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Measuring response in solid tumors: unidimensional versus bidimensional measurement
K James1, E Eisenhauer, M Christian
1National Cancer Institute of Canada Clinical Trials Group, Queen's University, Kingston, ON. jamesk@ncic.ctg.queensu.ca
Background:
Tumor shrinkage is a common end point used in screening new cytotoxic agents. The standard World Health Organization criterion for partial response is a 50% or more decrease in the sum of the products of two measurements (the maximum diameter of a tumor and the largest diameter perpendicular to this maximum diameter) of individual tumors. However, theoretically, the simple sum of the maximum diameters of individual tumors is more linearly related to cell kill than is the sum of the bidimensional products. It has been hypothesized that the calculation of bidimensional products is unnecessary, and a 30% decrease in the sum of maximum diameters of individual tumors (assuming spherical shape and equivalence to a 50% reduction in the sum of the bidimensional products) was proposed as a new criterion. We have applied the standard response and the new response criteria to the same data to determine whether the same number of responses in the same patients would result.
Methods:
Data from 569 patients included in eight studies of a variety of cancers were reanalyzed. The two response criteria were separately applied, and the results were compared using the kappa statistic. The importance of confirmatory measurements and the frequency of nonspherical tumors were also examined. In addition, for a subset of 128 patients, a unidimensional criterion for disease progression (30% increase in the sum of maximum diameters) was applied and compared with the standard definition of a 25% increase in the sum of the bidimensional products.
Results:
Agreement between the unidimensional and bidimensional criteria was generally found to be good. The kappa statistic for concordance for overall response was 0.95.
Conclusion:
We conclude that one dimensional measurement of tumor maximum diameter may be sufficient to assess change in solid tumors.
Insights
A new unidimensional measurement for tumor shrinkage is proposed as a simpler alternative to the standard bidimensional method. This approach may be sufficient for assessing solid tumor changes in clinical trials.
Area of Science:
- Oncology
- Clinical Trial Design
- Biostatistics
Background:
- Tumor shrinkage is a key endpoint in evaluating new cytotoxic agents.
- The World Health Organization (WHO) uses a 50% decrease in the sum of bidimensional products for partial response.
- A simpler unidimensional criterion based on maximum tumor diameter has been proposed.
Purpose of the Study:
- To compare the standard WHO bidimensional criteria with a new unidimensional criterion for assessing tumor response.
- To determine if the unidimensional criterion yields similar patient response rates as the bidimensional method.
- To evaluate the utility of unidimensional measurements in assessing solid tumor changes.
Main Methods:
- Reanalyzed data from 569 cancer patients across eight studies.
- Applied both standard bidimensional and proposed unidimensional response criteria separately.
- Compared results using the kappa statistic and examined confirmatory measurements and tumor shapes.
- Assessed a unidimensional progression criterion against the standard bidimensional definition in 128 patients.
Main Results:
- Good agreement was observed between the unidimensional and bidimensional criteria for overall response.
- The kappa statistic for concordance was 0.95, indicating high agreement.
- The unidimensional criterion for disease progression also showed good concordance with the standard definition.
Conclusions:
- One-dimensional measurement of maximum tumor diameter may be sufficient for assessing changes in solid tumors.
- The proposed unidimensional criterion offers a potentially simpler and equally effective method for tumor response assessment.
- This simplification could streamline the evaluation of cytotoxic agents in clinical settings.