Ramifications of lymph node metastasis in patients with pT1 colorectal cancer.

Background: The prognosis of stage IIIA colorectal cancer (CRC) is much better than stage II CRC in Japan. The purpose of this study was to investigate the implications of lymph node metastasis (LNM) in patients with pT1 CRC and to explore potential downstaging of pT1N1 CRC.

Methods: This retrospective cohort study was undertaken at a high-volume cancer center in Japan, grouping all eligible patients with radically resected pT1 CRC (n=723) according to presence (LNM+) or absence (LNM-) of LNM. We compared relapse-free survival (RFS) and cancer-specific survival (CSS) rates before and after propensity score matching.

Results: LNM was ultimately confirmed in 96 study subjects (13.3%). Ninety-two patients (95.83%) were N1 and only 4 (4.17%) patients were N2. Before matching, tumors of the LNM+ (vs. LNM-) group were bulkier (≥3 cm: 25.0% vs. 15.8%; P=0.03), with greater propensity for lymphatic (41.7% vs. 25.2%; P<0.001) or vascular (55.2% vs. 30.1%; P=0.004) invasion. Likewise, mean operative time (204.7±76.2 vs. 187.9±67.9; P=0.02) and hospital stay (10.47±9.449 vs. 8.32±7.029; P=0.03) tended to be lengthier. Although similar in terms of CSS (LNM+, 98.5%; LNM-, 99.0%; P=0.67), the LNM+ (vs. LNM-) group displayed significantly worse RFS (90.5% vs. 97.4%; P=0.004). After matching, neither RFS (94.8% vs. 90.2%; P=0.33) nor CSS (100% vs. 98.7%; P=0.23) differed significantly by group; and at no point (before or after matching) did LNM+ status emerge as an independent risk factor for RFS or CSS. Before matching, a higher recurrence rate was evident in the LNM+ (vs. LNM-) group (7.3% vs. 1.8%, P=0.001), but there was no difference in the matched groups.

Conclusions: LNM does not affect the long-term survival of patients with pT1N1CRC after radical resection. Appropriate downstaging from stage IIIA may be a reasonable prospect for pT1N1CRC with a low recurrence factor.