Left-right breast asymmetry and risk of screen-detected and interval cancers in a large population-based screening population

Br J Radiol. 2020 Aug;93(1112):20200154. doi: 10.1259/bjr.20200154. Epub 2020 Jun 22.


Objectives: To assess the associations between automated volumetric estimates of mammographic asymmetry and breast cancers detected at the same ("contemporaneous") screen, at subsequent screens, or in between (interval cancers).

Methods: Automated measurements from mammographic images (N = 79,731) were used to estimate absolute asymmetry in breast volume (BV) and dense volume (DV) in a large ethnically diverse population of attendees of a UK breast screening programme. Logistic regression models were fitted to assess asymmetry associations with the odds of a breast cancer detected at contemporaneous screen (767 cases), adjusted for relevant confounders.Nested case-control investigations were designed to examine associations between asymmetry and the odds of: (a) interval cancer (numbers of cases/age-matched controls: 153/646) and (b) subsequent screen-detected cancer (345/1438), via conditional logistic regression.

Results: DV, but not BV, asymmetry was positively associated with the odds of contemporaneous breast cancer (P-for-linear-trend (Pt) = 0.018). This association was stronger for first (prevalent) screens (Pt = 0.012). Both DV and BV asymmetry were positively associated with the odds of an interval cancer diagnosis (Pt = 0.060 and 0.030, respectively). Neither BV nor DV asymmetry were associated with the odds of having a subsequent screen-detected cancer.

Conclusions: Increased DV asymmetry was associated with the risk of a breast cancer diagnosis at a contemporaneous screen or as an interval cancer. BV asymmetry was positively associated with the risk of an interval cancer diagnosis.

Advances in knowledge: The findings suggest that DV and BV asymmetry may provide additional signals for detecting contemporaneous cancers and assessing the likelihood of interval cancers in population-based screening programmes.

MeSH terms

  • Aged
  • Breast / diagnostic imaging*
  • Breast / pathology
  • Breast Density
  • Breast Neoplasms / diagnostic imaging*
  • Breast Neoplasms / pathology
  • Case-Control Studies
  • Cross-Sectional Studies
  • Early Detection of Cancer*
  • Female
  • Humans
  • Logistic Models
  • Mammography* / adverse effects
  • Middle Aged
  • Radiographic Image Interpretation, Computer-Assisted* / methods
  • Risk Factors
  • Time Factors
  • United Kingdom