In multivariate analysis ( in 23 patients with RECIST SD ; median OS , 1.51 years ) , absolute change in mean positive pixels at spatial scaling filter of 4 mm , change in tumor size , and baseline serum lactate dehydrogenase ( LDH ) level were predictors of OS ( hazard ratio [ HR ] = 5.05 for decrease in mean positive pixels at spatial scaling filter of 4 mm vs increase , p = 0.007 ; HR = 4.14 for > 5 % increase in tumor size vs otherwise , p = 0.025 ; and HR = 1.29 for every 100 IU/L increase in baseline LDH level , p = 0.068 ) .