Is it time to rethink the rule of total mesorectal excision? A prospective radiological and pathological study in 49 consecutive patients with mid-rectal cancer.

AIM: Total mesorectal excision (TME) after neoadjuvant chemoradiotherapy is the standard treatment for T3-T4 and/or N+ mid-rectal tumours, regardless of the exact tumour level. This leads to optimal oncological results but possible impaired functional results. Reducing rectal excision could reduce the functional drawbacks. This study prospectively assessed the risk of N+ or other mesorectal tumour deposit (OTD) below the tumour level by magnetic resonance imaging (MRI) performed after chemoradiotherapy and pathological examination of the TME specimen.

METHOD: Consecutive patients with mid-rectal cancer who underwent TME after chemoradiotherapy were included. A prospective evaluation by postchemoradiotherapy MRI and pathological examination was performed to assess the location of N+ nodes and/or OTDs.

RESULTS: Of 49 consecutive patients, 27 (55%) presented with nodes on postchemoradiotherapy MRI. However, only 12 nodes (size 2-4 mm) in 9 patients (18%) were under the tumour level. On pathological examination, 717 total lymph nodes were found, with 37 N+ and 22 OTD. According to the tumour level: (i) above tumour level, 21/453 nodes were N+ and 6 OTD; (ii) at tumour level, 16/166 nodes were N+ and 15 OTD; (iii) below tumour level, 0/98 nodes (0%) was N+ and only 1 OTD (2%) was noted at 2 cm below tumour level.

CONCLUSION: After chemoradiotherapy, N+ and/or OTD located under the level of the rectal cancer seems to be a very rare event. A postchemoradiotherapy MRI could help detect such patients. For others patients, conservation of the lower rectum with only a subtotal mesorectal excision could possibly improve function.