Best Overall Tumor Response for Solid Tumors

Recist

Today RECIST 1.1 despite some existing criticism, is the recognized standard approach for defining tumor response for solid tumors and therefore for defining the Progression Free Survival (PFS). RECIST is a validated and « simplified » version of WHO specifically to be used in adult and paediatric cancer clinical trials (not in malignant brain tumour or malignant lymphoma studies).

MEASURABLE LESION or TARGET LESION It can be measured in one diameter:

• Longest Diameter (LD) 20 mm at least with conventional techniques
• Longest Diameter (LD) 10 mm with spiral CT scan

RECIST recommends a maximum of 10 measurable lesions (biggest and most suitable for repeated measures), maximum 5 measurable lesions per organ.

NON MEASURABLE LESION or NON TARGET LESION All other lesions, for example:

• LD < 20 mm with conventional techniques
• LD < 10 mm with spiral CT scan
• Truly non-measurable lesions (e.g bone)

Often having at least one measurable lesion is an eligibility criteria to enter into the study. RECIST recommends to perform a tumor assessment at regular intervals (usually every 2 cycles).

An assessment time-point is considered valid for the overall response evaluation if:

• All baseline lesions are assessed at the time point
• All lesions are assessed with the method used at baseline

Definition of Best Overall Tumor Response

The Best Overall Response (BOR) is the best response recorded from the start of the study treatment until the disease progression/recurrence:

• Complete Response (CR) upon confirmation at least 4 wks of 1st CR
• Partial Response (PR) upon confirmation at least 4 wks of first PR
• Stable Disease (SD)
• Progressive Disease (PD)

A requirement for SD is that it should be met at least once no less than 6-8 weeks after the first dose of trial treatment/baseline assessment, otherwise the best response will be Not Evaluable (NE). The criteria for confirmation of the response is summarized in the following table: