Phase I, Dosage-finding and PK Study of IV Topotecan and Erlotinib With Refractory Solid Tumors

The primary objectives of this trial include: * To determine the maximum tolerated dosage (MTD) of intravenous topotecan when given in combination with oral erlotinib. * To define the dosage-limiting toxicities (DLT) of this combination. * To evaluate the pharmacokinetic (PK) parameters of intravenous topotecan with and without erlotinib The secondary objectives include: * To evaluate the pharmacodynamic effect of the topotecan and erlotinib combination * To evaluate for any correlations between the presence of CYP3A4/5 polymorphisms and topotecan / erlotinib disposition and to measure the frequency of MDR1 and BCRP in peripheral blood samples and correlate these results with topotecan pharmacokinetics * To measure the frequency of UGT genotypes in peripheral blood samples * To evaluate the objective response rate using the RECIST criteria.