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Unbiased estimation of tumor regression rates during chemoradiotherapy for esophageal carcinoma using CT and stereology.

SUMMARY. The purpose of the present study is to estimate tumor volumes of 10 patients with esophageal carcinoma on serial CT images that are obtained before and after chemoradiotherapy using a stereological method. In this study, tumor volume was measured using the Cavalieri method of modern design stereology with a combination of three separate stages. Firstly, detailed systematic series of axial CT images of 1-cm thickness were obtained throughout the whole tumor area of each subject and to magnify them all CT images were projected on a screen by overhead projector and then were marked by manually tracing the outline of areas with tumor on serial CT images that are projected onto the screen. Secondly these images were drawn on paper. Finally the images on paper were evaluated with a point-counting method. It was shown in a pilot study analyzed that 100 test points counted on about 6--8 serial slices through for esophagus wall, lumen and wall + lumen are sufficient to secure coefficient of error (CE) on the estimates of volumes as in this study. It was found that tumor volumes before and after radiotherapy for esophagus wall, lumen and wall + lumen was 10.34 cm(3), 1.15 cm(3) and 11.75 cm(3) before and 5.93 cm(3), 1.43 cm(3) and 7.65 cm(3) after radiotherapy, respectively. When only esophagus wall and lumen volumes or wall + lumen volumes before and after radiotherapy were statistically compared, the difference between either esophagus wall (P<0.01) and lumen (P<0.01) volumes or total volumes (P<.1) were significant. It is concluded that CT estimated tumor volumes may be helpful in both evaluating the clinical situation of patients and providing a simple index to assess the efficiency of therapy, prediction of tumor regression rate and minimizing the risk of chemoradiotherapy damage.