Tool to track target lesions over time and automatically classify treatment response according to RECIST 1.1.
RECIST (Response Evaluation Criteria in Solid Tumors) 1.1 is an internationally adopted set of rules for how to measure solid tumors on imaging and how to decide whether a patient is responding to treatment, has stable disease, or is progressing.
Only a limited number of clearly measurable "target" lesions are selected (up to 5 in total, maximum 2 per organ). For each of them the longest diameter is measured, and these diameters are summed to obtain a single value – the sum of longest diameters (SLD). This SLD is tracked over time across baseline, nadir, and current examinations.
Lesions that cannot be measured reproducibly, diffuse infiltrative changes, or small lymph nodes are usually classified as non‑target or non‑measurable disease. Their qualitative behavior (improvement, stability, clear worsening) is taken into account when assigning the final response category together with the change in SLD.
RECIST 1.1 defines strict thresholds for response: a ≥ 30% decrease in SLD compared to baseline is considered partial response, a ≥ 20% increase compared to the smallest recorded SLD (nadir) or the appearance of new lesions is considered progressive disease. Values between these thresholds are classified as stable disease, provided there are no new or unequivocally progressing non‑target lesions.
The goal of RECIST is to provide simple, reproducible and internationally comparable rules so that radiologists, oncologists and researchers speak the same language when reporting imaging‑based treatment response in clinical practice and clinical trials.