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To the editor: We read with interest the recent report from Lee et al. regarding the value of pelvic examination and imaging modality for the evaluation of tumor size in cervical cancer.1 Using pathologic results as standard reference, the authors compared the accuracy of pelvic examination with that of imaging modalities (CT or MRI) for tumor size measurement. Because the correlation coefficient between pelvic examination and pathologic results was higher than that between imaging modalities and pathologic results, the authors concluded that pelvic examination is superior to imaging modalities for tumor size measurement. However, we have several concerns with respect to the study.
First, as shown in Figure 1(B), tumor was not detected by imaging modalities in 21 patients; even an 8 cm-sized tumor was not detected by imaging modalities. We presumed that the undetected tumors of those patients could partially account for poor correlation between imaging modalities and pathologic results. Considering that CT is inferior to MRI in tumor visualization,2 we think that most of 21 patients might undergo CT alone. Therefore, the causes of insensitive imaging modalities should be addressed. If the insensitivity were due to CT, the result of subgroup analysis that included only patients who underwent MRI has to be presented.
Second, in terms of inclusion criteria, only patients with a clinically visible tumor were included in this study. However, the size of tumor can be measured with inspection, palpation, and colposcopic examination (althoughnot specifically addressed). Examiner would be able to measure the tumor size by palpation; hence, it is inappropriate to exclude the patients with a clinically invisible tumor (for example, a tumor located in endocervical canal). The inappropriate exclusion of patients with a clinically invisible tumor accounted for the fact that there were no tumors that were undetected by pelvic examination. Considering that, as we mentioned previously, tumors were undetected by imaging modalities in 21 patients and they presumably accounted for poor correlation between imaging modalities and pathologic results, the inappropriate inclusion criteria could cause a selection bias. In addition, the inappropriate inclusion criteria made the result of this study difficult to apply to patients with an endocervical tumor.
Third, in the discussion section, the authors insisted that the accuracy of CT and MRI is overestimated by quoting the result of ACRIN 6651/GOG 183 Intergroup study.4 However, the authors did not mention another study which included the re-analysis of the result of ACRIN 6651/GOG 183 Intergroup study and directly addressed the same issue with the current study.4 In the study including 172 patients with cervical cancer, MRI is superior to CT and pelvic examination for measuring tumor size using pathologic results as the standard reference.4 The authors should have explained the discrepancies between the current study and ACRIN 6651/GOG 183 Intergroup study.
Finally, we recommend a measurement method of tumor size at the time of colposcopic examination. We use a commercially available 8mm-sized round white paper, which is easily attached on the cervix, and then take a picture after application of lugol solution. The actual size of lesion can be measured by comparing the sizes of the lesion and 8 mm-sized reference paper.