 This pilot phase II trial studies how well pemetrexed disodium works in treating patients with stage IV non-small cell lung cancer and an Eastern Cooperative Oncology Group ECOG performance status of 3. Performance status means how well patients are able to perform daily activities and care for themselves. Patients with a performance status of 3 have a limited ability to move around. Currently, only patients who are able to perform most of their daily activities may receive chemotherapy, due to the side effects it may cause. Pemetrexed disodium causes fewer side effects than many chemotherapy drugs and may help treat patients with stage IV non-small cell lung cancer and a lower performance status. 