Table 4.

Overview of Response Criteria and Categories

	RECIST	mRECIST
Definition	Based on 1D measurement of tumor size [46].	Created to address the shortcomings of EASL (e.g. definition of target lesions)
	Allows for quantitative determination of changes in tumor burden in response to treatment.	Now endorsed by the European Association for the Study of the Liver (EASL) as the preferred method of assessing treatment response in HCC [48].
	Revised to RECIST version 1.1 in 2009 [47].
Concepts	Classifies lesions at baseline as “measurable” and “non-measurable” lesions. Measurable lesions: lesions that can be accurately measured in at least one dimension as >1cm. Non-measurable lesions: refer to all other lesions, including small lesions (longest diameter <1cm) and truly non-measurable lesions. Up to 5 Target lesions are allowed per patient (maximum of 2 lesions per organ). RECIST requires inclusion of the enhancing rim of the target lesion in the measurement. Non-target lesions include all other sites of disease and should also be recorded at baseline	Incorporates the concept of viable tumor [49].
		Integrates the RECIST definitions of response categories and target lesion selection into EASL.
		Uses 1D measurements of the viable component of the tumor (on CT or MRI) on arterial phase. Overall tumor burden (includes target lesions, non-target lesions and new lesions) is determined at the baseline image. Tumor response is then determined at each subsequent follow-up [49].
		Target lesion: 1) can be accurately measured in at least 1D as 1 cm or more, 2) shows intratumoral APHE on contrast-enhanced CT or MRI and 3) is suitable for repeat measurement.
	In patients with HCC and cirrhosis, certain unique considerations are required for assessment of tumor response in non-target lesions, for example, portal vein thrombosis.	Nontarget lesions: All other measurable lesions (not included as target lesions) should be identified as nontarget lesions and are recorded at baseline.
		Overall response is determined by combining the response of both target and non-target lesions.
Response Categories
Complete Response (CR)	Disappearance of all target lesions and non-target lesions.	Disappearance of any intratumoral APHE in all target and non-target lesions.
Partial Response (PR)	> 30% decrease in the sum of the longest diameter of target lesions.	≥ 30% decrease in the sum of diameters of viable target lesions.
Stable Disease (SD)	Neither sufficient shrinkage to qualify for partial response nor sufficient increase to qualify for progressive disease.	Any cases that do not qualify for either partial response or progressive disease.
Progressive Disease (PD)	> 20% increase in the sum of the longest diameter of target lesions, or the appearance of one or more new lesions. RECIST 1.1 additionally requires at least a 5 mm absolute increase in the sum of the longest diameters of target lesions to avoid measurement errors in small lesions.	≥ 20% increase in the sum of the diameters of viable target lesions or presence of one or more new lesions or unequivocal progression of existing non target lesions.

Note: RECIST = Response Evaluation Criteria in Solid Tumors, mRECIST = Modified response evaluation criteria in solid tumors, HCC = hepatocellular carcinoma, APHE = arterial phase hyperenhancement.