New research led by an international team supported by the American Cancer Society (ACS) shows women with an increasing number of regular mammography screening exams prior to diagnosis of breast cancer considerably improved their probability of survival. The findings will be presented at this year’s annual meeting of the American Society of Clinical Oncology (ASCO) in Chicago, June 2-6. 

In this study, researchers, including presenting author Dr. Robert Smith, Senior Vice President, Early Cancer Detection Science at the American Cancer Society, analyzed incidence and survival data on 37,079 women ages 40-69 from nine Swedish counties who had between one and five invitations to screening and were diagnosed with breast cancer between 1992 and 2016. Of these, 4,564 subsequently died of breast cancer.

For each breast cancer diagnosed, scientists obtained data on previous screening history, and subsequent death (or not) from breast cancer.

Comparisons of survival with respect to numbers of screening exams attended prior to a diagnosis of breast cancer were carried out using Cox proportional hazards regression with time-varying covariates, i.e., cumulative numbers of screens, yielding hazard ratios, and 95% confidence intervals (CI). Study results were also corrected for potential self-selection bias, which gave a corrected estimate based on the proportion of participants, the uncorrected estimate, and the relative risk of breast cancer death for non-participants compared to an uninvited population.

The results showed, for a woman who participated in all five previous screening exams, the hazard of breast cancer death was 0.28 (95% CI 0.25-0.33, p<0.0001) [ 0.34 (95% CI 0.26-0.43, p<0.0001) after adjustment for self-selection], compared to a woman who had participated in none of the screening rounds.

For each number of invitations, the difference in survival by number of screening exams attended was progressively more favorable, and statistically significant (p<0.0001) in all cases compared to women participating in no screens.

Researchers noted the importance of regular participation in mammography screening should be clearly articulated in breast cancer screening messaging and decision aids.

This news release was published by the American Cancer Society on June 4, 2023.