The role of stem cell transplantation in the management of Philadelphia chromosome-positive acute lymphoblastic leukemia

Post-transplant TKIs for Ph+ ALL: practices to date and clinical significance

Post-transplant tyrosine kinase inhibitors (TKIs) show promise in preventing relapse after allogeneic hematopoietic cell transplantation (allo-HCT) for Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ALL). However, their real-world use and efficacy remain unclear. A comprehensive study across seven centers included Ph+ALL patients who underwent allo-HCT between 2002 and 2022. Post-transplant TKIs were administered in 28% of patients (49 of 173 transplanted in complete remission): 7% as prophylaxis during complete molecular remission (CMR), and 21% in response to measurable residual disease (MRD) positivity. Median first post-transplant TKI duration was 13.7 months for the prophylactic group and 4.0 months for the MRD-triggered group. Prophylactic TKIs appear particularly beneficial for patients not in CMR at allo-HCT, showing a trend towards higher 5-year relapse-free survival (RFS) compared to those not receiving prophylactic TKIs (100% vs. 73%; P = 0.11). Significant RFS differences were observed between the prophylactic, non-TKI, and MRD-triggered groups. However, patients with white blood cell counts <15000/µl at diagnosis and no additional chromosomal abnormalities-an MRD-triggered high efficacy cluster-demonstrated comparable 5-year RFS regardless of TKI strategy (100% vs. 85% vs. 80%; P = 0.87). This cluster highlights the potential effectiveness of MRD-triggered TKI administration in select low-risk patients, suggesting tailored TKI strategies based on risk factors.

How to Manage Philadelphia-Positive Acute Lymphoblastic Leukemia in Resource-Constrained Settings

Recent studies have indicated that more than half of adult patients newly diagnosed with Ph+ ALL can now achieve a cure. However, determining the most suitable protocol for less-resourced settings can be challenging. In these situations, we must consider the potential for treatment toxicity and limited access to newer agents and alloSCT facilities. Currently, it is advisable to use less intensive induction regimens for Ph+ ALL. These regimens can achieve high rates of complete remission while causing fewer induction deaths. For consolidation therapy, chemotherapy should remain relatively intensive, with careful monitoring of the BCR-ABL1 molecular transcript and minimal residual disease. AlloSCT may be considered, especially for patients who do not achieve complete molecular remission or have high-risk genetic abnormalities, such as IKZF1-plus. If there is a loss of molecular response, it is essential to screen patients for ABL mutations and, ideally, change the TKI therapy. The T315I mutation is the most common mechanism for disease resistance, being targetable to ponatinib. Blinatumomab, a bispecific antibody, has shown significant synergy with TKIs in treating this disease. It serves as an excellent salvage therapy, aside from achieving outstanding results when incorporated into the frontline.