RECIST response definitions

RECIST RESPONSE DEFINITIONS (V1.1)1

RECIST (Response Evaluation Criteria In Solid Tumours) v1.1 has now superseded RECIST v1.0. The key amendments are:
  • A maximum of five measurable non-nodal lesions should be measured, with a maximum of two per organ.
  • Lymph node measurement rules have changed.
  • The definition of progressive disease has changed.

MEASURABLE DISEASE:

  • Disease is measurable if there is at least one measurable target lesion. Target lesions should be selected on the basis of size and suitability for repeat measurement, up to a maximum of two measurable lesions per organ, and up to a maximum of five lesions in total. These should be representative of all involved organs.
  • Target lesion (non-nodal) must be accurately measurable in at least 1 dimension, with the longest diameter >10 mm (assuming CT slice thickness is no greater than 5mm). If the lesion is smaller than this then it is classed as non-measurable.
  • Measurements must be taken as close as possible to the beginning of treatment and never more than 5 weeks before the start of treatment. Target lesions should be assessed by CT, MRI or CXR, not by clinical assessment alone. The same imaging modality should be used throughout for any given patient.
    • When intra-venous contrast agents are given with CT, it is important to measure hepatic lesions in the same vascular phase on subsequent examinations.
    • If MRI is used then the same sequence (e.g. T1 or T2 weighted images) in the same anatomical plane should be used.
  • Add the longest diameters of the target lesions and report this as the baseline sum longest diameter. This will be used as a reference by which the tumour response will be measured.

LYMPH NODE MEASUREMENT RULES

  • Measure short axis
    • Target lesion if short axis  > 15mm
    • Non-target lesion is short axis 10 to < 15mm
    • Normal if short axis < 10mm
  • Add ACTUAL short axis measurements to sum of longest diameters of non-nodal lesions.
  • When considered normal if < 10mm, for CR the sum may not be zero if nodes are included as target lesions.
  • The implication of this is that patients previously considered PR because of residual nodes <10mm may now be considered CR.

RESPONSE DEFINITIONS:

  • Complete response (CR): disappearance of all lesions (i.e. all evidence of disease, not just the target lesions) determined by 2 observations not less than 4 weeks apart. All lymph nodes must be non-pathological in size (<10mm short axis).
  • Partial response (PR): > 30% decrease in the sum of longest diameters of target lesions compared to baseline, with response or stable disease observed in non-target lesions, and no new lesions.
  • Stable disease (SD): neither sufficient shrinkage to qualify for response or sufficient increase to qualify for progressive disease in target lesions, with response or stable disease observed in non-target lesions, and no new lesions.
  • Progressive disease (PD): > 20% increase in the sum of longest diameters of target lesions compared to smallest sum longest diameter recorded. In addition, the sum must also demonstrate an absolute increase of at least 5mm. Unequivocal progression of non-target lesions, or the appearance of new lesions is also considered progression. Unequivocal progression means the patient has overall status of progressive disease at that time point. Modest increases in the size of one or more non-target lesions is usually not sufficient.

REMINDERS:

  • New lesions must be unequivocal and not attributable to a different scanning technique or non-tumour (e.g. "new" bone lesions may be flare). When in doubt continue treatment and repeat evaluation.
  • If a scan shows a new lesion in anatomical region which was not included in the baseline scans, this is still PD.
  • Response is judged against baseline, but progression is judged against the smallest recorded score.

EXAMPLES:

Month 0 3 6 9 12
Measurement (mm) 100 90 50 55 > 60
Classification Baseline SD PR PR PD

TIME POINT RESPONSE: PATIENTS WITH TARGET (+/- NON-TARGET) DISEASE

Target Lesions Non-target lesions New Lesions Overall response
CR CR No CR
CR Non-CR/Non-PD No PR
CR Not evaluated No PR
PR Non-PD or not all evaluated No PR
SD Non-PD or not all evaluated No SD
Not all evaluated Non-PD No NE
PD Any Any PD
Any PD Any PD
Any Any Yes PD

REFERENCES:

  1. Eisenhauer EA, Therasse, P et al. New response evaluation criteria in solid tumours: Revised RECIST guideline (version 1.1). Eur J Cancer 2009, 45, 228-247.
  2. Gehan EA and Tefft MC. Will there be resistance to the RECIST (Response Evaluation Criteria in Solid Tumours)? J Natl Cancer Inst 2000, 92, 179-181.