Purpose: We have reported that gemcitabine and concurrent radiation is a promising therapy for patients with pancreatic cancer. We investigated whether the addition of cisplatin, which may increase the systemic efficacy of gemcitabine, would be synergistic with gemcitabine and/or radiation in human pancreatic cancer cell lines.
Methods and materials: BxPc3 and Panc-1 human pancreatic cancer cells were treated with three different schedules before radiation: (A) a sequential incubation of gemcitabine for 2 h followed by cisplatin for 2 h, (B) gemcitabine for 2 h, followed by washout of drug, replenishment of media for a 24-h incubation, followed by cisplatin for 2 h, and (C) gemcitabine for 24 h with a concurrent incubation of cisplatin for the last 2 h. Cells were assessed for clonogenic survival using a standard assay. Synergism was evaluated by the median effect analysis.
Results: The schedule shown to be maximally synergistic for both cell lines was the consecutive 2-h gemcitabine, 2-h cisplatin exposure, particularly at surviving fractions of <0.5. Cisplatin did not produce radiosensitization nor did it affect gemcitabine-mediated radiosensitization.
Conclusion: Cisplatin produces synergistic cytotoxicity with gemcitabine without compromising gemcitabine-mediated radiosensitization. On the basis of these laboratory and previous clinical observations, we have initiated a Phase I trial of cisplatin plus gemcitabine and radiotherapy in patients with unresectable pancreatic cancer.