Background Breast cancer (BC) clinical guidelines offer evidence-based recommendations to improve quality of healthcare for patients with or at risk of BC. Suboptimal adherence to recommendations has the potential to negatively affect population health. However, no study has systematically reviewed the impact of BC guideline adherence -as prognosis factor- on BC healthcare processes and health outcomes. The objectives are to analyse the impact of guideline adherence on health outcomes and on healthcare costs. Methods We searched systematic reviews and primary studies in MEDLINE and Embase, conducted in European Union (EU) countries (inception to May 2019). Eligibility assessment, data extraction, and risk of bias assessment were conducted by one author and crosschecked by a second. We used random-effects meta-analyses to examine the impact of guideline adherence on overall survival and disease-free survival, and assessed certainty of evidence using GRADE. Results We included 21 primary studies. Most were published during the last decade (90%), followed a retrospective cohort design (86%), focused on treatment guideline adherence (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 (10%) on healthcare cost. Adherence to guidelines was associated with increased overall survival (HR = 0.67, 95%CI 0.59–0.76) and disease-free survival (HR = 0.35, 95%CI 0.15–0.82), representing 138 more survivors (96 more to 178 more) and 336 patients free of recurrence (73 more to 491 more) for every 1000 women receiving adherent CG treatment compared to those receiving non-adherent treatment at 5 years 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 Our review of EU studies suggests that there is moderate certainty that adherence to BC guidelines is associated with an improved survival. BC guidelines should be rigorously implemented in the clinical setting. Trial registration PROSPERO (CRD42018092884).

Purpose Clinical guidelines' (CGs) adherence supports high-quality care. However, healthcare providers do not always comply with CGs recommendations. This systematic literature review aims to assess the extent of healthcare providers' adherence to breast cancer CGs in Europe and to identify the factors that impact on healthcare providers' adherence. Methods We searched for systematic reviews and quantitative or qualitative primary studies in MEDLINE and Embase up to May 2019. The eligibility assessment, data extraction, and risk of bias assessment were conducted by one author and cross-checked by a second author. We conducted a narrative synthesis attending to the modality of the healthcare process, methods to measure adherence, the scope of the CGs, and population characteristics. Results Out of 8137 references, we included 41 primary studies conducted in eight European countries. Most followed a retrospective cohort design (19/41; 46%) and were at low or moderate risk of bias. Adherence for overall breast cancer care process (from diagnosis to follow-up) ranged from 54 to 69%; for overall treatment process [including surgery, chemotherapy (CT), endocrine therapy (ET), and radiotherapy (RT)] the median adherence was 57.5% (interquartile range (IQR) 38.8-67.3%), while for systemic therapy (CT and ET) it was 76% (IQR 68-77%). The median adherence for the processes assessed individually was higher, ranging from 74% (IQR 10-80%), for the follow-up, to 90% (IQR 87-92.5%) for ET. Internal factors that potentially impact on healthcare providers' adherence were their perceptions, preferences, lack of knowledge, or intentional decisions. Conclusions A substantial proportion of breast cancer patients are not receiving CGs-recommended care. Healthcare providers' adherence to breast cancer CGs in Europe has room for improvement in almost all care processes. CGs development and implementation processes should address the main factors that influence healthcare providers' adherence, especially patient-related ones. Registration: PROSPERO (CRD42018092884). Keywords Breast neoplasms • Guidelines as topic • Evidence-based medicine • Guideline adherence • Systematic review Abbreviations CGs Clinical guidelines RT Radiotherapy CT Chemotherapy ET Endocrine therapy or hormonal therapy BCS Breast-conserving surgery MT Mastectomy ALND Axillary lymph node dissection TNBC Triple-negative breast cancer SLNB Sentinel lymph node biopsy HER2 Human epidermal growth receptor 2 Ena Niño de Guzmán and Yang Song have contributed equally to work and should be regarded as co-first authors.

Background Breast cancer clinical practice guidelines (CPGs) offer evidence-based recommendations to improve quality of healthcare for patients. Suboptimal compliance with breast cancer guideline recommendations remains frequent, and has been associated with a decreased survival. The aim of this systematic review was to characterize and determine the impact of available interventions to support healthcare providers’ compliance with CPGs recommendations in breast cancer healthcare. Methods We searched for systematic reviews and primary studies in PubMed and Embase (from inception to May 2021). We included experimental and observational studies reporting on the use of interventions to support compliance with breast cancer CPGs. Eligibility assessment, data extraction and critical appraisal was conducted by one reviewer, and cross-checked by a second reviewer. Using the same approach, we synthesized the characteristics and the effects of the interventions by type of intervention (according to the EPOC taxonomy), and applied the GRADE framework to assess the certainty of evidence. Results We identified 35 primary studies reporting on 24 different interventions. Most frequently described interventions consisted in computerized decision support systems (12 studies); educational interventions (seven), audit and feedback (two), and multifaceted interventions (nine). There is low quality evidence that educational interventions targeted to healthcare professionals may improve compliance with recommendations concerning breast cancer screening, diagnosis and treatment. There is moderate quality evidence that reminder systems for healthcare professionals improve compliance with recommendations concerning breast cancer screening. There is low quality evidence that multifaceted interventions may improve compliance with recommendations concerning breast cancer screening. The effectiveness of the remaining types of interventions identified have not been evaluated with appropriate study designs for such purpose. There is very limited data on the costs of implementing these interventions. Conclusions Different types of interventions to support compliance with breast cancer CPGs recommendations are available, and most of them show positive effects. More robust trials are needed to strengthen the available evidence base concerning their efficacy. Gathering data on the costs of implementing the proposed interventions is needed to inform decisions about their widespread implementation. Trial registration CRD42018092884 (PROSPERO)

No abstract