Comparison of diameter and perimeter methods for tumor volume calculation

Purpose: Lesion volume is often used as an end point in clinical trials of oncology therapy. We sought to compare the common method of using orthogona l diameters to estimate lesion volume (the diameter method) with a computer -assisted planimetric technique (the perimeter method). Methods: Radiologists reviewed 825 magnetic resonance imaging studies from 219 patients with glioblastoma multiforme. Each study had lesion volume ind ependently estimated via the diameter and perimeter methods. Cystic areas w ere subtracted out or excluded from the outlined lesion. Inter- and intrare ader variability was measured by using multiple readings on 48 cases. Where serial studies were available in noncystic cases, a mock response analysis was used. Results: The perimeter method had a reduced interreader and intrareader var iability compared with the diameter method (using SD of differences): intra reader, 1.76 mt v 7.38 mt (P <.001); interreader, 2.51 mt v 9.07 mt (P <.00 1) for perimeter and diameter results, respectively. Of the 121 noncystic c ases, 23 had serial data. In six (26.1%) of those 23, a classification diff erence occurred when the perimeter method was used versus the diameter meth od. Conclusion: Variability of measurements was reduced with the computer-assis ted perimeter method compared with the diameter method, which suggests that changes in volume can be detected more accurately with the perimeter metho d. The differences between these techniques seem large enough to have an im pact on grading the response to therapy. J Clin Oncol 19:551-557. (C) 2001 by American Society of Clinical Oncology.