Sentinel node detection after preoperative short-course radiotherapy in rectal carcinoma is not reliable

Background: Seninel node (SN) detection may be used in patients with colonic carcinoma. However, its use in patients with rectal carcinoma may be unreliable. To address this, SN detection was evaluated in patients with rectal carcinoma after short-course preoperative radiotherapy. Methods: Patent Blue V (1-2 ml) was injected peritumorally and submucosally directly after total mesorectal excision (TME) in 34 patients. The first one to four blue lymph nodes were categorized as SNs. All lymph nodes (non-SNs and SNs) were examined by conventional haematoxylin and eosin stained sections. If the SN was negative for metastasis, additional sections were immunostained with anticytokeratin CK7/8. In addition, SN detection was performed in 57 patients with colonic carcinoma. Results: A SN was identified in 26 of 34 patients with rectal carcinoma. In three the SN was the only positive lymph node. There were six false-negative SNs (sensitivity 40 per cent) and two patients were upstaged. By contrast, SN detection was possible in 56 of 57 patient with colonic carcinoma with a sensitivity of 90 per cent, and four patients were upstaged. Conclusion: The SN procedure for rectal carcinoma is not reliable in combination with TME and preoperative short-course radiotherapy.