Is laparoscopic excision for superficial peritoneal endometriosis helpful or harmful? Protocol for a double-blinded, randomised, placebo-controlled, three-armed surgical trial

INTRODUCTION: Placebo-controlled surgical designs are recommended to ascertain treatment effects for elective surgeries when there is genuine doubt about the effectiveness of the surgery. Some elective surgeries for pain have been unable to show an effect beyond sham surgery, suggesting contributions from contextual factors. However, the nature of contextual factors in elective surgery is largely unexplored. Further, methodological difficulties in placebo-controlled surgical trials impact the ability to estimate the effectiveness of a surgical procedure. These include an overall lack of testing the success of blinding, absence of comparison to a no-surgery control group and dearth of test for neuropathic pain.For women with peritoneal endometriosis, there is uncertainty regarding the pain-relieving effect of surgery. Surgery may put patients at risk of complications such as postsurgical neuropathic pain, without guarantees of sufficient pelvic pain relief. The planned placebo-controlled trial aims to examine the effect of surgery on pelvic pain, widespread pain and neuropathic pain symptoms in women with peritoneal endometriosis, and to test the contribution of contextual factors to pain relief.

METHODS AND ANALYSIS: One hundred women with peritoneal endometriosis will be randomised to either diagnostic laparoscopy with excision of endometrial tissue (active surgery), purely diagnostic laparoscopy (sham surgery) or delayed surgery (no-surgery control group). Outcomes include pelvic pain relief, widespread pain, neuropathic pain symptoms and quality of life. Contextual factors are also assessed. Assessments will be obtained at baseline and 1, 3 and 6 months postrandomisation. Mixed linear models will be used to compare groups over time on all outcome variables.

ETHICS AND DISSEMINATION: The trial is approved by the Regional Ethics Committee in the Central Denmark Region (1-10-72-152-20). The trial is funded by a PhD scholarship from Aarhus University, and supported by a grant from 'Helsefonden' (20-B-0448). Findings will be published in international peer-reviewed journals and disseminated at international conferences.

TRIAL REGISTRATION NUMBER: NCT05162794.