© Todd Buchanan 2016
SAN DIEGO—Updated results of the EURO-SKI trial support the idea that certain chronic myeloid leukemia (CML) patients can safely stop tyrosine kinase inhibitor (TKI) therapy.
About half of the patients studied, who had been in deep molecular remission for at least 1 year, had no evidence of relapse for at least 1 year after stopping TKI therapy.
Francis-Xavier Mahon, MD, PhD, of the Bergonie Cancer Center at the University of Bordeaux in France, presented this finding at the 2016 ASH Annual Meeting (abstract 787*).
Stopping treatment is an emerging goal of CML management. Several studies have demonstrated the feasibility of stopping treatment, and consistent results over time have validated the concept of treatment-free remission (TFR), Dr Mahon said.
“A sustained deep molecular response on long-term TKI therapy seems to be necessary prior to attempting TFR,” he noted. “However, the exact preconditions for stopping CML treatments are not yet defined.”
Dr Mahon and his colleagues studied 821 chronic phase CML patients treated with TKIs (imatinib, dasatinib, or nilotinib) for at least 3 years. The patients were in deep molecular remission (MR4) for at least a year.
Dr Mahon reported on an intention-to-stop-treatment analysis of 755 patients. Their median age at diagnosis was 52 years, median time from diagnosis to stopping TKI therapy was 7.7 years, median duration of TKI therapy was 7.4 years, and median duration of deep molecular remission before stopping TKI therapy was 4.7 years.
At a median follow-up of 14.9 months, about half of patients (378/755) were still alive and in major molecular response. Molecular recurrence-free survival was 61% at 6 months, 55% at 12 months, 52% at 18 months, 50% at 24 months, and 47% at 36 months.
Most loss of molecular response came within the first 6 months after stopping treatment. Most patients regained their previous remission level after resuming TKI therapy, and no study participants progressed to a dangerous state of advanced disease.
Dr Mahon noted that longer duration of imatinib therapy prior to stopping TKIs, optimally 5.8 years or longer, correlates to a higher probability of relapse-free survival. Gender, age, and other variables, such as Sokal scores, do not predict the probability of successful stopping.
“With inclusion and relapse criteria less strict than in many previous trials, and with decentralized but standardized PCR monitoring, stopping of TKI therapy in a large cohort of CML patients appears feasible and safe,” Dr Mahon said. “This trial demonstrates that half of patients are still off treatment without molecular recurrence after a median 15 months.”
Current guidelines recommend that most patients who achieve remission with TKI therapy continue taking the drugs indefinitely, yet it is unclear whether continued therapy is necessary for all patients.
The European Leukemia Net are expected to propose new guidelines in the next 6 months, which Dr Mahon hopes will define a consensus regarding durability of TKI therapy and provide recommendations on whether stopping TKIs can be moved into the clinic for appropriate patients.
*Information presented at the meeting differs from the abstract.