T1166 ATP-Based Chemotherapy Response Assay Based Combination Chemotherapy for Unresectable Advanced Gastric Cancer: Interim Report of Prospective Controlled Study

Abstract

Background: Although, chemotherapy is one of the main treatment modalities for patients with unresectable advanced gastric cancer, it is difficult to find a universally applicable regimen. Recently, adenosine triphosphate based chemotherapy response assay (ATP-CRA) showed positive correlation with treatment response and survival in some human cancers. It is not certain whether this test can be applicable to gastric cancer, yet. Also, most studies used ATP-CRA on single anticancer drug while combination regimen is commonly used in practice.We prospectively conducted ATP-CRA based on doublet chemotherapeutic regimens in unresectable gastric cancer. Methods: Fifty-five patients with gastric cancer (with written informed consents) were consecutively enrolled between April 2007 and June 2009. ATPCRAs were tested to tumor cells obtained through endoscopic biopsy, using paclitaxel/ cisplatin [DDP], docetaxel/DDP, and irinotecan/DDP as well as single regimen including 5FU, cisplatinum, paclitaxel, docetaxel and irinotecan. All patients were randomly treated with one of above DDP-based doublet regimens into either tailored group where the doublet regimens showing the highest inhibition rate in ATP-CRAs using 3 combinations were administered, or empirical group where blindly chosen combinations were given regardless of ATP-CRA results. Results: The overall success rate of ATP-CRA was 96.4% (53/55). Evaluable thirty-two cases were analzyed (male:female=26:6, mean age: 57.9 years). Median follow up duration was 7.8 months (1.9-24.9). 18 cases and 14 cases were randomly assigned in tailored and empirical group, respectively. The disease control rate was 55.6% and 64.3%, respectively. The median progression-free survival (PFS) and overall survivals (OS) were 120 and 274 days, respectively in tailored group and 148 and 312 days in empirical group (p>0.05). Also, median PFS andOS inmatched group (where administered regimens included the drug with the highest inhibition rate in ATP-CRAs using paclitaxel, docetaxel and irinotecan, 10 cases) were 120 and 177days, respectively and 122 and 312days in unmatched group (remainings beside matched group, 22cases) (p>0.05). Conclusion: ATP-CRA was successfully performed with high success rate in gastric cancer with small amounts of tissue taken endoscopically. Prediction of response to combined chemotherapeutic agents by ATPCRA was not superior to that of empirical combined chemotherapy in advanced gastric cancer. A further study with larger number of patient will be required to confirm the clinical significance of combination chemotherapy assessed by ATP-CRA in unresectable gastric cancer.