COMPARISON OF RESPONSE EVALUATION IN SMALL-CELL LUNG-CANCER USING COMPUTERIZED-TOMOGRAPHY AND CHEST RADIOGRAPHY

The percentage of patients achieving a complete response (CR) to thera py is often used as a measure of treatment efficacy in SCLC. Chest rad iographs are difficult to evaluate following therapy and differences i n reported response rates may be due to interobserver variation. CT sc ans of the thorax are more costly and are not as easily obtained as ro utine studies. We wanted to determine whether the measurability rate a nd interobserver agreement on response was superior when using CT scan s, compared to 'chest radiographs alone. Fourteen radiologists with ex pertise in CT imaging of the thorax, reviewed 15 cases of SCLC pre- an d post-chemotherapy (21 0 observations). In the first session, reviewe rs were required to measure or evaluate all possible lesions on the pl ain chest radiograph done at pre- and post-treatment. In the second se ssion, accompanying CT scans were provided in order to make the same a ssessments. The number of instances in which neoplastic disease was me asurable in two cross-sectional diameters on pretreatment films was 16 4 (79%) on chest radiographs and 202 (97%) on CT scans. Interobserver agreement was assessed by comparing tumour measurements, as well as re ports of complete disappearance of tumour (CR) among the 15 observers. The rate of CR ranged from 0 to 87% with the use of the chest radiogr aph, and from 0 to 95% using the CT scan. Usually after viewing the CT scan, readers changed their opinion as to whether CR had actually occ urred. For example, in one case, 87%, of readers judged response to th erapy as a CR based on chest radiograph; upon reevaluation with a CT s can this figure decreased to 15%. Agreement as to response was better on review of the CT scans, compared to the chest radiograph in all but two cases. It is therefore recommended that pre- and post-treatment C T scans, and not just chest radiographs, be used for assessment of res ponse to therapy.