Model predicting the ypN0 status after good response to chemoradiotherapy in rectal cancer.

BACKGROUND: The purpose of this study was to identify the predictive factors for ypN0 status in tumors with good pathologic response to chemoradiotherapy (CRT). METHODS: A retrospective chart review was conducted on patients at two tertiary cancer center who underwent rectal resection after good response to CRT between 2000 and 2013. RESULTS: No preoperative treatment (oxaliplatin use, radiotherapy boost of 5,4 Gy, delay CRT-surgery) impacted on the ypN status. In the multivariate analysis, only a ypT<3 (HR 7.5 [2,9-19.5]) was significant and no lymphovascular invasion (HR 8,9 [1.6-49.8]) was limited to significance.The best model predicting the ypN0 status used only the ypT status<3. The major part (92.2%) of patients with ypT0-2 tumors had no LN invasion. CONCLUSION: The risk of lymph node involvement metastases was only 7.8% for the patients with an ypT0-2 status. A fullthickness transanal resection coud be the futur treatment of these patients.