Hirokazu Watanabe

We evaluated interobserver reproducibility for the response evaluation criteria in solid tumors (RECIST) guidelines and the influence of minimum lesion size (MLS) on reproducibility. The 110 consecutive patients with non‐small cell lung cancer were treated with platinum‐based chemotherapy. Five observers measured target lesions according to both the World Health Organization (WHO) criteria and RECIST. The percentage changes for unidimensional measurements (UD; RECIST type) and bidimensional measurements (BD; WHO type) were calculated for each patient. Interobserver reproducibility among five observers, that is 10 pairs, was expressed as the Spearman's correlation coefficient for the percentage changes, the proportion of agreement and the kappa statistics for response categories. The same analysis was carried out using MLS. BD was more reproducible than UD (Spearman rank correlation coefficient, 0.84 vs 0.81; proportion of agreement, 84.4% vs 82.5%; kappa value, 0.69 vs 0.61). When MLS was applied to UD, eligible cases decreased by 6.4% and the number of target lesions by 44.6%, whereas interobserver reproducibility for UD improved (Spearman rank correlation coefficient, 0.81–0.84; proportion of agreement, 82.5–84.2%; kappa value, 0.61–0.65). The introduction of MLS to UD could also improve intercriteria reproducibility between WHO and RECIST. It is important to apply the MLS when using RECIST for the comparable interobserver reproducibility attained with WHO. (Cancer Sci 2006; 97: 214–218)

We investigated the validity and inter‐criteria reproducibility between RECIST (Response Evaluation Criteria in Solid Tumors) guidelines and WHO (World Health Organization) criteria, considering the decrease in patient numbers resulting from inclusion of the minimum lesion size criterion introduced in RECIST guidelines. RECIST guidelines are based on unidimensional measurement and exclusion of small lesions from measurement. The aims of the study were to examine: (1) the effect of the minimum lesion size criterion, (2) the validity of unidimensional and bidimensional measurements, i.e., their relationship with tumor volume, (3) the inter‐criteria reproducibility between current RECIST guidelines and previous WHO criteria. One hundred and twenty patients with non‐small cell lung cancer (NSCLC) in clinical trials were evaluated. By applying the minimum lesion size criterion, six cases became ineligible without any influence on precision of tumor volume measurement. In the validity study, actual tumor volume was regarded as the gold standard. Although the unidimensional measurement had a lower correlation with tumor volume value than the bidimensional measurement, both the unidimensional measurement and bidimensional measurement correlated sufficiently well with tumor volume changes and the assessed tumor volume response. In the inter‐criteria reproducibility study between RECIST guidelines and WHO criteria, the response rate assessed by RECIST guidelines (19.3%) was almost the same as that assessed by WHO criteria (20.0%). In conclusion, RECIST guidelines are adequate for evaluating tumor response to chemotherapy in terms of both validity in relation to tumor volume and inter‐criteria reproducibility with the WHO criteria.