Background: [18F] fluorodeoxyglucose-positron emission tomography is incorporated in response criteria currently used for lymphoma; however, the primary endpoint in earlier phase study is an overall response, which includes the partial response of 50% shrinkage in two dimensions. Therefore, the measurement of target lesions is still prerequisite to determine the destiny of new, promising agents. Since required is calculating the sum of the product of bidimensional diameters of maximal six target lesions, the International Workshop Criteria (IWC) used as response evaluation in lymphoma is more time-consuming than the Response Evaluation Criteria in Solid Tumors (RECIST). This study aimed to examine whether the RECIST could replace the IWC using data from a phase II/III study of R-CHOP-21 versus R-CHOP-14 for advanced-stage indolent B-cell lymphoma, JCOG0203.
Methods: To evaluate the degree of agreement between them, the Kappa coefficient (KC) was calculated. Excluding patients without target lesions for the RECIST following central pathological review, 269 patients were evaluable. We determined which criterion was more predictive for progression-free survival. The criterion showing the lower point estimate of the hazard ratio (HR) of a complete response (CR) vs. a non-CR was defined as more useful.
Results: The KC between them was 0.34 (95% confidence interval [CI] 0.26-0.42); namely, indicating poor agreement. The HR of the IWC (0.47: 95% CI 0.33-0.68, log-rank test p < 0.001) was lower than that of the RECIST (0.64: 95% CI 0.45-0.89, p = 0.0075).
Conclusion: We conclude that unidimensional measurements cannot be substituted for the bidimensional ones for indolent lymphoma.
Keywords: Follicular lymphoma; Indolent B-cell lymphoma; International Workshop Criteria; JCOG; RECIST.