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. 2021 May;3(3):e210008.
doi: 10.1148/rycan.2021210008.

A Primer on RECIST 1.1 for Oncologic Imaging in Clinical Drug Trials

Kathleen Ruchalski  1 , Marta Braschi-Amirfarzan  1 , Michael Douek  1 , Victor Sai  1 , Antonio Gutierrez  1 , Rohit Dewan  1 , Jonathan Goldin  1
Affiliations

A Primer on RECIST 1.1 for Oncologic Imaging in Clinical Drug Trials

Kathleen Ruchalski et al. Radiol Imaging Cancer. 2021 May.

Abstract

Drug discovery and approval in oncology is mediated by the use of imaging to evaluate drug efficacy in clinical trials. Imaging is performed while patients receive therapy to evaluate their response to treatment. Response criteria, specifically Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1), are standardized and can be used at different time points to classify response into the categories of complete response, partial response, stable disease, or disease progression. At the trial level, categorical responses for all patients are summated into image-based trial endpoints. These outcome measures, including objective response rate (ORR) and progression-free survival (PFS), are characteristics that can be derived from imaging and can be used as surrogates for overall survival (OS). Similar to OS, ORR and PFS describe the efficacy of a drug. U.S. Food and Drug Administration (FDA) regulatory approval requires therapies to demonstrate direct evidence of clinical benefit, such as improved OS. However, multiple programs have been created to expedite drug approval for life-threatening illnesses, including advanced cancer. ORR and PFS have been accepted by the FDA as adequate predictors of OS on which to base drug approval decisions, thus substantially shortening the time and cost of drug development (1). Use of imaging surrogate markers for drug approval has become increasingly common, accounting for more than 90% of approvals through the Accelerated Approval Program and allowing for use of many therapies which have altered the course of cancer. Keywords: Oncology, Tumor Response RSNA, 2021.

Keywords: Oncology; Tumor Response.

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Conflict of interest statement

Disclosures of Conflicts of Interest: K.R. disclosed no relevant relationships. M.B.A. disclosed no relevant relationships. M.D. disclosed no relevant relationships. V.S. disclosed no relevant relationships. A.G. disclosed no relevant relationships. R.D. disclosed no relevant relationships. J.G. Activities related to the present article: disclosed no relevant relationships. Activities not related to the present article: author is founder and board member of MEDQIA. Other relationships: disclosed no relevant relationships.

Figures

Baseline and follow-up CT images in a 55-year-old man with metastatic melanoma. CT imaging of the chest, abdomen, and pelvis was from A (left column), clinical trial enrollment and, B (right column), evaluation for treatment response at 9 months. At each time, the following were assessed: left lower lobe mass (row 1, top), right lower lobe nodule (row 2, middle), and subcarinal lymph node (row 3, bottom). The sum of diameters at baseline was 89 mm and at follow-up was 45 mm (a decrease of 49%), which was categorized as partial response. Dotted line represents the measured longest diameter of a lymph node. Solid line represents short-axis measurement.
Figure 1:
Baseline and follow-up CT images in a 55-year-old man with metastatic melanoma. CT imaging of the chest, abdomen, and pelvis was from A (left column), clinical trial enrollment and, B (right column), evaluation for treatment response at 9 months. At each time, the following were assessed: left lower lobe mass (row 1, top), right lower lobe nodule (row 2, middle), and subcarinal lymph node (row 3, bottom). The sum of diameters at baseline was 89 mm and at follow-up was 45 mm (a decrease of 49%), which was categorized as partial response. Dotted line represents the measured longest diameter of a lymph node. Solid line represents short-axis measurement.
Longitudinal response categorization. At each imaging time point, the patient will receive a single categorical response. When there is a partial treatment response (PR), the time point with the smallest tumor burden is the nadir (green arrow). Provided there are no changes in nontarget lesions and no new lesions, when the smallest tumor burden increases by more than 20% from nadir (or baseline [yellow arrow], if no nadir), this is the date of disease progression (PD) (red arrow). Lines on bottom images indicate tumor diameter.
Figure 2:
Longitudinal response categorization. At each imaging time point, the patient will receive a single categorical response. When there is a partial treatment response (PR), the time point with the smallest tumor burden is the nadir (green arrow). Provided there are no changes in nontarget lesions and no new lesions, when the smallest tumor burden increases by more than 20% from nadir (or baseline [yellow arrow], if no nadir), this is the date of disease progression (PD) (red arrow). Lines on bottom images indicate tumor diameter.
Overall response is the sum of the categorical responses of the target lesions, nontarget lesions, and presence or absence of new lesions. CR = complete response, NE = inevaluable, PD = progressive disease, PR = partial response, RECIST 1.1 = Response Evaluation Criteria in Solid Tumors version 1.1, SD = stable disease.
Figure 3:
Overall response is the sum of the categorical responses of the target lesions, nontarget lesions, and presence or absence of new lesions. CR = complete response, NE = inevaluable, PD = progressive disease, PR = partial response, RECIST 1.1 = Response Evaluation Criteria in Solid Tumors version 1.1, SD = stable disease.
Tumor tracker. Target lesion measurements and nontarget responses are collected in tumor trackers longitudinally to allow comparison of imaging response assessment for each patient over time.
Figure 4:
Tumor tracker. Target lesion measurements and nontarget responses are collected in tumor trackers longitudinally to allow comparison of imaging response assessment for each patient over time.
Overall survival. A patient receives multiple additional lines of treatment after their first therapy. In this case, overall survival is not a direct measure of treatment efficacy by therapy 1, as it also includes effects from therapies 2 and 3. PFS = progression-free survival.
Figure 5:
Overall survival. A patient receives multiple additional lines of treatment after their first therapy. In this case, overall survival is not a direct measure of treatment efficacy by therapy 1, as it also includes effects from therapies 2 and 3. PFS = progression-free survival.
Image-based surrogate outcome measures. Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1) categorical treatment responses inform several image-based surrogate outcome measures. The time point of progressive disease (PD) is used to determine both progression-free survival (PFS) and time to progression (TTP). Categorical responses of complete response (CR) and partial response (PR) will determine objective response rate (ORR).
Figure 6:
Image-based surrogate outcome measures. Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1) categorical treatment responses inform several image-based surrogate outcome measures. The time point of progressive disease (PD) is used to determine both progression-free survival (PFS) and time to progression (TTP). Categorical responses of complete response (CR) and partial response (PR) will determine objective response rate (ORR).
Time to progression (TTP) is the total time from which the patient starts treatment until radiologic disease progression. In this example, the patient’s tumor grew 20% from nadir, reaching disease progression. TTP was 54 weeks. SOD = sum of diameters.
Figure 7:
Time to progression (TTP) is the total time from which the patient starts treatment until radiologic disease progression. In this example, the patient’s tumor grew 20% from nadir, reaching disease progression. TTP was 54 weeks. SOD = sum of diameters.
Objective response rate reflects the degree of tumor shrinkage and is defined as the proportion of patients who experience a complete response (CR) or partial response (PR) while receiving treatment. A, A patient who underwent chest CT that revealed a single site of disease at baseline experienced, B, marked decreased size of the right paratracheal lesion, and thus is an objective responder. C, Objective responders are the percentage of patients with CR and PR. Arrow indicates the single site of disease, mediastinal lymphadenopathy. PD = progressive disease, RECIST 1.1 = Response Evaluation Criteria in Solid Tumors version 1.1, SD = stable disease.
Figure 8:
Objective response rate reflects the degree of tumor shrinkage and is defined as the proportion of patients who experience a complete response (CR) or partial response (PR) while receiving treatment. A, A patient who underwent chest CT that revealed a single site of disease at baseline experienced, B, marked decreased size of the right paratracheal lesion, and thus is an objective responder. C, Objective responders are the percentage of patients with CR and PR. Arrow indicates the single site of disease, mediastinal lymphadenopathy. PD = progressive disease, RECIST 1.1 = Response Evaluation Criteria in Solid Tumors version 1.1, SD = stable disease.
Duration of response (DOR) is defined as the time from initial response (partial or complete response) until the time of disease progression. In this example, the sum of diameters was less than 30% of baseline at week 18 (defined as partial response), and disease progression occurred at week 54. Therefore DOR was 36 weeks.
Figure 9:
Duration of response (DOR) is defined as the time from initial response (partial or complete response) until the time of disease progression. In this example, the sum of diameters was less than 30% of baseline at week 18 (defined as partial response), and disease progression occurred at week 54. Therefore DOR was 36 weeks.
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