Breast cancer screening through mammography has long been a cornerstone of early detection and mortality reduction. However, a recent study led by Dr. Yuqi Zhang and colleagues highlights a critical challenge: the occurrence of interval breast cancer (IntCa), which develops between scheduled mammography screenings and is often more aggressive.
Key Findings from the Study
This large-scale, population-based cohort study examined data from over 527,000 cancer-free women aged 40-74 in Stockholm, Sweden, between 1989 and 2020. Researchers found that while mammographic screening effectively detects many breast cancers (screen-detected breast cancer, ScrCa), a significant proportion—30%—are diagnosed as IntCa.
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Among the 29,049 women diagnosed with breast cancer in the study, 10,631 (2.0%) had ScrCa, while 4,369 (0.8%) had IntCa. The incidence of both ScrCa and IntCa has risen over time, but IntCa remains a major concern due to its potential aggressiveness and missed detection in standard screening protocols.
Risk Factors for Interval Breast Cancer
The study identified several factors that increase the likelihood of IntCa, including:
- Older Age at First Childbirth – Women who gave birth later in life had a higher risk.
- Higher Education Level – The association between education and increased IntCa risk remains complex and may reflect lifestyle or healthcare-seeking behaviours.
- Hormone Replacement Therapy (HRT) – Use of HRT was linked to a heightened risk of IntCa.
- High Mammographic Density – Denser breast tissue reduces the visibility of tumours on mammograms, making detection more difficult.
- Family History of Breast Cancer – Having a family history of breast cancer significantly raised the risk (HR 1.85; 95% CI 1.72-1.99), while a family history of IntCa increased the risk nearly threefold (HR 2.92; 95% CI 2.39-3.55).
- Estrogen Receptor (ER)-Negative Cancers – Women with IntCa were more likely to have ER-negative cancers compared to those with ScrCa (22% vs 11%), indicating a more aggressive cancer type.
Implications for Breast Cancer Screening
Despite widespread adoption of age-based mammographic screening, the persistence of IntCa underscores the need for a more personalized approach. The study’s authors advocate for risk-based screening strategies that consider individual risk factors, such as family history, mammographic density, and hormonal influences.
Moving Toward Personalised Screening
For healthcare providers, these findings reinforce the importance of discussing personalised screening plans with patients. While traditional mammography remains essential, supplemental imaging techniques—such as MRI or ultrasound—may be beneficial for high-risk individuals. Moreover, advancements in artificial intelligence for image analysis could help detect cancers that might otherwise be missed.
Conclusion
Interval breast cancer remains a pressing concern in breast cancer detection and management. This study provides compelling evidence that refining screening strategies to include risk-based assessments is critical to improving early detection and outcomes. Physicians should remain vigilant in identifying high-risk patients and advocating for enhanced screening protocols to bridge the gap in breast cancer detection.
Paper: Zhang, Y., et al. Incidence and Risk Factors of Interval and Screen-Detected Breast Cancer. JAMA Oncology. Original Investigation – ONLINE FIRST. Access online here.
