Suitability of semi-automated tumor response assessment of liver metastases using a dedicated software package

To evaluate the suitability of semi-automated compared to manual tumor response assessment (TRA) of liver metastases.

In total, 32 patients with colorectal cancer and liver metastases were followed by an average of 2.8 contrast-enhanced CT scans. Two observers (O 1, O 2) measured the longest diameter (LD) of 269 liver metastases manually and semi-automatically using software installed as thin-client on a PACS workstation (LMS-Liver, MEDIAN Technologies). LD and TRA ("progressive", "stable", "partial remission") were performed according to RECIST (Response Evaluation Criteria in Solid Tumors) and analyzed for between-method, interobserver and intraobserver variability. The time needed for evaluation was compared for both methods.

All measurements correlated excellently (r>or=0.96). Intraobserver (semi-automated), interobserver (manual) and between-method differences (by O 1) in LD of 1.4+/-2.6 mm, 1.9+/-1.9 mm and 2.1+/-2.0 mm, respectively, were not significant. Interobserver (semi-automated) and between-method (by O 2) differences in LD of 3.0+/-3.0 mm and 2.6+/-2.0 mm, respectively, reflected a significant variability (p<0.01). The interobserver agreement in manual and semi-automated TRA was 91.4 %. The intraobserver agreement in semi-automated TRA was 84.5%. Between both methods a TRA agreement of 86.2% was obtained. Semi-automated evaluation (2.7 min) took slightly more time than manual evaluation (2.3 min).

Semi-automated and manual evaluation of liver metastases yield comparable results in response assessments and require comparable effort.