A CLINICAL-EVALUATION OF THE INTERNATIONAL LYMPHOMA STUDY-GROUP CLASSIFICATION OF NON-HODGKINS-LYMPHOMA

The recognition of several new types of non-Hodgkin's lymphoma (NHL) i n recent years has led to proposals for changing lymphoma classificati ons, including a new proposal put forth by the International Lymphoma Study Group (ILSG). However, the clinical significance of the new enti ties and the practical utility of this new proposal have not been stud ied. Therefore, we performed a clinical evaluation of the ILSG classif ication, A cohort of 1,403 cases of NHL was organized at nine study si tes around the world and consisted of consecutive patients seen betwee n 1988 and 1990 who were previously untreated. A detailed protocol for histologic and clinical analysis was followed at each site, and immun ologic characterization as to T- or B-cell phenotype was required, Fiv e expert hematopathologists visited the sites and each classified each case using the ILSG classification. A consensus diagnosis was also re ached in each case, and each expert rereviewed a 20% random sample of the cases. Clinical correlations and survival analyses were then perfo rmed. A diagnosis of NHL was confirmed in 1,378 (98.2%) of the cases. The most common lymphoma types were diffuse large B-cell lymphoma (31% ) and follicular lymphoma (22%), whereas the new entities comprised 21 % of the cases. Diagnostic accuracy was at least 85% for most of the m ajor lymphoma types, and reproducibility of the diagnosis was 85%. Imm unophenotyping improved the diagnostic accuracy by 10% to 45% for a nu mber of the major types, The clinical features of the new entities wer e distinctive. Both the histologic types and the patient characteristi cs as defined by the International Prognostic Index predicted for pati ent survival. In conclusion we found that the ILSG classification can be readily applied and identifies clinically distinctive types of NHL. However, for clinical application, prognostic factors as defined by t he International Prognostic Index must be combined with the histologic diagnosis for appropriate clinical decisions. (C) 1997 by The America n Society of Hematology.