LBA44 - Case fatality in breast cancer: Relative effect of attendance at breast screening and cancer treatment

Date 28 September 2014
Event ESMO 2014
Session Public health and health economics
Topics Breast Cancer
Cancer Aetiology, Epidemiology, Prevention
Presenter Nathalie Massat
Citation Annals of Oncology (2014) 25 (5): 1-41. 10.1093/annonc/mdu438
Authors N.J. Massat1, D. Tataru2, D. Parmar1, P.D. Sasieni1, S.W. Duffy1
  • 1Wolfson Institute Of Preventive Medicine, Centre for Cancer Prevention, Queen Mary University of London, EC1M 6BQ - London/GB
  • 2Knowledge And Intelligence Team (london), Public Health England, SE1 8UG - London/GB

 

Abstract

Aim

Invasive breast cancer is the second most common cause of cancer death among UK women. Although community breast screening has been shown to reduce breast cancer mortality, the relative effects of attendance at breast screening and improved treatment remain unclear.1 The aim of the study is to assess these relative effects on fatality from invasive primary breast cancer.

Methods

A matched case-control study within the English National Breast Screening Programme was set up in the London region.2 Cases of invasive primary breast cancer death in 2008-09 were matched 1:1 to controls with breast cancer diagnosed within 6 months prior to the case diagnosis (age 47-89), known to be alive at the case death, and matched for date of birth and area of residence. All had been invited to breast screening at least once prior to first diagnosis. Cases and controls were compared with respect to screening attendance by conditional logistic regression adjusted for pathology, and treatment within 6 months of diagnosis.

Results

The odds ratio (OR) for breast cancer fatality in women who attended at least one routine screen compared to never attenders was 0.41 (95% CI 0.30 - 0.55, p < 0.001) prior to adjustment, 0.70 (95% CI 0.49 - 1.02, p = 0.06), 0.45 (95% CI 0.33 - 0.63, p < 0.001) after adjustment for pathology and treatment, respectively, and 0.70 (95% CI 0.48 - 1.03, p = 0.07) after full adjustment. The risk of fatality decreased with time since last screen compared to no screening (OR = 0.64, 95% CI 0.44 - 0.93, p = 0.02; OR = 0.53, 95% CI 0.37 - 0.76, p < 0.001; OR = 0.22, 95% CI 0.15 - 0.31, p <0.001 for last attendance over 3 years ago, between 3 months and 3 years, or within 3 months, respectively). When adjusted for pathology, non-screen detected women who attended their last invitation (i.e. time since last screen between 3 months and 3 years) no longer showed a benefit from attending (OR = 0.88, 95% CI 0.57 - 1.36, p = 0.6). Additional adjustment for treatment had minimal impact on the estimate (OR = 0.92, 95% CI 0.58 - 1.44, p = 0.7). Collinearity between variables was judged to be negligible.3

Conclusions

In women diagnosed with breast cancer, attendance at breast screening remained a significant protective factor for fatality from the disease after accounting for pathology and treatment; adjusting for treatment had little impact on the estimate. Potential biases remain to be investigated.

Disclosure

All authors have declared no conflicts of interest.