A new study suggests that mesothelioma doctors may be at a disadvantage when it comes to accurately assessing how well patients are responding to treatment. To correct the problem, they are proposing changes in the standards by which mesothelioma tumors are measured.
A team of medical researchers in the U.S. and Australia examined the accuracy of the standard image-based method for assessing tumor progression and treatment response in mesothelioma. What they found is that the standard method may be off by as much as 34% when it comes to evaluating response and as much as 30% when assessing disease progression.
Currently, to decide what it means when a mesothelioma tumor grows or shrinks, doctors measure it using computed tomography (CT) scanning and compare changes in thickness to a modified version of the RECIST (Response Evaluation Criteria in Solid Tumors) protocol. Because mesothelioma tumors are shaped differently and grow differently than other solid tumors, doctors compare tumor thickness to a standard that is 30% less than the RECIST criteria for other solid tumors to determine partial response to treatment. Likewise, to evaluate whether mesothelioma is progressing (and predict a patient’s odds of survival), they compare tumor changes to a standard that is 20% higher than the RECIST criteria for disease progression in other solid tumors.
But the authors of the new study suggest that these modified criteria are still skewed when it comes to predicting survival in mesothelioma patients. To test their theory, they took CT scans of mesothelioma tumors at baseline and throughout treatment for 78 patients undergoing standard-of-care chemotherapy. They varied the response criteria for progressive disease (PD) and partial response (PR) in 1% increments to obtain what they called “optimized classification criteria”.
What they found is that the current RECIST criteria for mesothelioma correlate correctly with survival about 78% of the time. But when they modified the criteria to 64% less than the current standard for PR in solid tumors and 50% more than standard for PD in solid tumors, they were able to come up with a more accurate picture of mesothelioma patients’ health. Using these optimized criteria to evaluate mesothelioma CT scans, overall survival could be calculated with 85.5% accuracy.
“These criteria improve the correlation between image-based response and patient survival,” write the researchers in a summary of their findings.