Comorbidity-dependent adherence to guidelines and survival in breast cancer-Is there a role for guideline adherence in comorbid breast cancer patients? A retrospective cohort study with 2137 patients.

In the treatment of breast cancer, decisions on adjuvant treatment reflect individual patient characteristics like age and comorbidity. This study assessed the association between adherence to guidelines for adjuvant treatment and survival while taking into account age at diagnosis and comorbidities. We collected the Charlson comorbidity index at baseline for 2179 women treated for primary breast cancer from 1992 to 2008 who participated in a German retrospective multicenter cohort study. We assessed subsequent adjuvant therapy guideline adherence and survival in relation to baseline comorbidities. Guidelines for adjuvant chemotherapy and radiotherapy were more often violated in patients with higher Charlson score. Patients with higher Charlson scores received chemotherapy and radiotherapy less often and had higher rates of mastectomy. Irrespective of comorbidity (Charlson score 0, 1-2, ≥3), patients with 100% guideline-adherent adjuvant treatment showed better overall and disease-free survival (DFS) compared to patients with guideline violations (GVs). Controlling for age, comorbidity and tumor characteristics, the hazard ratio for at least one GV was 1.65 (95% confidence interval [CI]: 1.33-2.07) for overall survival and 1.84 (95% CI: 1.53-2.22) for DFS. Guideline-adherent treatment was significantly less frequent in comorbid patients, although guideline adherence was strongly associated with improved survival, irrespective of severity, and number of comorbid diseases.