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Detection Patterns of Breast Cancer Recurrence and Contralateral New Primaries in a Large Integrated Health System
Ali M Duffens1, Cecile A Laurent2, Isaac J Ergas2
11Kaiser Permanente Northern California, San Francisco Medical Center, San Francisco, CA.
Background:
Optimizing surveillance for the growing population of breast cancer survivors remains a challenge. Although screening guidelines for initial breast cancer are well established, current surveillance guidelines recommending routine provider examinations rely heavily on expert consensus rather than real-world data. Limited evidence exists on how second breast cancer events, including recurrences and contralateral new primary breast cancer, are actually detected in practice.
Methods:
We analyzed data from the Pathways Study, a prospective cohort of women diagnosed with stage I-III breast cancer at Kaiser Permanente Northern California between 2005 and 2013 and followed through 2021. We assessed the timing, outcomes, and detection modality of second events, categorized as patient-reported symptoms, surveillance mammogram, provider examination, incidental finding, or ancillary testing.
Results:
Of 4,417 eligible women, 792 (17.9%) experienced a second event: 577 (13.1%) had a recurrence and 215 (4.9%) developed a contralateral new primary. Most recurrences were metastatic (70.0%) and symptom-detected (78.0%), with only 9.9% found via surveillance mammogram and 5.0% by provider examination. In contrast, 82.8% of contralateral new primaries were detected via mammogram, with only 0.5% found on provider examination. Recurrences clustered within 5 years postdiagnosis and were associated with poor survival, whereas contralateral primaries occurred steadily over time with more favorable outcomes.
Conclusions:
In this large, diverse cohort with high access to survivorship care, routine provider examinations rarely detected second breast cancer events. Detection patterns differed by event type, with recurrences typically early, metastatic, and symptom-detected, whereas contralateral new primaries were found via imaging across the follow-up period. These findings support consideration of more individualized, risk-adapted surveillance strategies that emphasize symptom awareness, patient education, and appropriate use of imaging, rather than uniform examination-based approaches. Further research is needed to evaluate emerging tools, such as circulating tumor DNA and artificial intelligence, to improve the timely detection of second events and survivorship outcomes.
