Size determination and response assessment of liver metastases with computed tomography—Comparison of RECIST and volumetric algorithms
Introduction
Accurate and reliable information on the extent of a malignant tumor is important for monitoring systemic anticancer treatment. Imaging is used to evaluate the local extent and systemic spread of malignant disease before treatment is initiated and to follow up the response to treatment mostly based on morphologic assessment of change in tumor size.
Different approaches exist to quantify the tumor burden and estimate changes in lesion size during systemic treatment. First time in 1979 specific criteria, based on the sum of the products of the maximum bidimensional tumor diameter were published by the WHO in order to simplify and standardize the assessment of tumors response to treatment [1], [2]. The first version of the Response Evaluation Criteria in solid tumors (RECIST) is based on a retrospective analysis of more than 4000 oncologic patients included in studies conducted in Europe and the United States of America and was published by the EORTC (European Organization for Cancer Research and Treatment), the NCI (National Cancer Institute of the United States), and the National Cancer Institute of Canada Clinical Trials Group in 1999 [3]. A second revised edition, based on the same principles was published in 2009 as RECIST 1.1 [4], [5].
The superiority of RECIST or two- or three-dimensional volumetry for liver metastases at baseline and the therapy induced alterations of tumor size for response assessment at follow-up are debated [6], [7], [8], [9]. The widespread use of multidetector computed tomography (MDCT) in centers participating in multicentric trials would allow for the employment of more sophisticated three-dimensional assessment of tumor size using thin slice data sets and different image post-processing algorithms.
Therefore, the aim of our study was to investigate and compare the reproducibility and intermodality variability of different three-dimensional volumetric methods and uni-dimensional measurement according to the RECIST 1.1 guideline in determining the size of liver metastases from gastrointestinal malignancies and to investigate possible differences between these methods in classifying the response to anticancer treatment in follow-up examinations.
Section snippets
Patients
The retrospective study included 45 consecutive patients with confirmed (histology from at least one lesion per patient) metastatic lesions from malignomas of the gastrointestinal tract. The primary tumors were pancreatic adenocarcinomas (n = 22), and colorectal adenocarcinomas (n = 23). For their different appearance on MDCT imaging, mucinous adenocarcinomas were excluded. In total, 24 men and 21 women with a median age of 61 years (range, 34–71 years) were evaluated. The institutional review board
Lesion volumes
The lesion volumes ranged between 0.2 and 52.9 cm3 for threshold-based segmentation (mean volume, 7.8 cm3), between 0.4 and 49.6 cm3 for slice-segmentation (mean volume, 7.8 cm3) and between 0.3 and 50.2 cm3 for the seeded region growing method (mean volume, 7.7 cm3). Maximum metastasis diameters ranged between 10.4 and 65.0 mm (mean diameter, 26.4 mm). The volumes calculated from the diameters on the assumption of a spherical shape according to the RECIST guideline ranged between 0.6 and 143.8 cm3
Discussion
The role of tumor volumetry in the follow-up examination of patients undergoing systemic therapy is discussed controversially in the literature [6], [7], [8], [9], [10], [12], [14], [15], [16], [17], [18]. Some authors do not see any clinical advantage of three-dimensional tumor size determination over one- or two-dimensional measurement [8], [9], while others advocate tumor volume determination for evaluating the response to chemotherapy [6], [7], [15].
Hopper et al. investigated 139 patients
Conclusions
In conclusion, this study supports the use of volumetric measurement methods due to significant higher intraobserver reproducibility compared to RECIST. Whether RECIST or the volumetric methods are more sensitive for the detection of a disease progression depends on the applied thresholds. A critical issue remains whether the simple mathematical extrapolation of RECIST to volumetric criteria is feasible. Prospective studies with larger patient numbers are warranted to investigate the value of
Conflict of interest
We wish to confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome.
Acknowledgement
We are grateful for Prof. F. D. Knollmann, who gave the idea of this study.
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