Dutch Reimbursement Lifts Gene Expression Testing to 37% but Leaves Two-Thirds of Eligible Breast Cancer Patients Untested

The IKNL–University of Twente implementation project now underway will map decision pathways and test audit-and-feedback interventions. If uptake reaches 60% by 2027, an estimated 800 additional women annually could avoid chemotherapy; failure to close the gap will sustain excess toxicity without survival benefit. Evidence quality is moderate: registry data provide population-level trends but lack granular comorbidity and patient-preference variables, requiring linked prospective cohorts to confirm causal effects of testing on outcomes.