MRI May Best CT for Assessing Mesothelioma Tumor Volume

By Will Boggs MD

November 09, 2020

NEW YORK (Reuters Health) - MRI offers advantages over CT for assessing primary-tumor volume in patients with mesothelioma, researchers from U.K. report.

"MRI measurements of tumor volume appeared more discriminatory in predicting subsequent survival than CT measurements of the same factor," Dr. Kevin G. Blyth of Queen Elizabeth University Hospital and the University of Glasgow, U.K., told Reuters Health by email. "We also observed that the volume of tumor seen using MRI was higher, which may explain this, as mesothelioma is known to be difficult to identify on CT."

Primary-tumor volume is a critical determinant of survival in malignant pleural mesothelioma (MPM). Tumor volume as assessed by CT is associated with overall survival, but CT volumetry is uncommonly used because of the laborious nature of the manual segmentation required.

Dr. Blyth and colleagues compared CT volumetry with a novel MRI volumetry protocol they developed for their study of 31 patients with a final diagnosis of MPM.

Using their MRI method, the mean analysis time was 14 minutes, the intraobserver agreement was 87.5%, and the interobserver agreement was 96.2%.

Mean CT analysis time was significantly longer (151 minutes), and interobserver agreement was only moderate (72%).

The mean primary-tumor volume was significantly higher by MRI (370 cc) than by CT (302 cc), and MRI tumor volumes were consistently larger than CT tumor volumes, the researchers report in Lung Cancer.

There was no correlation between either MRI tumor volume or CT tumor volume and clinical T-stage.

When dichotomized at 300 cc, higher MRI tumor volume was associated with a 4.03-fold greater risk of death, but there was no significant relationship between CT tumor volume at this cutpoint and overall survival.

"We need to look beyond traditional measures of tumor stage in mesothelioma and also look beyond CT imaging, which is the workhorse of chest radiology but has its limits," Dr. Blyth said.

"We need larger, multicenter validation studies to prove that the findings we report are reproducible," he said. "We are launching these now as part of the CRUK-funded PREDICT-Meso International Accelerator Network, of which I am chief investigator."

Dr. Blyth added, "We also need to complete large-scale studies to demonstrate that tumor volume (however you measure it) outperforms the currently used descriptors for T-stage (which don't account for volume or size - only the extent of invasion into adjacent structures)."

SOURCE: https://bit.ly/34EOfqf Lung Cancer, online October 1, 2020.

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