Abstract
AIM: To revisit the presumed relationship between tumour diameter and volume in advanced non-small-cell lung cancer (NSCLC) patients, and determine whether the measured volume using volume-analysis software and its proportional changes during therapy matches with the calculated volume obtained from the presumed relationship and results in concordant response assessment. MATERIALS AND METHODS: Twenty-three patients with stage IIIB/IV NSCLC with a total of 53 measurable lung lesions, treated in a phase II trial of erlotinib, were studied with institutional review board approval. Tumour volume and diameter were measured at baseline and at the first follow-up computed tomography (CT) examination using volume-analysis software. Using the measured diameter (2r) and the equation, calculated volume was obtained as (4/3)πr(3) at baseline and at the follow-up. Percent volume change was obtained by comparing to baseline for measured and calculated volumes, and response assessment was assigned. RESULTS: The measured volume was significantly smaller than the calculated volume at baseline (median 11,488.9 mm(3) versus 17,148.6 mm(3); p < 0.0001), with a concordance correlation coefficient (CCC) of 0.7022. At follow-up, the measured volume was once again significantly smaller than the calculated volume (median 6573.5 mm(3) versus 9198.1 mm(3); p = 0.0022), with a CCC of 0.7408. Response assessment by calculated versus measured volume changes had only moderate agreement (weighted κ = 0.545), with discordant assessment results in 20% (8/40) of lesions. CONCLUSION: Calculated volume based on the presumed relationship significantly differed from the measured volume in advanced NSCLC patients, with only moderate concordance in response assessment, indicating the limitations of presumed relationship.