Mammography screening is associated with more favourable breast cancer tumour characteristics and better overall survival: case-only analysis of 3739 Asian breast cancer patients.

Background: Early detection of breast cancer (BC) through mammography screening (MAM) is known to reduce mortality. We examined the differential effect that mammography has on BC characteristics and overall survival and the sociodemographic determinants of MAM utilization in a multi-ethnic Asian population.
Methods: This study included 3739 BC patients from the Singapore Breast Cancer Cohort (2010-2018). Self-reported sociodemographic characteristics were collected using a structured questionnaire. Clinical data were obtained through medical records. Patients were classified as screeners (last screening mammogram ≤ 2 years before diagnosis), non-screeners (aware but did not attend or last screen > 2years), and those unaware of MAM. Associations between MAM behaviour (MB) and sociodemographic factors and MB and tumour characteristics were examined using multinomial regression. Ten-year overall survival was modelled using Cox regression.
Results: Patients unaware of screening were more likely diagnosed with late stage (OR _{stage III vs stage I (Ref)} [95% CI]: 4.94 [3.45-7.07], p < 0.001), high grade (OR _{poorly vs well-differentiated (reference)} : 1.53 [1.06-2.20], p = 0.022), nodal-positive, large size (OR _{>5cm vs ≤2cm (reference)} : 5.06 [3.10-8.25], p < 0.001), and HER2-positive tumours (OR _{HER2-negative vs HER2-positive (reference)} : 0.72 [0.53-0.97], p = 0.028). Similar trends were observed between screeners and non-screeners with smaller effect sizes. Overall survival was significantly shorter than screeners in the both groups (HR _{non-screeners} : 1.89 [1.22-2.94], p = 0.005; HR _unaware : 2.90 [1.69-4.98], p < 0.001). Non-screeners and those unaware were less health conscious, older, of Malay ethnicity, less highly educated, of lower socioeconomic status, more frequently ever smokers, and less physically active. Among screeners, there were more reported personal histories of benign breast surgeries or gynaecological conditions and positive family history of breast cancer.
Conclusions: Mammography attendance is associated with more favourable BC characteristics and overall survival. Disparities in the utility of MAM services suggest that different strategies may be needed to improve MAM uptake.
(© 2022. The Author(s).)