RECIST: Meaning in a Radiology Report

RECIST

Also written as: RECIST 1.1, Response Evaluation Criteria in Solid Tumors

RECIST is a set of rules for measuring whether solid tumors shrink, stay stable or grow on CT or MRI during cancer treatment.

Seen on: CT, MRI

How it reads in a report

Sum of target lesion diameters is 52 mm, down from 81 mm at baseline (36% decrease), a partial response by RECIST 1.1.

What it means

RECIST stands for Response Evaluation Criteria in Solid Tumors. On the first scan, before treatment starts, the radiologist picks up to five measurable tumors, at most two per organ. These target lesions are measured and their sizes added up. Each later scan measures the same lesions in the same way, so results stay comparable. Clinical trials rely on it for that reason. Other tumors are followed without exact measurements.

When it matters

The total gives one of four results. Complete response: all tumors have gone, and lymph nodes are back to normal size. Partial response: the total has shrunk by at least 30 percent from the first scan. Progressive disease: the total has grown by at least 20 percent, and at least 5 mm, from its smallest point. New tumors, or clear growth of the other tumors, also count. Stable disease: anything in between.

Questions to ask your doctor

Which lesions are being measured as my target lesions?
Is my result compared with my first scan or my smallest measurement?
Does stable disease mean my treatment is working?

General information, not medical advice. What a finding means for you depends on your symptoms, your history and the images themselves, so talk your results through with a doctor.