Supplementary Material for: Non-surgical site pain in women following breast cancer surgery: a systematic review and meta-analysis

Background: Chronic pain after breast cancer surgery affects up to 60% of patients. Evidence supports the fact that pain out-with the surgical site is a significant issue. This systematic review and meta-analysis sought to evaluate the prevalence of non-surgical site pain (NSSP) in women after breast cancer surgery at 6 months post-operatively. Methods: Adult women with a confirmed breast cancer diagnosis who had undergone breast cancer surgery were identified. The outcome pursued was pain out-with the surgical site measured on either NRS/VRS or VAS rating scale. CENTRAL, Embase, PubMed, MEDLINE, CINAHL, PsycInfo, Web of Science (WoS) and Scopus were searched to identify studies that examined NSSP after breast cancer surgery at 6 months. Data was gathered via pre-piloted Excel forms and analysed both quantitively and qualitatively. Meta-analysis was carried out using a random effects model to assess risk difference with 95% confidence interval (CI). Results: A total of sixteen studies were identified for inclusion. Eleven studies failed to provide sufficient data and consequently were analysed qualitatively. Five studies were adequate for quantitative analysis, including a total of 995 patients. Meta-analysis identified a risk difference of 18% (95%CI: 5 to 31%) between patients who had breast cancer surgery and a reference, however this is low quality evidence. Conclusion: This review has highlighted that breast cancer surgery increases the risk of pain out-with the surgical site post-operatively. It was additionally identified that NSSP data is often gathered in research yet rarely presented in results or highlighted as a primary outcome. As quality of evidence was low, research specifying NSSP as a primary outcome is required to provide more certainty.