Adherence to guidelines and benefit of adjuvant radiotherapy in patients with invasive breast cancer: results from a large population-based cohort study of a cancer registry.

Purpose: According to German S3 guidelines, radiotherapy (RT) is indicated in patients with invasive breast cancer after breast-conserving therapy (BCT). The aim of this analysis was to assess adherence to guidelines, long-term survival, recurrence rates, and recurrence-free survival after adjuvant RT in patients with BCT in daily clinical practice.

Methods: This retrospective cohort study comprised data from the population-based clinical cancer registry of the Tumor Centre Regensburg (Bavaria, Germany). 6370 patients with non-metastatic invasive breast cancer and UICC tumor stages I, II, and III who were treated in certified breast cancer centers by BCT and diagnosed between 2003 and 2013 were included in the study.

Results: 6184 (97.1%) breast cancer patients received guideline concordant RT and showed a 3-year overall survival (OAS) of 96.8% in contrast to 90.9% in patients without RT (5-year OAS of 93.1% vs. 79.0%, p < 0.001). In multivariable Cox regression models, better overall survival was confirmed for the RT group (HR 0.64, 95% CI 0.46-0.88, p = 0.007). The 5-year local recurrence-free survival rate (RFS) in the irradiated patients was 92.1% vs. 62.0% in the comparison group (p < 0.001). The 10-year RFS was 80.5% vs. 36.0% (p < 0.001). This difference persisted after adjusting in multivariable analysis (HR 0.20, 95% CI 0.16-0.26, p < 0.001).

Conclusions: This population-based analysis showed that the implementation of German guidelines in clinical routine was successful and guideline concordant adjuvant radiotherapy after BCT leads to better overall and recurrence-free survival and lower local recurrence rates.