Methods of detecting and assessing functionally active folate receptors on tumors and treatment associated with those tumors are described. Also described are methods of selecting ovarian and lung cancer patients for therapy with a folate-vinca conjugate by identifying functionally active folate receptors on the tumors of the patient. Also described are methods and compositions for treating folate receptor expressing epithelial tumors with a folate-vinca conjugate in combination with doxorubicin such as pegylated liposomal doxorubicin in which the tumors include ovarian, endometrial or non-small cell lung cancer tumors, including platinum-resistant ovarian tumors and platinum sensitive ovarian tumors. Also described are methods of treating platinum-resistant ovarian cancer using a folate-targeted drug, in the absence or presence of selecting the patient by identifying functionally active folate receptors on the tumors of the patient.