Background: While spin – i.e., a reporting practice that embellishes positive findings and understates negative ones – is prevalent in randomized controlled trials, it has yet to be investigated in the context of systematic reviews. Owing to their significant role in clinical decision making and patient outcomes, this study seeks to identify and evaluate the severity of spin in the abstracts of systematic reviews on breast cancer. Methods: We searched MEDLINE and Embase for systematic reviews and meta-analyses focused on breast cancer treatment, screening, and post-treatment quality of life between 1987 and 2020. Investigators independently screened for study selection, extracted spin data, and appraised the methodological quality of reviews using AMSTAR 2. In this cross-sectional study, 11,717 articles were identified, of which 581 met inclusion criteria. Following randomization, the first 200 were evaluated and 21 % contained evidence of at least one of nine types of spin. Results: We identified spin types one, three, four, five, and six but not two, seven, eight, or nine. In particular, pharmacological (AOR 4.36, 95 % CI [1.18–16.01]) and surgical (AOR, 10.10 95 % CI [1.60−63.68]) intervention-type studies were highly associated with spin. There were no other associations between study characteristics and spin. While these results are significant, they contain a wide confidence interval and the reader should draw conclusions accordingly. Conclusions: There is evidence of spin in meta-analyses and systematic reviews regarding breast cancer treatment and quality of life outcomes. Accordingly, readers of systematic review abstracts related to breast cancer could be misled by distorted presentation of findings. Policy summary: This study aims to improve the standards of reporting in systematic reviews and meta-analyses related to cancer.
- Breast cancer
- Systematic reviews