Common Terms in Clinical Trial Reports

Since we frequently encounter clinical trial reports, mastering a few key terms can make it much easier to interpret their contents. Here we share some of the most common terms found in trial reports, hoping to benefit those interested in reading the literature.

For assessing short-term treatment response, changes in tumor size are observed and categorized using the following terms:

1. Complete Response (CR) Upon examination, all measurable lesions have completely disappeared, with no new lesions appearing, sustained for four weeks or more.

2. Partial Response (PR) Measured or assessed lesions have shrunk by more than 50%, with no progression and no new lesions, sustained for four weeks or more.

3. No Change (NC) / Stable Disease (SD) Measured or assessed lesions have shrunk by less than 50%, with no progression and no new lesions, sustained for four weeks or more.

4. Progressive Disease (PD) Measured or assessed lesions have increased by more than 25%, or new lesions have appeared, or disease is continuously worsening.

Whether a treatment is effective — that is, whether no cancer cells are found in the body — may be described as a complete response. Generally, if there is no sign of recurrence after several years of follow-up, the period is referred to as the disease-free interval, which may also be considered a cure. A reduction in tumor size by more than half is called partial response. If the tumor neither grows nor shrinks, it is called stable disease. Unfortunately, if the tumor continues to grow and worsen, this is called progressive disease.

For long-term efficacy, annual survival rates are typically used. For some late-stage patients, quality of life measures may also be used, such as pain relief status and functional status.

In clinical settings, there is also an assessment tool called RECIST (Response Evaluation Criteria in Solid Tumors). The definitions of CR, PR, SD, and PD differ slightly here. CR under RECIST applies to the total tumor size — confirmation of complete disappearance for four weeks is required, with up to five lesions per organ and no more than ten total lesion sites. PR requires at least a 30% reduction in the sum of the longest diameters of target lesions. SD is simply neither CR nor PR. PD is defined as a 20% or more increase in the sum of the longest diameters, or the appearance of new lesions.

This article was written with reference to an article by Dr. Minglin He of Changhua Christian Hospital (Lung Cancer and Patient Education Network).

We hope this helps you when reading clinical trial reports. If you have any questions, please feel free to contact us.

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