CT3N0 rectal cancer: Potential overtreatment with preoperative chemoradiation (CRT) is warranted

Abstract

3568 Background: Although CRT has emerged as the preferred treatment for T3 and/or lymph node (LN) positive rectal cancer, Sauer et al (NEJM 2004) demonstrated that 18% of patients deemed suitable for preop CRT via endorectal ultrasound (ERUS) were overstaged and therefore received unnecessary preoperative CRT. Since data also suggest that LN negative rectal cancer s/p TME may not need adjuvant therapy, it is reasonable to consider the omission of radiotherapy for the cT3N0 subset. We therefore determined the accuracy of pre-CRT ERUS/MRI staging in order to explore the validity of a non-radiation approach for cT3N0 disease. Methods: 188 ERUS/MRI staged T3N0 rectal cancer patients from 6 insitutions in the US, Europe and Asia received preoperative CRT (5-FU based and 45–52.5 Gy) followed by radical resection. Rates of pathologic complete response (pCR) and mesorectal LN involvement were determined. Results: Tumors were located a median of 5 centimeters from the anal verge. Sphincter-preserving surgery was performed in 135 (81%) patients. Overall pCR was 19%. Median number of LN sampled was 9 (range 0–38). Rate of positive LN was significantly associated with T-stage: pT0: 3%, pT1: 7%, pT2: 20%, pT3–4: 36%(p=0.001). 41 patients (22%) had pathologically positive mesorectal LN. There was no significant difference in rate of positive LN between those staged by ERUS and MRI(25% vs 16%, p=0.19). Conclusions: Accuracy of preoperative ERUS/MRI for identifying mid to distal T3N0 rectal cancer is limited, as 22% will have undetected mesorectal LN involvement despite CRT. Therefore, ERUS/MRI staged T3N0 patients should continue to receive preoperative CRT. Although 19% are overstaged and therefore overtreated, our data suggest that an even larger number would be understaged and require postoperative CRT, which is associated with inferior local control, higher toxicity, and poor functional outcome. No significant financial relationships to disclose.