Vintafolide is a drug that is specifically designed to enter cancer cells via the folate vitamin receptor (FR). Experimental evidence shows that this target receptor is expressed on a significant portion of non-small cell lung cancers. Early clinical evidence in a small number of Phase I patients suggests that vintafolide is generally well-tolerated, without many of the side-effects observed in more-standard therapeutic agents. This evidence suggests that vintafolide may be useful as a chemotherapy against progressive adenocarcinomas of the lung. The primary objective of this study is to collect data on clinical benefit produced by therapy with vintafolide .