Tumor response assessment by measuring the single largest lesion per organ in patients with advanced non-small cell lung cancer

• We compared tumor responses using RECIST 1.1 and modified RECIST in 64 NSCLC patients.
• The tumor responses showed good agreement between two criteria.
• Our result suggests that it might be possible to measure the single largest target lesion per organ.

BackgroundThe criterion of two target lesions per organ in the RECIST 1.1 is an arbitrary one, not being supported by any objective evidence. We compared tumor responses, respectively, using the RECIST 1.1 (measuring two target lesions per organ) and modified RECIST 1.1 (measuring the single largest lesion in each organ) in patients with advanced non-small cell lung cancer (NSCLC).Materials and methodsWe reviewed medical records of patients with advanced NSCLC who received a first-line chemotherapy between January 2004 and December 2013 and compared tumor responses according to the two criteria using computed tomography.ResultsA total of 64 patients who had at least two target lesions in any organ according to the RECIST 1.1 were included in the study. The differences in the percentage changes of the sum of tumor measurements between the RECIST 1.1 and mRECIST 1.1 were all within 10%. Thirty-three patients (51.6%) showed an increase in the absolute value of the percentage change when adopting the mRECIST 1.1, instead of the RECIST 1.1. The tumor responses showed high concordance between the two criteria (k = 0.899). Only three patients (4.7%) showed disagreement of the responses between the RECIST 1.1 and mRECIST 1.1. The overall response rates (20.3% vs. 20.3%) and disease control rates (89.1% vs. 90.6%) of first-line chemotherapy were not significantly different between the two criteria.ConclusionThe modified RECIST 1.1 was comparable to the original RECIST 1.1 in the response assessment of patients with advanced NSCLC. Our result suggests that it may be possible to measure the single largest target lesion per organ for evaluation of the best tumor response.