Radiological imaging to assess disease status will be performed every 8 weeks ± 7 days (2 cycles) for 2 years and then every 4 months ± 1 month thereafter during the study until subjects develop radiographic disease progression per the modified RECIST criteria. In addition, any subject who discontinues study drug treatment prior to disease progression will continue to have radiological imaging performed every 8 weeks ± 7 days during the long term follow up period if the subject has not been in the study for 2 years until the subject develops radiographic disease progression or begins a new treatment. If the subject has been on study for 2 years, radiological imaging every 4 months ± 1 month will be performed during long term follow-up period until the subject develops radiographic disease progression or begins a new treatment.