Long-term prognosis of patients with pT1-2 colorectal cancer unaffected by lymph node metastasis

Background/Aim: Our goal was to investigate patients with pT1-2 colorectal cancer (CRC) in terms of lymph node metastasis (LNM) and its clinical implications, perhaps questioning the staging of such tumors. Patients and Methods: This retrospective cohort study took place at a high-volume cancer center in Japan. We stratified patients with pT1-2 CRC (n=1288) by presence (LNM+) or absence (LNM-) of LNM, assessing overall (OS), cancer-specific (CSS), and relapse-free (RFS) survival rates in both groups before and after propensity score matching (PSM). COX multivariate analysis served for screening of prognostic risk factors. Results: Lymph node metastasis was ultimately confirmed in 256 study subjects (19.9%). Before matching, tumors of the LNM+ (vs LNM-) group were more inclined to be fairly large (≥2 cm: 76.6% vs 61.2%; p <0.001), with greater propensity for infiltrating or ulcerative features (55.1% vs 36.2%; p <0.001) and histotypes of lesser differentiation (Mod/Poor/Sig/Muc: 65.6% vs 45.8%; p <0.001). Likewise, they showed greater tendency for aggressive growth (91.1% vs 81.1%; p <001), lymphatic (44.5% vs 19.4%; p <0.001) or vascular (59% vs 35.1%; p <0.001) invasion, and prolific lymph node harvesting (23.6±12.2 vs 21.7±12.3; p =0.025). Although similar in terms of OS (LNM-, 94.2%; LNM+, 91.8%; p =0.339), the LNM- (vs LNM+) group displayed significantly better CSS (99.5% vs 96.9%; p <0.001) and RFS (97.2% vs 89.5%; p <0.001). After matching, RFS still proved significantly better in the LNM- (vs LNM+) group (95.9% vs 89.8%; p =0.016), with multivariate analysis identifying LNM+ as an independent risk factor for RFS before and after PSM. A higher recurrence rate was also evident in the LNM+ (vs LNM-) group (before matching: 10.5% vs 2.8%, [ p <0.001]; after matching: 10.2% vs 4.1% [ p =0.008]), involving liver and lymph nodes primarily. Neither OS nor CSS differed significantly by group. Conclusion: In patients with pT1-2N+ CRC, we found greater risk of hepatic or nodal recurrence, compared with node-negative counterparts. However, long-term survival was unaffected. Appropriate downstaging of pT1-2N+ CRC from stage IIIA is therefore a reasonable prospect.