tokens: Thus , responses were classified as CR ( Complete Response , complete disappearance of all tumor lesions ) , PR ( Partial Response , reduction > = 50 % in the sum of all tumor lesions , calculated for each as the product of the largest diameter and the one perpendicular to it ) , PD ( Progressive Disease , increase in the diameter product of any individual tumor lesion by > = 25 % ) , and SD ( Stable Disease , anything between PR and PD ) .