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 outcome measures 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