Aggressive Intrinsic Subtypes in Breast Cancer: A Predictor of Guideline Adherence in Older Patients With Breast Cancer?

Background: Treatment side effects, comorbidities, and guideline-adherent treatment (GL+) influence the oncologic outcome of older breast cancer patients (oBCP) (age ≥ 70 years). The focus of this analysis was to investigate the associations among tumor characteristics, guideline adherence, and outcome and to compare these associations between younger breast cancer patients (yBCP) (age 50-69 years) and oBCP.

Methods: This is a retrospective multicenter cohort study with 17 participating certified breast cancer centers. The analysis of 10,897 patient records collected from 1992 to 2008 for GL+ and clinical outcome was performed. Tumor and patient characteristics and their associations with GL+ were compared between oBCP and yBCP.

Results: Nonguideline-adherent treatment (GL-) was associated with higher tumor stages and comorbidities. This effect was stronger in the oBCP group (P < .001). GL+ was significantly more common in yBCP than in oBCP (P < .001). The oBCP had significantly higher tumor stages, including tumor size (P < .001), nodal status (P < .001), and positive hormone receptors (P = .001). Tumor grading was lower (P = .001), and HER2neu overexpression was less frequent (P = .003) in oBCP. Overall survival and disease-free survival are significantly impaired if GL- occurred in patients with breast cancer independently of age.

Conclusions: GL- is associated with decreased disease-free survival and overall survival in both age groups. GL+ decreases advanced tumor characteristics in all age groups but significantly more in oBCP. If patients received GL+, we were unable to detect a statistical significant difference in the survival parameters.