Drain‐free mastectomy and flap fixation: The interim analysis of a randomized controlled noninferiority trial

Flap fixation after mastectomy has proven to be one of the most promising solutions to reduce seroma formation. Drain placement remains standard practice in many clinics, even though this may be redundant after flap fixation.This is a prospective randomized controlled trial comparing mastectomy and wound closure using flap fixation with or without drain placement. The primary outcome measure was clinically significant seroma (CSS) incidence. The aim of this interim analysis was to assess the assumptions for the sample size calculation and to provide preliminary results.Between July 2020 and January 2023, 112 patients were included. CSS incidence was 9.1% in the drain group and 21% in the no-drain group. In total, 10 patients were lost to follow-up. These numbers are similar to the ones used for the sample size calculation. In the drain group, three patients required interventions for wound complications compared to nine in the no-drain group (odds ratio: 3.612 [95% confidence interval: 0.898-14.537]).The sample size calculation seems to be correct and no protocol amendments are necessary. Current preliminary results show no significant differences in CSS incidence. Complete results should be awaited to draw a well-powered conclusion regarding drain policy after mastectomy.