# Moderate‐Severe Thrombocytopenia Portends Poor Outcomes in Multiple Myeloma

## TL;DR

Low platelet counts at diagnosis and during treatment are linked to worse survival in multiple myeloma patients.

## Contribution

This study identifies moderate-severe thrombocytopenia as a prognostic marker in multiple myeloma.

## Key findings

- Moderate-severe thrombocytopenia at diagnosis is associated with inferior overall survival in MM patients.
- Persistent or new thrombocytopenia during treatment also correlates with worse survival outcomes.
- The negative prognosis from thrombocytopenia remains even after standard therapies and stem cell transplants.

## Abstract

Malignant plasma cells in multiple myeloma (MM) reprogram the bone marrow microenvironment to support tumor expansion. This myeloma cell–hematopoietic stem cell interaction leads to fewer hematopoietic stem cells in the bone marrow and altered differentiation of megakaryocytes, which can contribute to MM disease‐related thrombocytopenia. Given the development of novel therapies for MM and the need for biomarkers reflecting the bone marrow microenvironment, we evaluated peripheral blood platelet count at diagnosis and during treatment of MM.

We retrospectively evaluated 14,313 patients diagnosed with MM between 2000 and 2019 at Veterans Administration hospitals using platelet count obtained closest to diagnosis and up to 2.5 years thereafter. Patients were stratified into four categories:  moderate‐severe thrombocytopenia, mild thrombocytopenia, normal platelets, and thrombocytosis (< 100, 100–149, 150–349, and ≥ 350 per microliter, respectively).

Thrombocytopenia, present in 25% of patients at diagnosis, corresponded to inferior overall survival (OS). During follow‐up, persistent or new thrombocytopenia was also associated with inferior OS. Moreover, the negative prognostication afforded by baseline moderate–severe thrombocytopenia remained despite standard therapies (hazard ratio [HR] 1.83; 95% confidence interval [CI] 1.70–1.97) and stem cell transplant (HR 1.41; 95% CI 1.34–1.48).

Our findings support the use of platelet count in MM as an easily accessible prognostic marker.

The authors have confirmed clinical trial registration is not needed for this submission.