Sequential Treatments in Chronic Phase Chronic Myeloid Leukemia (CML) Patients without Optimal Response after Frontline Nilotinib or Dasatinib: An Italian CML Campus Study

INTRODUCTION: Frontline therapy with second generation (2G) tyrosine-kinase inhibitors (TKIs) in chronic phase (CP) chronic myeloid leukemia (CML) patients demonstrated higher efficacy as compared to imatinib, with less patients experiencing treatment failure and progression to advanced disease. However, limited information are currently available on the management and outcome of those CML pts not achieving an optimal response to first-line treatment with a 2G-TKI.

AIM: To describe the clinical outcome of CP CML patients without an optimal response to a frontline 2G-TKI that switched to alternative TKIs.

METHODS: We performed a retrospective analysis in 22 Centers cooperating within the Italian CML Campus Project. Main inclusion criteria were: 1) diagnosis of CP-CML after 2010; 2) first-line treatment with a 2G-TKI; 3) switch to second-line treatment in case of non-optimal response (either following ELN recommendations or as for clinical practice); 4) CML in CP at the time of switching to second-line treatment. The main exclusion criteria were a switch to second-line treatment for intolerance or for low adherence to therapy.

RESULTS: The main findings of this analysis are summarized in the table. Seventy-one pts meeting the inclusion/exclusion criteria were identified; the median age of pts at CML diagnosis was 46 (21-80) years. Sokal risk score was low, intermediate, and high in 24 (34%), 30 (42%), and 17 (24%) pts, respectively. First-line treatment was performed with nilotinib in 47 (66%) pts and dasatinib in 24 (34%) pts. According to the ELN 2020 recommendations, 51 (72%) pts fulfilled the criteria for "failure" and 20 (28%) pts those for "warning". BCR-ABL mutations were identified in 12 of 65 (18%) evaluable pts (T315I in 1 pt). Additional chromosomal abnormalities in Ph+ cells were identified in 6 of 54 (11%) evaluable pts.

Second-line treatment was started after a median time of 16 (4-72) months, with ponatinib (40 pts, 56%), dasatinib (21 pts, 30%), nilotinib (7 pts, 10%), or bosutinib (3 pts, 4%). Median follow-up from start of second-line treatment was 25 (2-90) months. Best response to second-line treatment was MR2 in 18 (25%) pts and MR3 in 37 (51%) pts.

Nineteen (27%) pts (13 for resistance and 6 for intolerance) switched to third-line treatment (ponatinib, 11 pts; nilotinib, 3 pts; dasatinib, 4 pts; imatinib, 1 pt), after a median time of 8 (1-72) months. Mutations were identified in 2 of 17 evaluable pts, and both patients harbored a T315I mutation. MR3 was reached by 9 (47%) of these pts. Lastly, 7 (10%) pts switched (6 for resistance and 1 for intolerance) to fourth-line treatment (asciminib, 4pts; dasatinib, 2 pts, nilotinib, 1 pt).

Overall, 44 (62%) patients reached with sequential TKI treatments a MR3 (31/51 pts among "failures"; 13/20 among "warnings"). Allogeneic stem-cell transplantation (SCT) was performed in 7 (9.5%) pts (6 among "failures"), after a median time of 20 (15-60) months from CML diagnosis. Progression to advanced phase occurred in 2 (3%) pts; both pts previously met the ELN2020 "failure" criteria. Estimated 4-y PFS was 92.5%. Death occurred in 3 (4%) pts (1 after progression to blast phase, 2 for cardiovascular adverse events). Estimated 4-y OS was 93.7%

CONCLUSION

Our findings show that CP-CML patients not achieving an optimal response to frontline 2G-TKI therapy, despite a complex management, still have a favorable prognosis and survival due to the availability of both multiple TKI options and SCT.

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