BEST: Bypass equipoise sleeve trial; rationale and design of a randomized, registry-based, multicenter trial comparing Roux-en-Y gastric bypass with sleeve gastrectomy

Laparoscopic gastric bypass (LGBP) is a well-documented surgical intervention for severe obesity. Recently, laparoscopic sleeve gastrectomy (LSG) has gained increased popularity. Short-term follow-up in limited-sized randomized trials comparing LGBP and LSG show no major differences in weight-loss, adverse events, or effect on comorbidities; however, there is a lack of sufficiently powered, pragmatic, randomized controlled trials comparing the mid- and long-term results of the two methods. BEST is a randomized, registry-based, multicenter trial comparing LGBP and LSG. The trial has two primary outcomes; rates of substantial complications (SC) and total body weight loss. We hypothesize that patients treated with LSG will experience 35% fewer substantial complications during the 5-year follow-up compared to patients treated with LGBP, and that the efficacy of LSG will remain within a non-inferiority margin of 5% in terms of weight loss. Our sample size calculation, using data from the Scandinavian Obesity Surgery Registry (SOReg), shows a power of 80% for SC and > 95% for weight loss at p