In a patient with acute lymphoblastic leukemia (ALL) who has relapsed after an allogeneic stem‑cell transplant, what is the recommended approach and dosing schedule for donor lymphocyte infusion (DLI) while ensuring adequate organ function and no active severe graft‑versus‑host disease (GVHD)?

DLI in Acute Lymphoblastic Leukemia After Allogeneic Transplant

Donor lymphocyte infusion (DLI) has very limited efficacy in relapsed ALL after allogeneic transplant and should be combined with cytoreductive chemotherapy, though even this approach rarely produces durable remissions. 1

Key Evidence on DLI Efficacy in ALL

The fundamental challenge with DLI in ALL is that this disease demonstrates intrinsic resistance to graft-versus-leukemia (GVL) effects, unlike CML where DLI is highly effective 2. A prospective study of chemotherapy followed by G-CSF-primed DLI in 10 relapsed ALL patients showed:

• 70% achieved complete remission (CR rate of 7/10 patients)
• Only 1 patient remained alive in CR long-term (907 days post-DLI)
• Median survival was just 175 days after DLI
• Most CR patients relapsed within 120-991 days 1

This poor outcome appears primarily due to resistance to GVL effect rather than rapid disease pace 1.

Recommended Approach for Post-Transplant ALL Relapse

For Philadelphia-Positive ALL:

Combine second-generation tyrosine kinase inhibitors (TKIs) with DLI rather than using DLI alone:

• Use nilotinib or dasatinib (not imatinib if previously failed) 3
• Add monthly DLI infusions to the TKI
• This combination can achieve complete molecular remission even in imatinib-resistant disease 3
• Standard dose nilotinib with DLI is well-tolerated 3

For Philadelphia-Negative ALL:

The evidence strongly suggests DLI alone is insufficient. Consider this algorithm:

1. First-line approach: Salvage chemotherapy (intermediate-dose cytarabine + anthracycline ± purine analogue) followed immediately by G-CSF-primed DLI 1

2. Alternative for late relapse (>5 months post-transplant): Second allogeneic transplant or DLI may induce long-term survival, particularly if relapse occurs >5 months after first transplant 4

3. Timing matters critically: Survival probabilities at 3 years are only 4% for relapse within 6 months, but improve to 12% (6-24 months), 26% (2-3 years), and 38% (>3 years) after initial transplant 4

DLI Dosing and Administration

Based on recent multicenter data for acute leukemia (including ALL):

Prophylactic DLI (if considering prevention):

• Timing: Median 50-51 days post-transplant 5, 6
• Starting dose: 0.1 × 10⁶ CD3+ T cells/kg 5
• Median number: 1 infusion (range 1-2.5) 5
• Note: Prophylactic DLI shows benefit in AML but ALL-specific data is limited

Therapeutic DLI (for active relapse):

• Starting dose: 1 × 10⁶ CD3+ T cells/kg 5
• For matched sibling donors: Can safely use up to 1 × 10⁶ CD3+ cells/kg 7
• For mismatched/haploidentical donors: Start lower at 1 × 10⁵ CD3+ cells/kg 7
• Escalation strategy: Use escalating doses to minimize overwhelming GVHD 8

Preemptive DLI (for MRD positivity):

• Trigger: MRD >0.1% blasts 6
• Dose: 0.5 × 10⁶ CD3+ T cells/kg 5
• Median number: 2 infusions (range 1-3) 5

Critical Prerequisites Before DLI

Absolute requirements:

• No active severe (grade III-IV) acute GVHD
• Adequate organ function
• No active uncontrolled infection

Strongly consider tapering or withdrawing immunosuppression before DLI administration 2, 9.

Expected Outcomes and Toxicity

GVHD Risk:

• Acute GVHD (grade II-IV): 17-29% 8, 5
• Chronic GVHD: 21-53% depending on indication (highest with prophylactic use at 53%) 5
• Severe acute GVHD: 13-14% at appropriate doses 7

Survival Expectations:

• Prophylactic DLI: 61% OS after first DLI 5
• Preemptive DLI: 40% OS after first DLI 5
• Therapeutic DLI (active disease): 22% OS after first DLI 5

Critical Pitfalls to Avoid

1. Do not use DLI alone in ALL relapse - it has minimal efficacy as monotherapy 1

2. Do not delay too long - relapse within 6 months post-transplant has dismal outcomes even with intervention 4

3. Do not use standard doses in mismatched/haploidentical settings - start 10-fold lower than matched sibling doses 7

4. Do not expect CML-like responses - ALL is fundamentally resistant to GVL effects 1

5. For Ph+ ALL, do not use imatinib if previously failed - switch to nilotinib or dasatinib 3

Alternative Considerations

Given the poor outcomes with DLI in ALL, strongly consider second allogeneic transplant for patients who:

• Relapse >5 months after first transplant
• Achieve CR with salvage chemotherapy
• Have adequate performance status 4

Hypomethylating agents (azacitidine) represent a less toxic alternative, particularly for relapses >6 months post-transplant, though this is better established in AML than ALL 4.