# Prognostic Significance of SGK1 Expression in Multiple Myeloma Patients Undergoing Autologous Hematopoietic Stem Cell Transplantation: A Single‐Center Retrospective Study

## TL;DR

This study shows that SGK1 gene expression in blood cells can predict relapse in multiple myeloma patients after stem cell transplants.

## Contribution

SGK1 gene expression is proposed as a new biomarker for predicting relapse in multiple myeloma after AHSCT.

## Key findings

- SGK1 expression levels decreased with reduced disease burden after AHSCT.
- SGK1's predictive power (AUC of 0.86) is comparable to traditional MRD assessments (AUC of 0.88).
- High SGK1 expression in high-risk patients is strongly linked to increased relapse risk.

## Abstract

This research attempts to assess the prognostic significance of serum/glucocorticoid‐regulated kinase 1 (SGK1) expression in peripheral blood mononuclear cells (PBMCs) of multiple myeloma (MM) individuals undergoing autologous hematopoietic stem cell transplantation (AHSCT) compared to traditional minimal residual disease (MRD) and serum free light chain (sFLC) assessments.

A single‐center, retrospective study was carried out involving 85 MM individuals who underwent AHSCT. SGK1 gene expression was measured in PBMCs using quantitative real‐time PCR (qRT‐PCR) at baseline and at defined post‐transplant intervals. Concurrently, MRD status was assessed using multiparameter flow cytometry (MFC) and sFLC levels were measured. Individuals were seen for a median of 36 months post‐transplant. ROC curve analysis was employed to assess the predictive power of SGK1 expression, MRD, and sFLC for relapse.

SGK1 gene expression demonstrated dynamic changes in AHSCT, with levels decreasing in all risk groups, reflecting reductions in disease burden. Quantitative analysis showed that the predictive efficacy of SGK1, utilizing the area under the receiver operating characteristic (ROC) curve (area under the curve [AUC]), was highly comparable to that of MRD assessments, with SGK1 achieving an AUC of 0.86, closely approximating the MRD AUC of 0.88. Persistent high SGK1 expression, particularly discernible in individuals harboring high‐risk (HR) cytogenetic profiles, was considerably associated with an elevated risk of relapse (hazard ratio for high vs. low SGK1 expression: 2.7; 95% CI: 1.4–5.3; p  < 0.01).

SGK1 gene expression in PBMCs serves as a promising, minimally invasive biomarker for relapse prediction in MM individuals undergoing AHSCT.