Rectal cancer

Abstract

When is the local recurrence risk low enough to refrain from the aim to prevent it?Local recurrence (LR) of rectal cancer is a devastating incident for each affected individual [2,21]. Thus, along with the attempt of improving survival, local tumor control has been an essential goal in the management of rectal cancer. Adjuvant radiotherapy (RT) with or without chemotherapy (ChT) reduced local recurrence and became a standard treatment in the 1980s [14], which was later on gradually replaced by preoperative RT (nRT) [9,45] or neoadjuvant radiochemotherapy (nRCT) [3,4,10,34,37]. Further substantial progress in terms of local recurrence reduction was achieved with the advent of quality-assured total mesorectal excision (TME; [15]). The next step was the introduction of magnetic resonance imaging (MRI) as a routine preoperative staging tool [1] facilitating the visualization of the distance between tumor and mesorectal fascia. If this distance is ≥1 mm on MRI, a negative circumferential resection margin (CRM) is assumed, provided that total mesorectal excision surgery is performed adequately. A negative CRM (defined as ≥1 mm on pathological work-up) has consecutively been identified and validated as an important surrogate parameter to predict the individual LR risk [12]. Results of the MERCURY study group (Magnetic Resonance Imaging in Rectal Cancer European Equivalence Study) whose authors propagated and investigated MRI-based treatment for rectal cancer were encouraging [23,43] and promoted similar attempts in the German-speaking community such as the OCUM study (optimized surgery and MRI-based multimodal therapy of rectal cancer). Preliminary results were recently published [22,42] and are commented in this editorial.Altogether, 230 patients with rectal cancer clinically staged as cT2-4, any cN, cM0 were included in this observational study. The anticipated CRM assessed by MRI (mrCRM) was used as a decision tool for selecting patients (n=230) either to undergo primary surgery (n=134) or to receive nRCT (n=96). For the lower third of the rectum (defined as <6 cm from the anal verge, 37%), nRCT was performed in all cT3 and cT4 tumors, irrespective of the anticipated CRM status; tumors of the middle third (i.e., 6 to <12 cm) were treated by nRCT in case of positive mrCRM only. For the upper third (12-16 cm), the decision was left to the discretion of the treating center. Clinically positive lymph nodes did not influence the choice of therapy; in patients with pathologically positive lymph nodes, chemotherapy was offered according to the standard of the respective centers. Postoperative RCT was restricted to patients with an involved CRM (pCRM ≤1 mm) [42].The mrCRM was positive in 74/230 patients, 72 in the nRCT group and 2 of the patients selected for surgery alone. A pathologically positive CRM (pCRM) occurred in 5.7% of all patients (nCRT: 11%, primary surgery: 1.5%). Pathology revealed complete remission (ypT0N0) after nRCT in 15% of patients, a partial remission in 67%. Even in patients whose margins were involv...