Ki-67 expression level, histological subtype, and the International Prognostic Index as outcome predictors in mantle cell lymphoma

Objectives: Mantle cell lymphoma (MCL) is characterised by translocation t(11;14) (q13;q32) leading to rearrangement of bcl1/CCND1 and overexpression of the cell-cycle regulatory protein cyclin D1. We assessed the significance of the cell proliferation rate as an outcome predictor with the five components of the International Prognostic Index (IPI) and the histological subtypes of MCL. Patients and methods: The hospital case records and histopathological material of 127 patients diagnosed with MCL in a single centre were reviewed. The cell proliferation rate was assessed by Ki-67 immunostaining and mitosis counting. Cox's multivariate regression model was used in multivariate survival analyses. The median follow-up time was 87 months. Results: The mantle zone/nodular subtype of the common variant (19%) was associated with median survival of 70 months, the diffuse subtype of the common variant (64%) of 35 months, and the blastoid subtype (17%) of 11 months (P< 0.001). Patients with Ki-67 expression in greater than or equal to 26% (the upper tertile) of the lymphoma cells had median survival of only 13 months as compared with 45 months in the rest of the patients (P<0.001). In a multivariate analysis high Ki-67 expression, Ann Arbor stage III-IV, and age over 60 yr had independent influence on survival, whereas serum lactate dehydrogenase level, the number of extranodal disease sites, and performance status did not. Conclusions: The IPI may not be an optimal tool for outcome prediction in MCL, and a better prognostic index may be obtained by including Ki-67 expression and possibly the histological subtype in the index.