Table 2. Errors in Response Evaluation Criteria in Solid Tumor Methodology Discovered at Quality Improvement Review.

Error Category	1st 6 Months n (%)	2nd 6 Months n (%)	P Value for Change
Baseline selection of lesions
Selection of target lesion when not unequivocally a metastasis	2 (3.8)	0 (0)	.15
Selection of too many target lesions at baseline	3 (5.7)	1 (1.2)	.30
Inappropriate selection of small lesions as target lesions	3 (5.7)	1 (1.2)	.30
Inappropriate selection of target lesion from within radiation field	2 (3.8)	0 (0)	.15
Reassessment of target lesions
Remeasurement of lesions in a different phase of contrast than baseline	2 (3.9)	0 (0)	.05
Failure to change measurement axis with changes in lesion orientation	1 (2.0)	0 (0)	.23
Reassessment of nontarget lesions
Premature assignment of PD for nontarget lesions	3 (5.9)	2 (1.2)	.08
Incorrect designation of PR for nontarget lesions	2 (3.9)	0 (0)	.05
Comparison to the incorrect prior scan	2 (3.9)	0 (0)	.05
Failure to assign CR for nontarget lymph nodes falling less than 10 mm	1 (2.0)	1 (0.6)	.40
Identification of new lesions
Premature assessment of new disease on anatomic imaging	2 (3.9)	0 (0)	.05
Premature assessment of new disease on FDG-PET studies	1 (2.0)	0 (0)	.23

CR, complete response; FDG-PET, 18-F-fluorodeoxyglucose positron emission tomography; PD, progressive disease; PR, partial response.

Note: Error frequencies for the first category are reported as percentage of baseline assessments. Error frequencies for the second through fourth categories are reported as percentages of follow-up assessments. Differences in error rates evaluated in Stata 13 (StataCorp LP, College Station, TX) using Fisher's exact test.