To investigate thymidylate synthase (TS) expression in primary colorectal cancer (CRC) as a prognostic and predictive marker of benefit for adjuvant chemotherapy.

TS expression was immuno0histochemically (IHC) assessed on tumors from 1,389 patients with stage II and III CRC randomly assigned to either surgery alone or surgery plus 5−fluorouracil (5−FU)−based adjuvant chemotherapy.

In the subgroup treated with surgery alone (n=708), TS expression was prognostic using the classification of TS 0−1 versus 2−3 (p=0.045) as well as TS classified as 0−2 versus 3 (p=0.002). A high TS expression was associated with a shorter overall survival. Among patients with TS grade 3 (n=460), the subgroup treated with adjuvant chemotherapy had a significant longer OS (p=0.005).

In this study TS, immunohistochemically assessed, is a prognostic factor in CRC patients treated with surgery alone. Patients with the highest level of TS expression (grade 3) had an improved clinical outcome following adjuvant 5−FU−based chemotherapy.

PMID: 20332484 [PubMed − in process] Source: National Library of Medicine.