Dexamethasone dose intensity does not impact outcomes in newly diagnosed multiple myeloma: a secondary SWOG analysis

• Dexamethasone dose reductions below 40-60 milligrams weekly are common in multiple myeloma, even for patients enrolled on clinical trials.

• Dexamethasone dose reductions did not impact PFS or OS in newly diagnosed multiple myeloma in multivariate analyses.

Dexamethasone is a key component of induction for newly diagnosed multiple myeloma (NDMM) despite common toxicities including hyperglycemia and insomnia. In the randomized ECOG E4A03 trial, dexamethasone 40 milligrams (mg) once weekly was associated with lower mortality than higher doses of dexamethasone. However, the performance of dexamethasone dose reductions below this threshold with regard to progression-free survival (PFS) and overall survival (OS) in NDMM have not been fully characterized. We conducted a secondary pooled analysis of the S0777 and S1211 SWOG studies of NDMM, which employed lenalidomide-dexamethasone (Rd) alone with or without bortezomib (VRd) and with or without elotuzumab (Elo-VRd). Planned dexamethasone intensity was 40-60 mg weekly in all arms. Patients were categorized into FD-DEX (full-dose dexamethasone maintained throughout induction) or LD-DEX (lowered-dose dexamethasone or discontinuation; only permitted for Grade 3+ toxicities per both study protocols). Of 541 evaluated patients, the LD-DEX group comprised 373 patients (69%). There was no difference in PFS or OS between the FD-DEX or LD-DEX groups, which were balanced in terms of age, stage, and performance status. Predictors of PFS and OS in multivariate models were treatment arm, age ≥70, and thrombocytopenia; FD-DEX did not significantly improve either outcome. Our study suggests that dexamethasone dose reductions are common in multiple myeloma, even within clinical trials. Given dexamethasone's many toxicities and unclear benefit in the era of modern treatment regimens, dexamethasone dose reduction during NDMM induction warrants further prospective study. NCT00644228, NCT01668719