Oral topotecan given once or twice daily for ten days: a phase I pharmacology study in adult patients with solid tumors. - Gerrits CJ; Burris H; Schellens JH; Eckardt JR; Planting AS; van der Burg ME; Rodriguez GI; Loos WJ; van Beurden V; Hudson I; Fields S; Von Hoff DD; et al. (Clinical cancer research : an official journal of the American Association for Cancer Research, 1998)