Modified RECIST (mRECIST)

Modified RECIST (mRECIST) is the standard way of measuring whether pleural mesothelioma is shrinking, stable or growing on CT scans. Because the tumor spreads as a sheet along the lining of the chest rather than forming a round lump, radiologists measure its thickness at set points instead of its diameter.

Origin

The RECIST rules (Response Evaluation Criteria in Solid Tumors), published in 2000, measure tumors by their longest diameter, which works poorly for rind-like pleural tumors. Australian researchers Michael Byrne and Anna Nowak published a modified version for mesothelioma in 2004, and an international group updated it as mRECIST 1.1 in 2018. A separate set of rules also called mRECIST is used for liver cancer.

Significance in Asbestos Context

Under mRECIST, the radiologist measures tumor thickness perpendicular to the chest wall or mediastinum at two points on each of three CT slices, and adds the measurements together. Comparing that sum over time gives the response categories used in clinical trials and many treatment decisions: a decrease of at least 30 percent is a partial response, an increase of at least 20 percent is progressive disease, and changes in between count as stable disease. New tumor deposits also count as progression. The method has limits: measurements vary between readers, fluid and scarring can be hard to tell from tumor, and immunotherapy can sometimes cause temporary swelling that looks like growth. For families, mRECIST explains the language in scan reports and trial results, such as stable disease or objective response rate, and helps with conversations about whether a treatment is working. Dated response assessments also document disease progression in a claim's medical timeline.

Example Sentence

The radiologist reported that the summed pleural thickness had fallen by 35 percent under modified RECIST, a partial response after four cycles of chemotherapy.

Related Terms

CT Scan, Clinical Trial, Disease Progression, Progression-Free Survival, Tumor Burden, Pleural Mesothelioma, Chemotherapy, Immunotherapy

Notes

• Ask your oncologist what stable disease or partial response means in your case.
• Ask whether each new scan is being compared with the same baseline scan.
• Keep copies of scan reports, and the images themselves, in date order.