Validation of International Staging System (ISS) for Multiple Myeloma: A Retrospective Analysis of 487 Patients at 8 Brazilian Centers.

Introduction: The survival of patients with multiple myeloma varies from a few months to more than 10 years. This heterogeneity is related to the characteristics of the myeloma itself and of the host. The identification of the factors which influence the prognosis is very important to predict the result, assist in the choice of the treatment and adequately stratify the patients in clinical studies. Many prognostic factors have been identified in patients with multiple myeloma, such as anemia, renal failure, ß₂ microglobulin, albumin and chromossomic alterations. Some authors have combined prognostic factors and proposed various systems of staging. However, none of them have yet substituted the Durie-Salmon staging system. Recently, the International Myeloma Working Group, with the objective of developing a simple and reliable staging system, which can be internationally applied to classify and stratify patients with multiple myeloma, identified 3 risk groups. This new system of staging, the “International Staging System” (ISS), consists of stage I: ß₂ microglobulin < 3.5 mg/L plus albumin ≥ 3.5 g/dL (median survival: 62 months); stage II: neither I nor III (median 44 months); stage III: ß₂ microglobulin > 5.5 mg/L (median 29 months). This study included sites in North America, Europe and Asia, but the sites in Latin America were not included.

Objective: To validate the ISS in patients with multiple myeloma at Brazilian centers.

Patients and Methods: Four hundred and eighty-seven patients with the diagnosis of multiple myeloma within the period of 1998 to 2004 at Santa Casa de São Paulo, Hospital Universitário Clementino Fraga Filho do Rio de Janeiro, Hospital das Clínicas de São Paulo, Hospital São Paulo, Hospital das Clínicas de Ribeirão Preto, HEMOPE, Hospital Prof. Edgar Santos de Salvador and Hospital de Clínicas de Porto Alegre, with available data on albumin and ß₂ microglobulin, were stratified according to the ISS. A total of 339 patients received standard therapy and 148 received high-dose therapy as initial therapy. The survival was estimated using the Kaplan-Meier method with differences in survival examined using the logrank test.

Results: The median age of the patients was 60 years, 52% male and 48% female. In Stage I (n=104), the global median survival was not reached, the survival at 60 months was 60%, in stage II (n=264), the global median survival was 61 months and in stage III (n=119), 19 months (p<0.001).

Conclusion: The new system of staging for multiple myeloma (ISS) is simple, based on variables easy to be applied and was possible to be validated in patients with multiple myeloma in Brazilian centers.