Measurement of response of pulmonal tumors in 64-slice MDCT

Advances in CT technology from single to multi-detector row CT (MDCT) permit a high resolution and volumetric presentation of pulmonary lesions. This implicates emerging measurement techniques that need to be contrasted with established methods.

To compare bidimensional, unidimensional, and volumetric methods for evaluation of treatment response in patients with lung lesions.

This study comprised 68 patients with pulmonary lesions who underwent a total of 276 64-MDCTs of chest at baseline and follow-up. RECIST and WHO criteria were used for unidimensional and bidimensional methods and region growing (RG) for volumetry. Patients were classified into four response categories. Respectively, two measurement techniques were contrasted and the kappa index was calculated. For intra-observer reproducibility the relative measurement error (RME) and kappa index with regard to agreement of response categories were evaluated.

Comparison of WHO und RECIST criteria achieves high correlation with kappa indices of 0.76 and 0.82. In particular, lesions with moderate increase of size in the range of 25-44% for bidimensional and 12-29% for unidimensional measurement result in different response categories when applying WHO and RECIST criteria. WHO criteria delivered PD more often than RECIST. kappa indices of 0.79 and 0.87 were attained in comparison of RECIST and RG, and 0.83 and 0.84 for WHO and RG. RME was 2.82% for RECIST, 7.53% for WHO, and 8.97% for RG. Intra-observer reproducibility was 95% for RECIST, 95% for WHO, and 96% for RG.

The comparison of all methods resulted in no statistically significant differences. WHO criteria seemed to diverge the most, they declared several lesions prematurely as progression, and showed no benefit in comparison to RECIST. RG showed the best reproducibility, considered irregular lesions, was slightly superior to RECIST, and could be applied uniformly. Unidimensional measurement represents an adequate alternative with the advantage of better clinical work flow.