A randomized, phase II trial of adjuvant immunotherapy with durable TKI-free survival in patients with chronic phase CML.

PURPOSE

Chronic myeloid leukemia (CP-CML) patients can achieve undetectable minimal residual disease (UMRD) and discontinue tyrosine kinase inhibitors (TKIs). Cellular immunity plays an important role in CML disease control. We conducted a randomized, non-blinded phase II trial of adjuvant immunotherapy with TKIs to facilitate TKI discontinuation.

METHODS

TKI-treated patients with CP-CML were randomized to receive the K562/GM-CSF vaccine (vaccine) OR Interferon-α + Sargramostim (IFN). If UMRD was achieved, then all treatment was stopped. Patients who did not achieve UMRD within one year, had a molecular relapse, or discontinued therapy for toxicity could crossover.

RESULTS

Thirty-four patients were randomized to IFN (n = 18) or vaccine (n = 16), and 21 patients crossed over (IFN⟶vaccine: n = 9, vaccine⟶IFN, n = 12). TKIs at enrollment included imatinib (n = 31), nilotinib (n = 2), and dasatinib (n = 1). No patients discontinued vaccine due to side effects, while 33 % of IFN-treated patients discontinued treatment. More patients randomized to IFN (47.4 %, 95 % CI: 16.7-66.7 %) versus vaccine (25.0 %, 95 % CI: 0.5-43.5 %) achieved UMRD within one year. Seven patients randomized to IFN discontinued treatment with 28.6 % (95 % CI: 8.9-92.2 %) sustaining treatment-free remission (TFR) at 1 year, while three patients randomized to vaccine discontinued treatment with none sustaining TFR. Including crossover, there was a cumulative discontinuation success rate of 36.4 % (95 % CI: 16.6 %-79.5 %) after adjuvant IFN. Patients who sustained TFR received a median of 29 months of imatinib prior to discontinuation.

CONCLUSION

Adjuvant IFN led to durable TFRs with limited prior TKI exposure with comparable success to prior discontinuation trials, but many patients stopped IFN early.