Which chromosomal translocation in acute leukemia is associated with the best prognosis and is a target for fusion protein-directed therapy?

Question

Accepted Answer

B. t(15;17) in acute promyelocytic leukemia. ## Prognostically Favorable Translocations in Acute Leukemias

**Key Point:** t(15;17) in APL creates the PML-RARA fusion gene, which is highly responsive to ATRA (all-trans retinoic acid) and arsenic trioxide, resulting in cure rates >90% — the best prognosis among acute leukemias.

### t(15;17) in Acute Promyelocytic Leukemia (APL)

**High-Yield:** APL with t(15;17) is the **only acute leukemia with a targeted fusion protein therapy** that has transformed it from a fatal disease to a highly curable malignancy.

#### Mechanism of ATRA and Arsenic Trioxide
1. **ATRA (all-trans retinoic acid):** Binds to the PML-RARA fusion protein and promotes differentiation of leukemic promyelocytes into mature neutrophils, leading to terminal differentiation and apoptosis.
2. **Arsenic trioxide:** Induces degradation of the PML-RARA fusion protein through proteasomal and autophagy pathways, triggering apoptosis of leukemic cells.
3. **Synergistic effect:** Combined ATRA + arsenic trioxide achieves complete remission in >95% of patients and long-term disease-free survival in >90%.

### Comparison of Prognostically Important Translocations

| Translocation | Leukemia Type | Fusion Gene | Prognosis | Targeted Therapy |
| --- | --- | --- | --- | --- |
| **t(15;17)** | **APL** | **PML-RARA** | **Excellent (>90% cure)** | **ATRA + arsenic trioxide** |
| t(9;22) | ALL, CML | BCR-ABL | Poor in ALL (without TKI); improved with imatinib | Tyrosine kinase inhibitors |
| t(8;14) | Burkitt leukemia/lymphoma | MYC-IGH | Intermediate (depends on age, LDH) | Intensive chemotherapy |
| t(4;11) | ALL (especially infant ALL) | KMT2A-AFF1 | Very poor (especially in infants) | Intensive chemotherapy, experimental agents |

**Clinical Pearl:** APL is a medical emergency presenting with disseminated intravascular coagulation (DIC) due to release of procoagulant from abnormal promyelocytes. However, once ATRA is started, DIC resolves rapidly as leukemic cells differentiate, and cure is achievable — a remarkable success story in oncology.

**Mnemonic:** **APL = ATRA + Arsenic = Awesome prognosis** — Remember that t(15;17)/PML-RARA is the translocation with the best outcome in acute leukemia because it responds to fusion protein-targeted therapy.

Answer

A. t(4;11) in acute lymphoblastic leukemia

Answer

C. t(9;22) in acute lymphoblastic leukemia

Answer

D. t(8;14) in Burkitt lymphoma/leukemia

Which chromosomal translocation in acute leukemia is associated with the best prognosis and is a target for fusion protein-directed therapy?

Explanation

Prognostically Favorable Translocations in Acute Leukemias

t(15;17) in Acute Promyelocytic Leukemia (APL)

Mechanism of ATRA and Arsenic Trioxide

Comparison of Prognostically Important Translocations

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Translocation	Leukemia Type	Fusion Gene	Prognosis	Targeted Therapy
t(15;17)	APL	PML-RARA	Excellent (>90% cure)	ATRA + arsenic trioxide
t(9;22)	ALL, CML	BCR-ABL	Poor in ALL (without TKI); improved with imatinib	Tyrosine kinase inhibitors
t(8;14)	Burkitt leukemia/lymphoma	MYC-IGH	Intermediate (depends on age, LDH)	Intensive chemotherapy
t(4;11)	ALL (especially infant ALL)	KMT2A-AFF1	Very poor (especially in infants)	Intensive chemotherapy, experimental agents