Adding tyrosine kinase inhibitors to the treatment of patients with Philadelphia chromosome–positive acute lymphoblastic leukemia (Ph+ALL) has significantly improved outcomes in recent years, but it’s still unclear which patients will also benefit from bone marrow transplants, and whether chemotherapy will gradually fade into the therapeutic background, a leukemia researcher contended.
said Anjali S. Advani, MD, of the Cleveland Clinic Taussig Cancer Institute.
Dr. Advani discussed her approach to treating both fit and frail patients with Ph+ALL during the virtual American Society of Hematology (ASH) Meeting on Hematologic Malignancies.
Increasing understanding of the importance of eliminating minimal residual disease (MRD) colors decisions about the best TKI to use in the first line.
“In terms of which TKI to use in the upfront setting, no randomized study has been done, but since MRD is associated with improved response, we often use this data to make a decision,” she said. “This, however, is complicated, because TKIs are combined with chemotherapy, there are many new TKIs, and finally, although we can start with one TKI, we can change to another TKI if we see that a patient is not responding appropriately.”
With the use of second-generation TKIs in combination with chemotherapy, rates of complete molecular remission (CMR) and major molecular remission (MMR) improved significantly over those seen with the first-in-class agent imatinib.
Notably, she said, the combination of ponatinib (Iclusig) with steroids as frontline therapy for elderly or frail patients with Ph+ALL was associated with a 60.5% CMR at week 24 in a phase 2 Italian trial (Blood 2017;130[Suppl. 1]:99).
Combining ponatinib with the hyper-CVAD regimen (cyclophosphamide, vincristine, doxorubicin, dexamethasone) improved the 3-month CMR rate to 74% and, the MMR rate to 15% (Lancet Haematol Dec. 2018 Dec 1;5[12]:e618-e627).
A 2016 propensity-score analysis comparing hyper-CVAD plus ponatinib with the hyper-CVAD plus dasatinib showed significantly better event-free survival (P = .035) and overall survival (P = .025) with the ponatinib-containing combination (Cancer 2016;122[23]:3650-6).
As with all potent regimens, however, the combination of hyper-CVAD and ponatinib is associated with relatively high percentages of grade 3 or greater nonhematologic toxicities, including transaminase and bilirubin elevation, pancreatitis, hypertension, venous thromboembolic events and arterial cardiovascular events.
Transplants in the TKI era
Prior to the advent of TKIs, there was strong evidence of the benefit of allogeneic stem cell transplant in patients with Ph+ALL in first remission (BMT 2003;31:623-32).
“The question is, now that we use TKIs, should we be transplanting patients still?” Dr. Advani said.
In the U.S. intergroup S0805 study looking at the combination of dasatinib and chemotherapy, there were distinct relapse-free and overall survival benefits for patients who underwent transplant. This trial did not evaluate MRD, however, ”so what we don’t know is for those patients achieving a complete molecular remission, would those patients do okay without transplant?” she said.
The current standard of care at Cleveland Clinic is to transplant eligible patients in first remission, ”but I think that’s likely to change as we get more data from these trials.”
In the COG AALL0031 trial of imatinib and chemotherapy in children with Ph+ALL, there was no significant benefit to stem cell transplant (Leukemia 2014 Jan 20;28:1467-71), Dr. Advani noted.
Other prognostic features associated with poor risk, such as 1KZF1 mutations with CDKN2A and/or PAX5 deletions, have been suggested as indicators for transplant, but “what’s less clear is what the impact of these abnormalities is now with the second- and third-generation TKIs, and also whether these various abnormalities correlate with molecular responses or achievement of complete molecular remission,” she said.