Should pT2N+ Colorectal Cancer Be Downstaged from IIIA to IIA?

Abstract

This study investigated the significance of lymph node metastasis (LNM) in patients with pT2 colorectal cancer (CRC). This retrospective cohort study was conducted at a high-volume cancer center in Japan and targeted all qualifying patients (n=617) with radically resected pT2 CRC. Subjects were stratified by the presence (LNM+) or absence (LNM-) of LNM to compare cancer-specific survival (CSS) and relapse-free survival (RFS) rates before and after propensity score matching. There were 168 (27.2%) and 449 (72.8%) patients in the LNM+ and LNM- groups, respectively. Tumors in the LNM+ (vs. LNM-) group were more often less differentiated (Poor/Sig/Muc: 26.2% vs. 18.5%; p=0.035); more inclined to lymphatic (45.2% vs. 21.4%; p=0.000), vascular (64.9% vs. 44.8%; p=0.000), or neural (7.7% vs. 3.3%; p=0.019) invasion; and yielded more (≥12) harvested lymph nodes (94.0% vs. 85.5%; p=0.004). Although similar in terms of 5-year CSS (LNM-, 98.7%: LNM+, 95.8%; p=0.117), RFS in the LNM- (vs. LNM+) group was found to be significantly better (95.3% vs. 88.7%; p=0.003). After matching, RFS in the LNM- (vs. LNM+) group remained significantly better (95.4% vs. 88.7%; p=0.027). Recurrence was more likely in the LNM+ (vs. LNM-) group (pre-matching: 13.1% vs. 5.6%, p=0.002; post-matching: 12.4% vs. 5.2%, p=0.027), primarily occurring as liver metastases (pre-matching: 8.3% vs. 1.1%, p=0.002; post-matching: 7.8% vs. 1.3%, p=0.006). Lymph node metastasis does not affect CSS after radical resection of pT2 CRC, but vigilance for liver metastasis is essential. Downstaging of T2N+ CRC from stage IIIA to stage IIA is warranted.