After a 28-day treatment break , maintenance bevacizumab ( 10 mg per kilogram intravenously every 2 weeks ) or placebo , plus temozolomide ( 150 to 200 mg per square meter per day for 5 days ) , was continued for six 4-week cycles , followed by bevacizumab monotherapy ( 15 mg per kilogram intravenously every 3 weeks ) or placebo until the disease progressed or unacceptable toxic effects developed .