Interval carcinomas in a breast cancer screening program (2007-2018): Characteristics and prognosis

Area of Science:

• Radiology
• Oncology
• Public Health

Background:

• Population-based breast cancer screening programs aim to detect cancers early.
• Interval cancers are those diagnosed between scheduled screenings.

Purpose of the Study:

• To analyze the radiologic and histologic characteristics of screening and interval breast cancers.
• To compare the stage and treatment of screening-detected versus interval cancers.

Main Methods:

• Analysis of 1395 screening-detected and 300 interval carcinomas from a population-based screening program (2007-2018).
• Digital mammography used every two years for women aged 50-69.
• Retrospective review of interval carcinomas, including radiologic findings, breast density, histology, phenotype, and surgical treatment.

Main Results:

• 52% of interval cancers were true interval cancers, 20.5% were false-negatives, and 13% showed minimal signs.
• Interval cancers were significantly more advanced (higher T-stage, greater axillary involvement) and aggressive (more HER2+ and triple-negative subtypes) than screening-detected cancers.
• A higher proportion of interval cancers (80%) were treated with mastectomy compared to screening-detected cancers (67%).

Conclusions:

• About 20% of interval cancers were evident on screening mammograms, often as asymmetry/mass.
• Interval cancers are diagnosed at a more advanced stage, necessitating mastectomy more frequently.
• Reviewing interval cancers is crucial for quality improvement in breast cancer screening programs.