The value of post-operative antibiotic therapy after laparoscopic appendectomy for complicated acute appendicitis: a prospective, randomized, double-blinded, placebo-controlled phase III study (ABAP study)

BACKGROUND: Approximately 30% of appendectomies are for complicated acute appendicitis (CAA). With laparoscopy, the main post-operative complication is deep abscesses (12% of cases of CAA, versus 4% for open surgery). A recent cohort study compared short and long courses of postoperative antibiotic therapy in patients with CAA. There was no significant intergroup difference in the post-operative complication rate (12% of organ/space surgical site infection (SSI)). Moreover, antibiotic therapy is increasingly less indicated for other situations (non-complicated appendicitis, post-operative course of cholecystitis, perianal abscess), calling into question whether post-operative antibiotic therapy is required after laparoscopic appendectomy for CAA. METHODS/DESIGN: This study is a prospective, multicenter, parallel-group, randomized (1:1), double-blinded, placebo-controlled, phase III non-inferiority study with blind evaluation of the primary efficacy criterion. The primary objective is to evaluate the impact of the absence of post-operative antibiotic therapy on the organ/space surgical site infection (SSI) rate in patients presenting with CAA (other than in cases of generalized peritonitis). Patients in the experimental group will receive at least one dose of preoperative and perioperative antibiotic therapy (2 g ceftriaxone by intravenous injection every 24 h up to the operation) and metronidazole (500 mg by intravenous injection every 8 h up to the operation) and, in the post-operative period, a placebo for ceftriaxone (2 g/24 h in one intravenous injection) and a placebo for metronidazole (1500 mg/24 h in three intravenous injections, for 3 days). In the control group, patients will receive at least one dose of preoperative and perioperative antibiotic therapy (2 g ceftriaxone by intravenous injection every 24 h up to the operation) and metronidazole (500 mg by intravenous injection every 8 h up to the operation) and, in the post-operative period, antibiotic therapy (ceftriaxone 2 g/24 h and metronidazole 1500 mg/24 h for 3 days). In the event of allergy to ceftriaxone, it will be replaced by levofloxacin (500 mg/24 h in one intravenous injection, for 3 days). The expected organ space SSI rate is 12% in the population of patients with CAA operated on by laparoscopy. With a non-inferiority margin of 5%, a two-sided alpha risk of 5%, a beta risk of 20%, and a loss-to-follow-up rate of 10%, the calculated sample size is 1476 included patients, i.e., 738 per group. Due to three interim analyses at 10%, 25%, and 50% of the planned sample size, the total sample size increases to 1494 patients (747 per arm). TRIAL REGISTRATION: Ethical authorization by the Comité de Protection des Personnes and the Agence Nationale de Sécurité du Médicament: ID-RCB 2017-00334-59. Registered on ClinicalTrials.gov (NCT03688295) on 28 September 2018.