Response assessment in metastatic melanoma treated with ipilimumab and bevacizumab: CT tumor size and density as markers for response and outcome

Table 5 Summary of tumor response assessment and definitions for RECIST, Choi and MASS criteria

	RECIST	MASS	Choi
Measurements and lesion evaluations	Diameter^*1	Diameter	Diameter
		CT attenuation (HU)	CT attenuation (HU)
		Marked central necrosis^*2	CT attenuation (HU)
Response criteria ^*3	≥30% diameter decrease	≥20% diameter decrease, ≥40HU decrease, or marked central necrosis	≥10% diameter decrease, or ≥15% density decrease

*1: The longest diameters for non-nodal lesions and short axis for nodes were used according to RECIST1.1 [31]. This was applied to size measurement for Choi and MASS criteria in the present study.
*2: Marked central necrosis is defined as >50% of the enhancing central portion of a predominantly solid enhancing mass subjectively changing to near fluid attenuation (necrosis) after treatment [25].
*3: The sum of the diameters of all target lesions and the average of CT density measured in HU are used to assess response, comparing the values on the follow-up scan during therapy in reference to the values on the baseline pretherapy scan.