Table 1.

Criteria for evaluation of response by CE-CT vs. PET/CT

Response Category	Response Evaluation Criteria in Solid Tumors (RECIST 1.1)*[4]	PET Response Criteria in Solid Tumors (PERCIST)***[14]
Complete response (CR)	Disappearance of all target lesions	Disappearance of all lesions on PET images to background blood- pool levels, regardless of % change from baseline and anatomic size
	Reduction in short axis of target lymph nodes to < 10 mm
Partial response (PR)	≥ 30% decrease in sum of target lesion diameter sum	≥ 30% decrease in sum of target lesion SUL and 1 SUL unit absolute change
Progressive disease (PD)	≥ 20% increase in sum of target lesion diameter and minimum of 5 mm total increase	30% increase in sum of target lesion SUL and 1 SUL unit absolute change
	or new lesion	or new FDG avid lesion
	or unequivocal progression of non-target lesions**	or unequivocal progression of non-target lesion (e.g., ≥ 30% increase)
		or unequivocal progression by RECIST.
Stable disease (SD)	Does not meet other criteria	Does not meet other criteria

^*Measurements are based on the sum of the unidimensional measurement of the greatest diameter of a maximum of five lesions. The longest diameter with a minimum size of 1.0 cm was measured for a maximum of five target lesions (maximum of two lesions per organ). Lymph nodes were considered target lesions if ≥ 15 mm in short axis and only the short axis contributed to the baseline sum. Lesions < 10 mm or pathological lymph nodes ≥ 10 to < 15 mm short axis were considered non-measurable lesions. Other non-measurable lesions included leptomeningeal disease, ascites, pleural or pericardial effusion, inflammatory breast cancer, lymphangitic involvement of skin or lung, and lesions in a previously irradiated area. Bone lesions were not considered measurable unless a lytic lesion with an identifiable soft tissue component that met the aforementioned measurability requirements was present.

^**Defined as a substantial increase in overall disease burden even in the setting of SD or PR of target lesions. If the scan only showed non-measurable lesions, the criteria for progression would be defined as a substantial increase in disease burden.

^***The sum of all target lesions on baseline and follow-up scan was calculated and the percent change of the sum was used to determine response as defined by PERCIST criteria. Up to five target lesions (maximum of two lesions per organ) were determined based on the highest metabolic activity. A SULpeak below 1.5 × liver SUL + 2 standard deviations of liver SUL was required to qualify as a target lesion. All lesions other than the target lesion were considered non-target lesions without SULpeak cut-off. If patients only had lesions below the SULpeak cut-off, they could still be categorized as CR, PR, and PD if lesions completely disappeared, all lesions dropped by ≥30%, or at least one lesion increased by ≥30%. If the change was less than 30%, treatment response was assessed by RECIST 1.1.