In 72 patients without occult neoplastic cells (ONCs) in their lymph node sinuses, the 5-year relapse-free survival (RFS) rate and overall survival (OS) rate were 71.3% and 69.2%, respectively. In 33 patients with ONCs, the 5-year RFS rate and OS rate were 33.9% and 31.3%, respectively. There was a marked difference of survival between the two groups (p=0.0001 and p=0.0003). The metastatic lymph nodes of the 33 ONC-positive patients had high and low levels of thymidilate synthase (TS) expression in 38.1% (8/21) and 61.9% (13/21) of the recurrence group (n=21), respectively, while high and low levels of dihydropyrimidine dehydrogenase (DPD) expression were found in 38.1% (8/21) and 61.9% (13/21), respectively. In the non-recurrence group (n=12), high and low levels of TS or DPD expression were detected in 58.3% (7/12) and 41.7% (5/12) versus 16.7% (2/12) and 83.3% (10/12), respectively. Patients with high TS and low DPD expression accounted for 9.5% (2/21) of the recurrence group and 50.0% (6/12) of the non-recurrence group (p<0.01). These results suggest that ONCs are clearly associated with the 5-year RFS and OS rates. Unlike the non-recurrence group, the recurrence group of ONC-positive patients with Dukes' C colorectal cancer is unlikely to respond well to treatment with 5-FU plus LV and require combination chemotherapy based on CPT-11 and/or L-OHP.

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