Value of functional imaging in precise radiotherapy for esophageal carcinoma

Abstract

Objective To investigate the value of PET-CT in TNM staging and three-conformal radiotherapy (3DCRT) in esophageal carcinoma. Methods From September 2007 to November 2008, 20 patients with pathologically confirmed esophageal carcinoma were enrolled, including 2 treated with surgery and 18 with 3DCRT. All the patients received PET-CT simulation before the treatment. The length and maximum transverse diameter of Grit based on esophagoscope, esophagography, CT, PET-CT_(SUV2.5) and PET-CT_(40%SUVmax) were compared. The TNM stages were compared based on CT and PET-CT images. Three treatment plans were produced and analyzed based on images of CT, PET-CT_(SUV2.5) and PET-CT_(40%SUVmax),respectively. Results The length of lesion on esophagoscope, esophagography, CT, PET-CT_(SUV2.5) and PET-CT_(40%SUVmax) was 4. 93 cm, 5.06 cm, 6. 67 cm, 5. 89 cm and 4. 84 cm, respectively. The corresponding maximum transverse diameter on the last 3 images was 4. 05 cm, 3.38 cm and 2. 95 cm, respectively. In all, 31, 21 and 14 positive lymph nodes were identified according to CT images, PET-CT images and the both. Five patients with CT diagnosed stage M_0 were found to have distant metastasis by PET-CT images, and 1 patient with CT diagnosed stage M_1 was excluded by PET-CT. The volumes of GTV_(CT) were similar with GTV_(SUV2.5) in 2 patients, smaller in 5 patients, and larger for the remaining 13 patients. For these 13 patients, the radiation dose of normal tissues based on GTV_(SUV2.5) was relatively lower. Conclusions The length of lesion based on PET -CT_(SUV2.5) matches the pathological length best , followed by esophagography. With PET-CT_(40%SUVmax) the actual lesion length may be underestimated. TNM stage might be changed by PET-CT, and then the target volumes and radiation doses of normal tissues might be reduced. Key words: Tomography,positron emission; Tomography, X-ray computed; Image fusion; Esophageal neoplasm; Staging