S52-60_KKU 9.pmd

Background: Post-treatment I-131 whole body scan (WBS) is known to be a very sensitive test in detecting metastasis in differentiated thyroid cancer (DTC). Therefore, in the presence of this sensitive method, the role of chest radiography (CXR) in the diagnosis of pulmonary metastasis has been questioned. Objective: The present study aimed to find the prevalence of pulmonary metastasis found on CXR in DTC patients who had negative post-treatment WBS. Material and Method: Retrospective comparison was undertaken of CXR and post-treatment WBS routinely performed in 300 DTC patients during the time of I-131 treatment from January 2003 to December 2006 in the Department of Radiology. Radiographic patterns of pulmonary metastasis classified as single nodule, multiple nodules, lymphangitic metastasis and pleural metastasis were also recorded. Results: Of the 300 DTC patients, 36 pulmonary metastases (12.0%) were diagnosed based on CXR and post-treatment I-131 WBS. Of these 36 cases, 11 (30.6%) were detected by both CXR and WBS, whereas 16 (44.4%) were detected by WBS alone and 9 (25.0%) by CXR alone. Seven of these 9 cases (77.8%) had lymphangitic pattern of pulmonary metastasis. Conclusion: Although routine CXR has a limited role in the diagnosis of pulmonary metastasis in DTC patients being treated with I-131, it is helpful in detecting pulmonary metastasis in patients with negative post-treatment WBS.