Mammography screening tied to better breast cancer characteristics, outcomes

Regularly attending mammography screening sessions may lead to better breast cancer (BC) characteristics and help improve overall survival (OS), reports a recent Singapore study.

“Our observation that tumours detected among recent screeners have more favourable characteristics and confer better survival than tumours detected among nonrecent screeners and those unaware of screening suggests that early detection by mammography surveillance does show the benefit of picking up less advanced and less deadly cancers,” the researchers said.

Drawing from the 2010–2018 Singapore Breast Cancer Cohort, a total of 3,739 patients were enrolled, whose data were retrieved from their medical records. Those who had undergone mammography screening ≤2 years before diagnosis (n=1,089) were classified as screeners, while those who had skipped such screenings for >2 years were categorized as nonscreeners (n=2,260). Patients were also assigned to a third subgroup (n=390), comprised of those who were unaware of mammography.

Multinomial regression analysis revealed that compared with screeners, nonscreeners were significantly more likely to be diagnosed with later-stage cancers (stage II vs I: odds ratio [OR], 1.72, 95 percent confidence interval [CI], 1.46–2.02; p<0.001; stage III vs I: OR, 3.17, 95 percent CI, 2.52–3.98; p<0.001). [BMC Med 2022;20:239]

Similarly, high-grade tumours were nearly 60 percent more likely in nonscreeners (OR, 1.58, 95 percent CI, 1.26–1.97; p<0.001), as was a positive nodal status (OR, 1.61, 95 percent CI, 1.38–1.88; p<0.001). In addition, tumours >5 cm in size were more than thrice as likely to develop in nonscreeners vs screeners (vs ≤2 cm: OR, 3.22, 95 percent CI, 2.25–4.61; p<0.001).

In turn, nonscreeners also had worse 10-year OS. In Cox regression analysis adjusted for baseline patient characteristics, nonscreeners saw a nearly 80-percent higher risk of death than screeners (hazard ratio [HR], 1.77, 95 percent CI, 1.12–2.77; p=0.014). However, such an effect was attenuated after complete model adjustments.

Of note, the researchers found that outcomes were even worse for patients unaware of mammography. Stage II (OR, 2.72, 95 percent CI, 2.02–3.65; p<0.001) and III (OR, 4.95, 95 percent CI, 3.45–7.07; p<0.001) were strongly and significantly more likely to occur in this patient subgroup as opposed to screeners. The same was true for high-grade tumours (OR, 1.53, 95 percent CI, 1.06–2.20; P=0.022) and a positive nodal status (OR, 1.96, 95 percent CI, 1.52–2.52; p<0.001).

Ten-year OS was likewise worse in the mammography-unaware patients, with the risk of death being nearly thrice as high than in screeners in crude models (HR, 2.90, 95 percent CI, 1.69–4.98; p<0.001). However, any sort of confounder adjustment attenuated this interaction.

While the present findings highlight how important and beneficial mammography is for breast cancer, the researchers are quick to point out that “the nationwide screening mammography service is currently underutilized and various studies, including ours, looking into mammography screening behaviour have highlighted largely similar concerns and barriers to entry.”

In particular, a questionnaire administered upon study enrolment found that many patients did consider themselves to be at risk of breast cancer and opted to skip out on mammography. Others, meanwhile, were too afraid of results to get screened. On the other hand, important motivating factors that emerged were response to appropriate external cues to action and patients’ innate health consciousness.

“A shift in focus to how to tailor interventions to meet individual healthcare needs is needed to increase the number of breast cancers detected early and achieve positive health outcomes,” the researchers said.