Bone marrow Ki-67 index is of prognostic value in newly diagnosed multiple myeloma

Abstract

Background: Ki-67 is an index of proliferative activity and is an established predictive and prognostic marker in multiple malignancies. However, its prognostic relevance in multiple myeloma (MM) is unclear. We investigated the relationship between Ki-67 expression and survival outcomes in MM in the era of novel therapies. Methods: We interrogated our database to identify patients with MM, newly diagnosed between July 1, 2013 and December 31, 2020, with Ki-67 expression assessed by immunohistochemistry (IHC) on bone marrow biopsies. Using an established threshold of 5% we defined Ki-67low (≤5%) and Ki-67high (>5%) subgroups for association with progression-free survival (PFS) and overall survival (OS). Results: Of 167 patients included: 53 (31.7%) had Ki-67high and 114 had Ki-67low. More patients with R-ISS 3 had Ki-67high (22.2% vs. 9.7%). The gain of 1q21 was overrepresented in the Ki-67high group (28% vs. 8%). Median PFS in the Ki-67low group was 3.1 years, and in the Ki-67high group 1.6 years (log-rank p 5%) is an independent prognostic marker associated with worse OS and PFS in newly diagnosed MM. IHC staining for Ki-67 on bone marrow biopsies could be easily adopted as a prognostic biomarker for MM in economically constrained healthcare settings.