The three-drug combination of Darzalex (daratumumab), Velcade (bortezomib) and dexamethasone is shifting the landscape of treatment and should become the new standard regimen for patients with relapsed/refractory multiple myeloma, according to Antonio Palumbo.
Encouraging findings from the phase 3 CASTOR trial, which were presented at the 2016 ASCO Annual Meeting, demonstrated that when Darzalex was added to Velcade and dexamethasone, it led to a 61 percent reduction in the risk of progression or death.
The median progression-free survival (PFS) was 7.2 months in the two-drug arm and was not yet reached in the Darzalex arm. The overall response rates were 83 percent and 63 percent in the experimental and control arms, respectively.
“The conclusion of this study could be that we observed a major advantage in terms of outcome—we saw a 61 percent reduction in the risk of disease progression, a doubling of the remission duration for patients receiving this combination of therapy, and a very good safety profile without any cumulative toxicity over the control arm,” says Palumbo, the lead CASTOR investigator.
In an interview with CURE, Palumbo, chief of the Myeloma Unit, Department of Oncology, University of Torino, discusses the practice-changing findings for relapsed/refractory patients and what questions remain with the three-drug regimen.
Can you share the design and exciting findings of the CASTOR trial?
These are major findings coming from a randomized study comparing the three-drug combination of Darzalex plus Velcade and dexamethasone versus the two-drug combination of Velcade and dexamethasone, which is the current standard of care for the treatment of relapsed/refractory patients with multiple myeloma.
In this study, almost 500 patients were randomized to receive Darzalex, Velcade and dexamethasone or Velcade and dexamethasone alone. The primary endpoint of the study was PFS.
The major finding from this study was the reduction in the risk of disease progression of 61 percent; this is unprecedented in comparison to other studies in relapsed/refractory multiple myeloma. This translated into a doubled remission time for patients who received this three-drug combination.
We also observed a major increase in response rate, leading to a most profound cytoreduction. The rate of complete response was doubled from 10 percent to 20 percent, and the rate of very good partial response was almost doubled from nearly 30 percent to 60 percent. This has relevant consequences because, in patients who have achieved profound cytoreduction, it did not only double the remission duration—it almost tripled the remission duration.
What was the safety profile of the triplet regimen?
From a safety point of view, the combination was very well tolerated. The major message is that they were no cumulative toxicities with the addition of the monoclonal antibody. The toxicities that were observed in the control arm were mainly the same in the experimental arm. Monoclonal antibodies do not usually have toxicities that are observed with chemotherapy combinations.
The only increased toxicity was the infusion reaction from the infusion of the antibody. This was present in 45 percent of patients, was mainly grade 1/2, and, in 98 percent of those cases, that adverse event was confined to the first infusion.
What are the next steps following this study?
Certainly, we need a longer follow-up. We still need to see if overall survival (OS) will give a major signal. At present, the follow-up is very short — only seven months — so we do not have any data on OS. Although the hazard ratio is already 0.7, it is, of course, not significant.
Are there any patients who are unfit to receive the triplet?
It is very well tolerated in all subgroups, including patients who are younger and older, have good or bad prognosis, and are in early-stage or late phases of disease. We do not have a specific exclusion for a subset of patients right now. The message here is to use it as early as possible because in early phases of disease, the efficacy is much higher.
How will these findings impact the treatment landscape of myeloma?
We have a new treatment paradigm. We will certainly include monoclonal antibodies in every single combination. R-CHOP has been the major standard of lymphoma, and, probably now, we are starting to see that Darzalex is the equivalent standard in including monoclonal antibodies for multiple myeloma.
What other remaining questions with this regimen should be answered?
The next question is to move to early phases of diseases because, now, the study has been performed in relapsed/refractory patients. We need to move quickly in the newly diagnosed patient, because, if we can copy what has been done here, the median remission of one to two years can be doubled to two to four years at diagnosis. A remission of four to five years could be doubled to eight to 10 years, and that is the major expectation for the future.
Looking ahead, what does the future hold for this field?
In the last 10 years, myeloma has had major improvements in survival. In the next couple of years, I do expect a further improvement in OS and probably will include the use of those agents in newly diagnosed patients—providing the opportunity to achieve a cure in a significant proportion of patients.