Patients and Methods: Before systemic chemotherapy, the genetic expression of TS (TSmRNA level) was determined using a PCR method, Gene expression was calculated by determining the ratio between the amount of radiolabeled PCR product with the linear amplification range of the TS gene and the beta-actin gene. Chemotherapy consisted of two cycles of protracted infusion (PI) 5FU 200 mg/m(2)/d administered for 3 weeks with leucovorin 20 mg/m(2)/w. Cisplatin 100 mg/m(2) was administered on day 1.

Results: Sixty-five patients with primary gastric cancer had a median TS mRNA level of 4.6 x 10(-3) (range, 0.9 to 20.1 x 10(-3)). Thirty-five percent of patients had measurable responses in their primary tumors. The mean gastric cancer TSmRNA level in responding and resistant patients is statistically significant (P < .001), The median survival time was 43+ months for treated patients with TSmRNA levels less than the median and 6 months for those with TS m-RNA levels greater than the median (P = .003).

Conclusion: The genetic expression of TS (TSmRNA level) influences response to 5FU-based chemotherapy and survival for a cohort of patients with primary gastric cancer, Confirmation of these data could lead to therapeutic decisions based on specific molecular properties within a tumor.

(C) 1996 by American Society of Clinical Oncology.