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Table 2. Definitions of Tumor Response Terminology Relevant to GISTa

Term

Definition

Complete response (CR)

The disappearance of all signs of cancer in response to treatment. This does not always mean the cancer has been cured.

Partial response (PR)

A decrease in the size of a tumor, or in the extent of cancer in the body, in response to treatment.

Response rate (RR)

The percentage of patients whose cancer shrinks or disappears after treatment. RR = CR + PR

Stable disease (SD)

Cancer that is neither decreasing nor increasing in extent or severity.

Progressive disease (PD)

Cancer that is growing, spreading, or getting worse.

RECIST criteria

RECIST criteria are a voluntary, international standard for measuring tumor response based on measurable disease (i.e., the presence of at least one measurable lesion). RECIST criteria offer a simplified, conservative, extraction of imaging data and presume that linear measures are an adequate substitute for 2-D methods. There are four response categories:

  1. CR = disappearance of all target lesions.
  2. PR = 30% decrease in the sum of the longest diameter of target lesions.
  3. PD = 20% increase in the sum of the longest diameter of target lesions.
  4. SD = small changes that do not meet above criteria.

SWOG criteriab

SWOG criteria are based entirely on CT or MRI:

  • CR = disappearance of all disease that could be measured and evaluated.
  • PR = ≥ 50 percent decrease in the sum of the products of the perpendicular diameters of all measurable lesions, the absence of progression, and the absence of new lesions.
  • PD = ≥ 50 percent increase or an increase of 10 cm2 (whichever was smaller) in the sum of the products of the perpendicular diameters of all measurable lesions, worsening of a lesion that could be evaluated, the reappearance of and lesion or the presence of a new lesion.
  • SD = a response that did not qualify as a complete response, a partial response or disease progression.

Overall survival

The percentage of subjects in a study who have survived for a defined period of time. Usually reported as time since diagnosis or treatment. Also called the survival rate.

Time to progression

A measure of time after a disease is diagnosed (or treated) until the disease starts to get worse.

Progression-free survival

One type of measurement that can be used in a clinical study or trial to help determine whether a new treatment is effective. It refers to the probability that a patient will remain alive, without the disease getting worse.

Disease-free survival

Length of time after treatment during which no cancer is found. Can be reported for an individual patient or for a study population.

Event-free survivalc

Length of time after treatment that a participant in a clinical study remains free of pre-defined events. Events are defined by the study and can include adverse treatment effects, tumor recurrence/progression, or survival.

Survival rate

The percentage of people in a study or treatment group who are alive for a given period of time after diagnosis. This is commonly expressed as 5-year survival.

Notes:
a. Except as noted, these definitions were quoted from the NCI's www.cancer.gov Web site.
b. Defintion from 44.
c. Definition derived from http://www.intelihealth.com/IH/ihtPrint/WSIHW000/8096/8241/347567.html?d=dmtContent&hide=t&k=basePrint#efsurvival.

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