Date Published: January 27, 2016
Publisher: Springer US
Author(s): Luc A. Heijnen, Doenja M. J. Lambregts, Max J. Lahaye, Milou H. Martens, Thiemo J. A. van Nijnatten, Sheng-Xiang Rao, Robert G. Riedl, Jeroen Buijsen, Monique Maas, Geerard L. Beets, Regina G. H. Beets-Tan.
Aim of this study was to evaluate the distribution of persistent mesorectal lymph node metastases on restaging MRI in patients with a good or complete response of their primary tumor (ypT0-2) after CRT for locally advanced rectal cancer.
Two hundred and twenty eight locally advanced rectal cancer patients underwent CRT, which resulted in a good response (downstaging to yT0-2) in 144 patients. Forty-nine patients were excluded (no surgery/insufficient follow-up or lacking lesion-by-lesion histology results). This resulted in a final study group of 95 yT0-2 patients. For the patients with a yN+-status, a detailed lesion-by-lesion comparison between restaging MRI and histology was performed to evaluate the characteristics and distribution of the individual N+-nodes.
7/95 patients (7%) had a yT0-2N+ status (11/880 (1%) N+ nodes): no N+ were found below the tumor level, 55% of the N+ nodes were located at the level of the tumor, and 45% proximal to the tumor (at a median distance of 1.4 cm above the tumor level). In axial plane, 82% of the nodes were located at the ipsilateral circumference of the tumor, at a median distance of 0.9 cm from the tumor/rectal wall.
The incidence of persistent metastatic mesorectal nodes after CRT in patients with a good tumor response after CRT is very low. No N+ nodes are found below the tumor level. All N+ nodes are located at the level of or proximal to the primary tumor, of which the majority very close to the tumor/lumen.
The results of our study show that the overall incidence of persistent positive lymph nodes in patients with locally advanced rectal tumors that have responded well and downstaged to yT0-2 after preoperative CRT is 7%; 6% for the complete responders (T0) and 10% for the patients with a small T1-2 residual tumor. No metastatic nodes were found distal to the tumor level; all persistent metastatic nodes were located at the level or proximal to the (former) tumor bed. Furthermore, the metastatic nodes were mainly located in the proximity of the tumor at the ipsilateral circumference.