Outline: This is a multicenter study. Subjects are stratified according to disease stage (IIIA vs IIIB or IV), response to prior treatment with front-line chemotherapy (stable disease vs partial response or complete response), prior treatment with front-line chemotherapy and radiotherapy (front-line chemotherapy with radiotherapy vs front-line chemotherapy alone), and prior treatment with front-line chemotherapy and other anticancer therapy (front-line chemotherapy with bevacizumab vs front-line chemotherapy alone or in combination with another anticancer agent). Subjects are randomized to 1 of 2 treatment arms.