RECIST 1.1: comparison with RECIST 1.0

The differences between RECIST 1.1 and RECIST 1.0 are as follows

RECIST 1.0

• measurable disease at baseline: required
• minimum target lesion size :
  • ≥ 10≥10 mm (spiral CT)
  • ≥ 20≥20 mm (conventional CT, MRI)
• measurement: longest dimension (LD)
• PD (progressive disease): 20% increased in LD from Nadir
• non measurable assessment: unequivocal progression
• lymph node measurements: none
• PET: not available

RECIST 1.1

• measurable disease at baseline: not always mandatory
• minimum target lesion size :
  • ≥ 10≥10 mm (CT + MRI) - or 2 x slice thickness
  • ≥ 15≥15 mm for lymph nodes
  • ≥ 20≥20 mm on chest x-ray
• measurement: longest dimension but for lymph nodes = short axis dimension
• PD: same as 1.0, but the increase should also be at least 5mm5 mm from Nadir
• non measurable assessment : substantial worsening / tumour/tumour burden has increased sufficiently
• lymph node measurements: specific instructions ≥ 15mm≥15mm, 10 - 14mm-14 mm, < 10mm10;10 mm>
• PET: may be considered to support CT, for PD and confirmation of CR

Discussion

Looking back at RECIST 1.0, several changes in RECIST 1.1 stand out. The most important modifications are that the total number of target lesions has been halved, cystic tumors and osteolytic metastases with soft tissue components are now measureable (provided the soft-tissue component is measureable), short axis measurements are taken in case of lymph nodes, PD based on non-target lesions is clearly defined, and a minimum 5mm absolute increase is needed in addition to a 20% increase for PD². Other features worth separate mention are:

Regarding imaging modalities, now a frontal chest radiograph may be used just like CT to measure and compare disease burden.

Lesions which break down into several smaller ones or coalesce into a single one are still measured, except that in the former case, longest dimensions of individual entities are measured and may thus differ in orientation.

Fate of target lesions which become too small but yet visible on follow-up: they should be assigned a default value of 5mm ²

Malignant mesothelioma is a circumferential tumor and not easily given to measurement of long axis diameter. A proposed method to consistently measure these lesions is to take maximum tumor depth at anatomically reproducible landmarks ²  

CR in lymph nodes:: this is defined as nodal short axis diameter of <10 mm on follow-up ( as opposed to disappearance in target lesions).

Lesion in an area not covered at baseline: this is considered to be PD according to RECIST 1.1. for details please refer to reference (2).

Equivocal new lesions: aa clear-cut new lesion, i.e., one not attributable to technical difference between examinations or pathology besides metastases, is evidence of PD. however, equivocal new lesions should be subjected to follow-up before assigning them to a category

Ultrasound remains unqualified for the purposes of RECIST.

See also

• RECIST