Tandem autologous hematopoietic stem cell transplantation (HSCT) could extend progression-free survival (PFS) for some patients with newly diagnosed multiple myeloma, based on long-term data from the phase 3 STaMINA trial.
While the intent-to-treat analysis showed no difference in 6-year PFS rate between single versus tandem HSCT, the as-treated analysis showed that patients who received two transplants had a 6-year PFS rate that was approximately 10% higher than those who received just one transplant, reported lead author Parameswaran Hari, MD, of the Medical College of Wisconsin, Milwaukee, who presented the findings as part of the American Society of Clinical Oncology virtual scientific program.
The STaMINA trial, also known as, involved 758 patients who were randomized to receive one of three treatment regimens followed by 3 years of maintenance lenalidomide: tandem HSCT (auto/auto), single HSCT plus consolidation with lenalidomide/bortezomib/dexamethasone (auto/RVD), and single HSCT (auto/len).
“At the time, we intended the study to stop approximately 38 months from randomization, allowing for the time for transplant, and then 3 years of maintenance,” Dr. Hari said. However, as the results of lenalidomide maintenance inwere reported, they allowed for a follow-on protocol, which provided patients who are progression-free at the completion of the original STaMINA trial to go on to a second follow-on trial, which allowed lenalidomide maintenance on an indefinite basis, he added.
The present analysis looked at the long-term results of this follow-on trial, including the impact of discontinuing lenalidomide.
Aligning with the original study, the present intent-to-treat analysis showed no significant difference between treatment arms for 6-year PFS rate or overall survival. Respectively, PFS rates for auto/auto, auto/RVD, and auto/len were 43.9%, 39.7%, and 40.9% (P = .6).
But 32% of patients in the tandem group never underwent second HSCT, Dr. Hari noted, prompting the as-treated analysis. Although overall survival remained similar between groups, the 6-year PFS was significantly higher for patients who underwent tandem HSCT, at 49.4%, compared with 39.7% for auto/RVD and 38.6% for auto/len (P = .03).
Subgroup analysis showed the statistical benefit of tandem HSCT was driven by high-risk patients, who had a significantly better PFS after tandem transplant, compared with standard-risk patients, who showed no significant benefit.
Dr. Hari called the findings “provocative.”
“The tandem auto approach may still be relevant in high-risk multiple myeloma patients,” he said.
Dr. Hari and his colleagues also found that patients who stayed on maintenance lenalidomide after 38 months had a better 5-year PFS rate than those who discontinued maintenance therapy (79.5% vs. 61%; P = .0004). Subgroup analysis showed this benefit was statistically significant among patients with standard-risk disease (86.3% vs. 66%; P less than .001) but not among those in the high-risk subgroup (86.7% vs. 67.8%; P = .2).
However, Dr. Hari suggested that, based on the similarity of proportions between subgroups, the lack of significance in the high-risk subgroup was likely because of small sample size, suggesting the benefit of maintenance was actually shared across risk strata.
“Lenalidomide maintenance becomes a significant factor for preventing patients from progression,” Dr. Hari said, noting that the tandem transplant approach requires further study, and that he and his colleagues would soon publish minimal residual disease data.
He finished his presentation with a clear clinical recommendation. “Preplanned lenalidomide discontinuation at 3 years is not recommended based on inferior progression-free survival among those who stopped such therapy,” he said.
Invited discussant Joshua R. Richter, MD, of the Icahn School of Medicine at Mount Sinai, New York, said the findings encourage high-dose maintenance therapy, and for some, tandem HSCT.
“The STaMINA study presented today supports the notion that some patients with high-risk disease still may benefit and have further tumor burden reduction with the second transplant that leads to deeper remissions and hopefully abrogates diminished outcomes,” Dr. Richter said during a virtual presentation.
But improvements are needed to better identify such patients, Dr. Richter added. He highlighted a lack of standardization in risk modeling, with various factors currently employed, such as patient characteristics and genomic markers, among several others.
“Better definitions will allow us to cross compare and make true analyses about how to manage these patients,” Dr. Richter said. “Despite the improvements across the board that we’ve seen in myeloma patients, high-risk disease continues to represent a more complicated arena. And patients continue to suffer from worse outcomes, despite all of the other advances.”
The study was funded by the National Institutes of Health. The investigators disclosed additional relationships with Amgen, Celgene, Novartis, and others. Dr. Richter disclosed affiliations with Takeda, Sanofi, Janssen, and others.
SOURCE: Hari et al. ASCO 2020. Abstract 8506.