International prognostic index (IPI)--a critical comparison with five multiple myeloma staging systems in the group of 270 patients treated by conventional chemotherapy

Abstract

In the group of 270 patients with multiple myeloma (MM) treated during 1991-2004 by conventional chemotherapy, the prognostic value and practical utility of IPI (International Prognostic Index) was assessed and compared with five other actual staging systems. Prognostic significance was assessed using the curves of overall survival (OS) according to Kaplan-Meier and log rank test (p<0.05). Good practical utility and prognostic significance of Durie-Salmon (D-S) system was confirmed (p<0.001). Good overall prognostic significance was observed in simple staging systems based on the measurement of beta2-microglobulin and albumin serum levels according to Bataille (p<0.001), SWOG (South West Oncology Group, p<0.001) and IPI (p<0.001). Regardless of a short 5-year duration of the study, the scoring system according to San Miguel enclosing apart from other parameters also propidium iodide proliferation index (PC-PI) of myeloma plasmocytes seems to be promising with very different characteristics of curves of overall survival (p<0.001). Very good prognostic value and easy practical utility were examined in Olomouc staging system (OSS) based on the measurement of beta2-microglobulin and thymidinekinase serum levels (p<0.001). With regard to detection of patients of stage 1, i. e. "low risk", not requiring an immediate initiation of conventional chemotherapy ("wait and see" approach), the most suitable was the system according to D-S, SWOG and IPI (median OS 77, 76 and 77 months). To select a cohort of "high risk" patients, i.e. stage 3, with very unfavourable disease prognosis, the most advantageous was the system OSS and San Miguel (median OS was 5 and 6 months) and/or SWOG system selecting patients of stage 4, i.e. "worst prognosis", with median OS 8 months. It was found that IPI did not meet expectations for effective identification of "high risk" patients (median OS of stage 3 was 20 months) nor for the distinction of different prognosis of patients during initial 25 months of MM course at stage 2 vs. 3. The study indicates that under conditions of common clinical practice and conventional chemotherapy, the staging system according to D-S is still useful, while practical application of SWOG and IPI as simpler alternative to the assessment of clinical stage should be verified by further comparative studies. In harmony with the progress in cytogenetics and molecular biology as well as a prospective requirement of individual target therapy, a future suitable stratification system should be based on parameters of internal biological properties of myeloma tissue and microenvironment of bone marrow, allowing in addition a continuous evaluation of the disease course and the effect of therapy.