Adherence to breast cancer guidelines is associated with better survival outcomes: a systematic review and meta-analysis of observational studies in EU countries

Background: Breast cancer clinical guidelines offer evidence-based recommendations to improve the quality of health care for patients with or at risk of suffering breast cancer. Suboptimal adherence to breast cancer guideline recommendations has the potential to negatively affect population health. However, no study has systematically reviewed the impact of breast cancer guideline adherence -as a prognosis factor- on healthcare processes and health outcomes related to breast cancer. The objective of this systematic review is twofold: i) to analyse the impact of adherence to guidelines on health outcomes, and ii) to examine the extent to which adherence to guidelines impacts on health care costs. Methods: We searched for systematic reviews and primary studies in MEDLINE and Embase up to May 2019. Eligibility assessment, data extraction, and risk of bias assessment were conducted by one author and crosschecked by a second author. We used random-effects meta-analyses to examine the impact of adherence to guidelines on overall survival and disease-free survival, and assessed the certainty of evidence with the GRADE approach. Results: We included 21 primary studies. Most were published during the last decade (90%), followed a retrospective cohort design (86%), focused on adherence to treatment guidelines (95%), and were at low (80%) or moderate (20%) risk of bias. Nineteen studies (95%) examined the impact of guideline adherence on health outcomes, while two studies (10%) on healthcare cost. Adherence to guidelines was associated with increased overall survival (HR=0.66 (95% CI 0.58 to 0.75) and disease-free survival (HR=0.35 (95% CI from 0.15 to 0.82), representing 132 fewer deaths (168 fewer to 94 fewer) and 222 fewer recurrences (305 fewer to 55 fewer) per 1,000 patients at 5 years of follow-up (moderate certainty). Adherence to treatment guidelines was associated with higher costs, but adherence to follow-up guidelines was associated with lower costs (low certainty). Conclusions: There is moderate certainty that adherence to breast cancer guidelines is associated with an improved survival. Breast cancer guidelines should be rigorously implemented in the clinical setting.JRC.F.1-Health in Societ