New criteria for evaluating response in lymphoma clinical trials—RECIL 2017—have been developed by an International Working Group with the aim of harmonizing criteria with the Response Evaluation Criteria in Solid Tumors (RECIST). The new criteria were reported by Younes et al in Annals of Oncology.
The standard response criteria for lymphoma are the Lugano Criteria, based on [18F]2-fluoro-2-deoxy-D-glucose positron-emission tomography (FDG-PET) or bi-dimensional tumor measurements on computerized tomography (CT) scans. The RECIST are based on single-dimensional measurements.
A group of international lymphoma experts from academic centers and pharmaceutical companies, radiologists, and statisticians collaborated to harmonize lymphoma response criteria with RECIST, hypothesizing that single-dimension measurement could be used to assess response with results similar to those with standard criteria. The hypothesis was tested by analysis of 47,828 imaging measurements from 2,983 adult and pediatric lymphoma patients from 10 multicenter clinical trials. The resultant RECIL criteria were introduced at the International Workshop on Non-Hodgkin Lymphoma (San Diego 2016). The investigators found that assessment of tumor burden in lymphoma clinical trials can be performed using the sum of longest diameters of a maximum of three target lesions and that a novel provisional category of minor response warranted inclusion.
Elements of the RECIL response criteria are summarized/reproduced here.
Assessment of Tumor Burden
Assessment of tumor burden in lymphoma clinical trials can use the sum of longest diameters. In patients with disseminated disease, a maximum of three target lesions should be selected and used to estimate tumor response. Target lesions should be selected from those with the largest size that can be reproducibly measured and should preferably represent multiple sites or organs. In most cases, lymph nodes can be considered target lesions if the lymph node’s longest diameter is ≥ 15 mm.
Progressive Disease After Initial Response
After initial response, and in the absence of appearance of new lesions, progressive disease is defined as an increase of the nadir sum of diameters by > 20%.
Response Assessment in Patients Receiving Immune-Modulating Agents, Including Checkpoint Inhibitors
To account for potential ‘pseudoprogression,’ immune-related response criteria should be used, requiring confirmation of progressive disease on two consecutive scans at least 4 weeks apart and inclusion of new lesion measurements in the total tumor burden.
Appearance of New Extranodal Lesion
A minimum of 1 cm in largest diameter of new extranodal lesions is required to confirm progressive disease. New smaller but suspicious lesions should be designated as equivocal; if later confirmed (by CT or biopsy) as due to lymphoma, the documented date of disease progression should be the date of identification as equivocal.
The status of nontarget lesions should be taken into account before formulating the final response status. The International Working Group statement provides a recommended approach to response designation involving the best response of target and nontarget lesions.
Frequency of Response Assessment
In phase I/II clinical trials in previously treated patients, response should be assessed every 2 to 3 months during the first year of therapy. In the absence of new symptoms or clinical concerns, subsequent imaging studies can be carried out every 3 or 4 months during the second year, and every 6 months thereafter, for the duration specified in the clinical trial. Imaging assessment may be carried out less frequently during and after therapy of newly diagnosed patients and in the setting of randomized phase III studies.
The authors noted: “Future directions should evaluate the role of molecular depth of response (minimal residual disease and circulating DNA) in predicting treatment outcome, and to guide future studies aimed at evaluating shorter duration of therapy. Our new RECIL proposal should also be evaluated by the RECIST investigators to consider further harmonization of the criteria, with a special attention to the measurement of the long axis of lymph nodes, optimal number of target lesions, and introduction of [minor response] category.”
The work was supported by National Cancer Institute grants and a Leukemia and Lymphoma Society grant.
Anas Younes, MD, of Memorial Sloan Kettering Cancer Center, is the corresponding author of the Annals of Oncology article.
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