Risk factors for circumferential R1 resection after neoadjuvant radiochemotherapy and laparoscopic total mesorectal excision: a study in 233 consecutive patients with mid or low rectal cancer

This study aimed to identify risk factors for circumferential R1 resection (R1c) after neoadjuvant radiochemotherapy (RCT) and laparoscopic total mesorectal excision (TME) for mid or low rectal cancer. Better knowledge of pre- or intraoperative risk factors could possibly help for the management of these patients. Between 2005 and 2013, 233 consecutive patients undergoing laparoscopic TME for low or mid rectal cancer after RCT were included. R1c resection was defined as a circumferential margin a parts per thousand currency sign1 mm. Univariate and multivariate analyses were performed to identify independent risk factors for R1c. Twenty-five patients had R1c resection (11 %). In univariate analysis, low rectal cancer, anterior tumour, T4 on pretherapeutic magnetic resonance imaging (MRI), T4 and/or N+ on post-RCT MRI and operative time > 240 min were associated with a significantly increased risk of R1c resection. In multivariate analysis, only T4 on post-RCT MRI (odds ratio (OR) = 6.02 [1.06-33]; p = 0.043) and operative time > 240 min. (OR = 5.4 [1.01-28.9]; p = 0.049) were identified as independent risk factors for R1c resection. The risk of R1c resection was 3 % (n = 3/88), 10 % (n = 5/51) or 38 % (n = 3/8) when 0, 1 or 2 risk factors were present in the same patient, respectively. Patients with T4 on MRI after RCT and/or operative time > 240 min. seems to be at higher risk for R1c resection. In a pragmatic approach, we consider that systematic second MRI after RCT could help the surgeon, especially in area where circumferential margin is too short, in order to reduce this risk of R1 resection.