Identifying recurrent breast cancer patients in national health registries using machine learning.

Background: More than 4500 women are diagnosed with breast cancer each year in Denmark, however, despite adequate treatment 10-30% of patients will experience a recurrence. The Danish Breast Cancer Group (DBCG) stores information on breast cancer recurrence but to improve data completeness automated identification of patients with recurrence is needed.
Methods: We included patient data from the DBCG, the National Pathology Database, and the National Patient Registry for patients with an invasive breast cancer diagnosis after 1999. In total, relevant features of 79,483 patients with a definitive surgery were extracted. A machine learning (ML) model was trained, using a simplistic encoding scheme of features, on a development sample covering 5333 patients with known recurrence and three times as many non-recurrent women. The model was validated in a validation sample consisting of 1006 patients with unknown recurrence status.
Results: The ML model identified patients with recurrence with AUC-ROC of 0.93 (95% CI: 0.93-0.94) in the development, and an AUC-ROC of 0.86 (95% CI: 0.83-0.88) in the validation sample.
Conclusion: An off-the-shelf ML model, trained using the simplistic encoding scheme, could identify recurrence patients across multiple national registries. This approach might potentially enable researchers and clinicians to better and faster identify patients with recurrence and reduce manual patient data interpretation.