A multicentre Spanish study of 759 women diagnosed with breast cancer finds no consistent relationship between how closely women followed the cancer prevention recommendations of the World Cancer Research Fund (WCRF) and the American Institute for Cancer Research (AICR) and their mammographic density. The only signal seen — higher density among those who followed the recommendations better — appears to reflect less absolute breast fat rather than a higher carcinogenic risk.
What was known
Mammographic density is a well-known predictor of breast cancer risk and may be influenced by modifiable lifestyle factors. However, it was unclear how adherence to international prevention recommendations relates to that density.
What this work adds
The study analysed data from 759 breast cancer patients recruited at eight Spanish hospitals within the case-case Breast Cancer & Density Association Study. Participants completed an epidemiological questionnaire and a food frequency questionnaire. A standardised score was built to measure adherence to six WCRF/AICR recommendations. The percentage of mammographic density was measured with the validated DM-Scan software on the digital mammogram of the contralateral, tumour-free breast obtained before any treatment.
Main results
Overall, adherence to the WCRF/AICR recommendations was not consistently associated with mammographic density. However, the standardised prevalence of density of 50% or higher was greater among women with high adherence than among those with low adherence (standardised prevalence ratio 1.73; 95% CI 1.03-2.91). This positive association was especially evident with the physical activity recommendation (1.51; 95% CI 1.02-2.25).
What it means
The authors interpret this association as likely reflecting lower absolute breast adiposity — less fat in the breast — rather than a greater amount of fibroglandular tissue, and therefore not implying an increased cancer risk. The finding highlights the complexity of the relationship between lifestyle habits and breast tissue composition and cautions against simplistic readings of mammographic density as a stand-alone indicator.
Spanish context
The work sits within Spanish epidemiological research on breast cancer, with eight hospitals taking part, and draws on mammograms from routine care. It reflects the ability of Spanish groups to generate evidence on risk factors and prevention from real clinical cohorts.
Reference: Fernández-Morata J, Pollán M, Fernández de Larrea Baz N, Pachón-Olmos V, Ruíz-Moreno E, García-Pérez J, et al. Adherence to the WCRF/AICR cancer prevention recommendations and mammographic density. Breast Cancer Research, 2026. https://doi.org/10.1186/s13058-026-02304-w
