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DOI:10.2214/AJR.06.5076.1
AJR 2006; 187:W553
© American Roentgen Ray Society

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T. Thomas Zacharia and Sanjay Saini

Massachusetts General Hospital Present address: Elmhurst, NY 11373
Massachusetts General Hospital Boston, MA 02114



 
WEB—This is a Web exclusive article.

We thank Dr. Schwartz and colleagues for their interest in our article on the minimum number of hepatic metastatic lesions that must be measured to assess patient response to therapy [1]. We would like to address their concerns regarding the methodology used and conclusions derived.

Our patient population was highly selective because the objective of our study was to redefine the minimum number of target lesions to be measured per organ. Other sites of metastases such as lungs and lymph nodes should be evaluated to determine patient response. The RE-CIST group (Response Evaluation Criteria in Solid Tumors Group) [2] states that all measurable lesions up to a maximum of five lesions per organ and 10 lesions in total, representative of all involved organs, should be identified as target lesions and recorded and measured at baseline. We emphasized the fact that assessing therapeutic response on the basis of hepatic metastases alone would not be accurate in several patients with metastatic colon cancer.

Colon cancer metastases to the liver can be either well defined and homogeneous or ill defined and heterogeneous, or a combination of both patterns of lesions. By measuring the well-defined homogeneous lesions, we can reduce the variability in measurements and give a more accurate assessment of treatment response. We concluded that response evaluation with two large, well-defined lesion measurements gave 100% concordant results to response with five target-lesion measurements and that single-lesion measurements gave concordant disease response when compared with multiple-lesion measurements in 93.33% of evaluations [1].

Our study was designed based on the new guidelines validated by the RECIST Group [2]. In the current guidelines, the section on response criteria (3.2. Response Criteria, 3.2.1. Evaluation of target lesions) provides the definitions of the criteria used to determine objective tumor response for target lesions. The criteria have been adapted from the original WHO Handbook [3], taking into account the measurement of the longest diameter only for all target lesions. The formula provided by Schwartz and colleagues could be useful for calculating the increase in variability that results when a selective group of tumors, rather than all available tumors, is selected for measurement [4].

A recent investigation by Therasse et al. [5] reviews the literature (a total of 60 articles) that has been published on RECIST from 2000 up to November 2005. They conclude that there is no universal method available as of now for tumor measurement. The findings of their review, together with the results of ongoing studies, will probably result in the presentation of an updated version of RECIST later this year [5].


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  1. Zacharia TT, Saini S, Halpern EF, Sumner JE. CT of colon cancer metastases to the liver using modified RECIST criteria: determining the ideal number of target lesions to measure. AJR2006; 186:1067 -1070[Abstract/Free Full Text]
  2. Therasse P, Arbuck SG, Eisenhauer EA, et al. New guidelines to evaluate the response to treatment in solid tumors: European Organization for Research and Treatment of Cancer, National Cancer Institute of the United States, National Cancer Institute of Canada. J Natl Cancer Inst 2000; 92:205 -216[Abstract/Free Full Text]
  3. WHO handbook for reporting results of cancer treatment. Geneva, Switzerland: World Health Organization Offset Publication No. 48; 1979
  4. Mazumdar M, Smith A, Debroy PP, Schwartz LH. A theoretical approach to choosing the minimum number of multiple tumors required for assessing treatment response. J Clin Epidemiol2005; 58:150 -153[CrossRef][Medline]
  5. Therasse P, Eisenhauer EA, Verweij J. RECIST revisited: a review of validation studies on tumour assessment. Eur J Cancer2006; 42:1031 -1039[CrossRef][Medline]

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This Article
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