Survival of patients with bilateral versus unilateral breast cancer and impact of guideline adherent adjuvant treatment: A multi-centre cohort study of 5292 patients

This retrospective multi-centre study is focussed on recurrence free and overall survival of bilateral breast cancer (BBC) versus unilateral breast cancer (UBC). The impact of BBC on survival is stratified to guideline adherence, according to the German national S3-guideline. Another aim of the study is to identify the influence of various guideline violations in adjuvant treatment on survival of BBC patients. 229 (4.3%) patients had BBC and 5063 (95.7%) had UBC. There is a significant association between BBC/UBC and recurrence free (RFS: p < 0.001) and overall survival (OAS: p = 0.003). Only 15.7% of patients with BBC are treated 100% guideline adherent (index- + contralateral tumour). 31.0% (30.5%) were guideline adherent with respect to the index (contralateral) tumour. The outcome decreases significantly with the number of guideline violations. There was no significant difference in RFS and OAS between BBC and UBC after adjusting for tumour size, nodal status, grading and if guideline adherent treatment was applied.Conclusion1. Patients with BBC have primarily a worse prognosis in terms of RFS and OAS than patients with primarily UBC.2. There is a strong association between guideline adherence and RFS/OAS of patients with BBC or UBC. The outcome decreases with the number of guideline violations.3. If guideline adherent treatment was applied (for both tumours in case of BBC) there was no significant difference in RFS and OAS between BBC and UBC after adjusting for tumour size, nodal status, grading.