Median progression-free survival among patients randomized to chemotherapy was 7 weeks ( 95 % CI , 4.3-8 .4 weeks ; median treatment duration , 8 weeks ; interquartile range [ IQR ] , 4.3-16 weeks ) and among those randomized to selumetinib was 15.9 weeks ( 95 % CI , 8.4-21 .1 weeks ; median treatment duration , 16.1 weeks ; IQR , 8.1-25 .3 weeks ) ( hazard ratio , 0.46 ; 95 % CI , 0.30-0 .71 ; P < .001 ) .