Because dexamethasone remains a key component of myeloma therapy, we wished to examine the impact of baseline and relapse expression levels of the glucocorticoid receptor gene NR3C1 on survival outcomes in the context of treatment with or without thalidomide.
We investigated the clinical impact of gene expression profiling (GEP)–derived expression levels of NR3C1 in 351 patients with GEP data available at baseline and in 130 with data available at relapse, among 668 subjects accrued to Total Therapy 2 (TT2).
Low NR3C1 expression levels had a negative impact on progression-free survival (PFS, HR=1.47; p=0.030) and overall survival (OS, HR=1.90; p=0.002) in the no-thalidomide arm. Conversely, there was a significant clinical benefit of thalidomide for patients with low receptor levels (OS, HR=0.54, p=0.015; PFS, HR=0.54, p=0.004), mediated most likely by thalidomide’s up-regulation of NR3C1. In the context of both baseline and relapse parameters, post-relapse survival (PRS) was adversely affected by low NR3C1 levels at relapse in a multivariate analysis (HR=2.61, p=0.012).
These findings justify the inclusion of NR3C1 expression data in the work-up of patients with myeloma as it can significantly influence the choice of therapy and, ultimately, OS. The identification of an interaction term between thalidomide and NR3C1 underscores the importance of pharmacogenomic studies in the systematic study of new drugs.