Influence of tumour stage at breast cancer detection on survival in modern times: Population based study in 173 797 patients

Objectives: To assess the influence of stage at breast cancer diagnosis, tumour biology, and treatment on survival in contemporary times of better (neo-)adjuvant systemic therapy. Design: Prospective nationwide population based study. Setting: Nationwide Netherlands Cancer Registry. Participants: Female patients with primary breast cancer diagnosed between 1999 and 2012 (n=173 797), subdivided into two time cohorts on the basis of breast cancer diagnosis: 1999-2005 (n=80 228) and 2006-12 (n=93 569). Main outcomemeasures: Relative survival was compared between the two cohorts. Influence of traditional prognostic factors on overall mortality was analysed with Cox regression for each cohort separately. Results: Compared with 1999-2005, patients from 2006-12 had smaller (≤T1 65% (n=60 570) v 60% (n=48 031); P<0.001), more often lymph node negative (N0 68% (n=63 544) v 65% (n=52 238); P<0.001) tumours, but they received more chemotherapy, hormonal therapy, and targeted therapy (neo-adjuvant/adjuvant systemic therapy 60% (n=56 402) v 53% (n=42 185); P