Colorectal liver metastasis thymidylate synthase staining correlates with response to hepatic arterial floxuridine

We assessed whether intensity of colorectal liver metastasis staining with the thymidylate synthase (TS) antibody TS106 predicted response to hepatic arterial infusion (HAI) of floxuridine chemotherapy. Liver metastasis biopsies were taken during laparotomy for hepatic arterial cannulation and stained using the TS106 monoclonal antibody. Staining intensity was designated at histological examination by two independent assessors as either "high" or "low." Patients were treated by HAI, and liver metastasis response was assessed by comparison of computed tomography scan tumor volume before and after 4 months of treatment. A significant correlation (Fisher's exact test, P = 0.01) was noted between partial response to HAI and TS106 staining intensity in patients with colorectal liver metastases. Seventy-five percent of patients with evidence of a partial response had low TS staining compared with 29% of nonresponders. There was a significant difference (Fisher's exact test, P = 0.01) in the proportion of low (9 of 16) compared with high (3 of 20) TS staining tumors in which a partial response occurred. There was no significant difference (logrank test, P = 0.4) in survival from hepatic cannulation and HAI treatment of high (median, 322 days; interquartile range, 236-411) compared with low (median, 335 days; interquartile range, 301-547) TS staining patients. This study demonstrates an inverse correlation between TS immunohistochemical staining intensity in colorectal liver metastases and response to HAI. The results suggest that a prospective assessment of TS staining intensity in colorectal liver metastases would be useful to determine whether this method can be used to define patients who will benefit from HAI chemotherapy.