PILOT-STUDY OF ENHANCEMENT OF CISPLATIN ACTIVITY BY HIGH-DOSE CYTARABINE IN ADVANCED GASTRIC AND COLORECTAL (G3 G4) CANCER/

The response rate of advanced gastric cancer to cisplatin monotherapy averages 20% and in colorectal cancer no activity of cisplatin monothe rapy has been detected in initial studies. Cytarabine is ineffective i n gastic cancer and displays borderline activity in colorectal cancer. In vitro studies on cell lines from human digestive cancers have demo nstrated a dose and timing dependent enhancing effect of cytarabine on cisplatin antitumor activity. The aim of the present study was to inv estigate whether this enhancing activity can also be demonstrated in v ivo. We have treated 37 patients with advanced gastrointestinal cancer (21 gastric and 16 colorectal), poorly differentiated G3-G4. The trea tment included - Day 1: cytarabine 500 mg/m(2) 0 h and 12 h, cisplatin 15 mg/m(2) 6 h and 18 h. Day 2-4: cisplatin 30 mg/m(2). Cycles were r epeated every 4 weeks. Thirty four patients were evaluable for objecti ve response. The overall response rate was 16.7% (CR 2/18, PR 1/18, SD 5/18, PD 10/18) for patients with gastric cancer and 25% (CR 1/16, PR 3/16, SD 7/16, PD 5/16) for patients with colorectal cancer. Grade 4 anemia (WHO criteria) occurred in 1/37 and thrombocytopenia in 1/37 pa tients. These patients had previous adjuvant chemotherapy. Vomiting gr ade 3 occurred in 4/37 and hepatotoxicity grade 3 in 1/37 patients. Th ere were no toxic deaths. Our study did not demonstrate any enhancemen t of cisplatin activity by high dose cytarabine in advanced gastric ca ncer. There appears to be an enhancing activity on colorectal cancer a lthough true synergism can not be ruled out since cytarabine has a bor derline activity in this type of human cancer.