for a continuous covariate such as age will be difficult to reconcile in a sequential (multistep or monolithic) 'stochastic' breast cancer model. Alternatively, the reversal of relative risks among younger and older women suggests subgroup heterogeneity with different etiologic mechanisms for early-onset and late-onset breast cancer types.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Age Factors
  • Aged
  • Body Mass Index
  • Breast Neoplasms / epidemiology*
  • Case-Control Studies
  • Female
  • Hormone Replacement Therapy / statistics & numerical data
  • Humans
  • Incidence
  • Middle Aged
  • Motor Activity
  • Poland / epidemiology
  • Risk
  • Risk Assessment / methods*
  • Risk Factors