Acute Lymphoid Leukemia¶
Chapter 111 | Part 4: Oncology and Hematology
KEY CLINICAL POINTS¶
- ALL is the most common cancer in children, with peak incidence at 3–4 years; adult incidence ranges 0.7–1.8/100,000/year
- Philadelphia chromosome (Ph+) ALL is common in elderly B-lineage patients (50% of cases), while Ph-like ALL (BCR-ABL1-like) occurs in 10–30% of adults
- Minimal residual disease (MRD) negativity is the strongest prognostic factor, with MRD-negative patients achieving ~70% disease-free survival
- Targeted therapies (TKIs, CAR T-cells) and stem cell transplantation (SCT) are critical for high-risk and Ph+ ALL
- CNS prophylaxis with intrathecal chemotherapy and cranial irradiation is essential to prevent central nervous system relapse
1. DEFINITION & OVERVIEW¶
Acute lymphoblastic leukemia (ALL) is a clonal hematopoietic stem cell disorder characterized by uncontrolled proliferation of immature lymphoid blasts in the bone marrow and peripheral blood. The disease leads to bone marrow failure, immune dysfunction, and systemic infiltration.
Table 111-1 Laboratory Values at Diagnosis of Acute Lymphoblastic Leukemia (ALL)¶
| Parameter | Range | Percentage |
|---|---|---|
| Initial white blood cell count (×10n/L) | <10 | 41% |
| 10–50 | 31% | |
| >50–100 | 28% | |
| >100 | 16% | |
| Neutrophils (×10n/L) | <50–100 | 12% |
| <100,000 | 16% | |
| Platelets (×10n/L) | <20 | 22% |
| 21–40 | 22% | |
| 41–100 | 29% | |
| >100 | 27% | |
| Hemoglobin (g/dL) | <7 | 20% |
| 7–9 | 33% | |
| >9 | 47% |
| Parameter | Range | Percentage |
|---|---|---|
| Leukemic blasts in peripheral blood | 0% | 8% |
| 25–75% | 34% | |
| >75% | 36% | |
| Leukemic blasts in bone marrow | <50% | 4% |
| 51–90% | 25% | |
| >90% | 71% |
1.1 Pathogenesis¶
Malignant clone arises from hematopoietic progenitors in bone marrow or lymphatic system. Infiltration causes anemia, granulocytopenia, and thrombocytopenia. Symptoms often precede tumor bulk manifestations.
1.2 Diagnostic Criteria¶
Diagnosis confirmed by peripheral blood and bone marrow examination. Cytochemical stains, immunophenotyping, and cytogenetic analysis are required for classification.
2. EPIDEMIOLOGY¶
ALL is the most frequent neoplastic disease in children with peak incidence at 3–4 years. Adult incidence ranges 0.7–1.8/100,000/year, higher in adolescents and young adults (AYAs), decreasing with age but increasing again in elderly. Down syndrome patients have 20-fold increased leukemia risk.
2.1 Demographics¶
Children: peak 3–4 years; Adults: 0.7–1.8/100,000/year. Elderly patients ( ≥ 60 years) have higher Ph+ ALL incidence (50% of B-lineage cases).
2.2 Risk Factors¶
Ionizing radiation, chemotherapy, and certain congenital disorders (e.g., Down syndrome, Fanconi’s anemia) increase risk. Second malignancies after prior chemotherapy are common.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
Etiology is multifactorial with genetic and environmental influences. Congenital syndromes (e.g., Klinefelter’s, ataxia-telangiectasia) increase risk. Viral associations (EBV, HTLV-1) are implicated in rare cases.
Table 111-2 Immunologic, Cytogenetic, Molecular, and Clinical Characteristics of Adult ALL¶
| Subtype | Marker | Incidence | Cytogenetic Aberrations | Clinical Characteristics | Relapse Kinetic s/Localization |
|---|---|---|---|---|---|
| B-lineage ALL (B-ALL) | HLA-DR+, TdT+, CD19+, CD79a+, cyCD22+ | 76% | t(4;11), t(9;22), del(6q) | High WBC (>100,000/mL), mainly BM | Prolonged relapse kinetics (5–7 years) |
| Subtype | Marker | Incidence | Cytogenetic Aberrations | Clinical Characteristics | Relapse Kinetic s/Localization |
|---|---|---|---|---|---|
| Common ALL | CD10+ | 49% | t(9;22), del(6q) | Higher age >50 years, mainly BM | Prolonged relapse kinetics |
| Pre-B-ALL | CD10±, cyIg+ | 12% | t(9;22), t(1;19) | Younger age, frequent CNS involvement | Short relapse kinetics (1–1.5 years) |
| Mature B-ALL | TdT–, CD34–, sIg+ | 4% | t(8;14), t(2;8), t(8;22) | Higher age >55 years, frequent organ involvement | Short relapse kinetics |
| T-lineage ALL | TdT±, cyCD3, CD7+ | 24% | t(10;14), t(11;14), NOTCH1 mutations | Younger age (<50 years), frequent mediastinal tumors | Intermediate relapse kinetics (3–4 years) |
| Early Pro/Pre T-ALL | No additional differentiation markers | 6–12% | Various | High WBC (>50/mL), frequent CNS | Fast progression on relapse |
3.1 Genetic Aberrations¶
Ph+ ALL (BCR-ABL translocation) and Ph-like ALL (IKZF1 deletion, JAK2/PDGFRB mutations) are critical. Molecular profiling identifies ETP-ALL and other subtypes.
3.2 Bone Marrow Involvement¶
Bone marrow is heavily infiltrated with blasts (>90% in 70% of patients). Normal hematopoiesis is suppressed, leading to pancytopenia.
4. CLINICAL FEATURES¶
Symptoms include fatigue, weakness, infection, and hemorrhage due to pancytopenia. CNS involvement (meningeal leukemia) may present with headache, vomiting, or spinal fluid abnormalities. Organ infiltration (e.g., mediastinal tumors) is common in T-ALL.
4.1 Presentation¶
Fatigue, weakness, infection, and bleeding are most common. CNS symptoms (e.g., headache, vomiting) occur in 5–10% of adults. Mediastinal masses are frequent in T-ALL.
4.2 Complications¶
Tumor lysis syndrome, infections, bleeding, and CNS relapse. Extramedullary disease (e.g., testicular, skin) is common in Ph+ ALL.
5. DIFFERENTIAL DIAGNOSIS¶
Other leukemias (AML, chronic lymphocytic leukemia), infections (viral, bacterial), and lymphomas must be differentiated. Bone marrow biopsy and flow cytometry are critical for diagnosis.
5.1 Key Differentiators¶
ALL vs AML: Immature blasts in peripheral blood, lymphoid markers (CD10, CD19) vs myeloid markers. CNS involvement is more common in ALL.
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnosis requires peripheral blood smear, bone marrow biopsy, lumbar puncture, and flow cytometry. Cytogenetic and molecular analysis (e.g., BCR-ABL, MLL-AF4) are essential for risk stratification.
Table 111-3 Response Parameters According to Minimal Residual Disease (MRD)¶
| Term | Definition |
|---|---|
| Complete hematologic remission (CHR) | Leukemic cells not detectable by light microscopy (<5% blast cells in BM) |
| Complete molecular remission/MRD negativity | MRD not detectable, £0.01% = £1 leukemia cell in 10,000 BM cells |
| Molecular failure/MRD positivity | Patient in complete hematologic remission but not in molecular remission (>0.01%) |
| Molecular relapse/MRD positivity | Patient still in complete remission but with prior molecular remission, leukemic blasts in BM not detectable (<5%) |
| Hematologic relapse | ‡5% blast cells in BM/blood |
6.1 Diagnostic Tests¶
Peripheral blood counts, bone marrow aspiration/biopsy, lumbar puncture, and flow cytometry. Cytogenetic analysis identifies Ph+ and Ph-like ALL.
6.2 MRD Detection¶
MRD is detected by flow cytometry, PCR for rearranged immunoglobulin/T-cell receptor genes, or NGS. Sensitivity ranges 10 I ³–10 II .
7. MANAGEMENT & TREATMENT¶
Treatment includes pre-phase therapy, induction, consolidation, and maintenance. Targeted therapies (TKIs, CAR T-cells) and SCT are critical for high-risk and Ph+ ALL. CNS prophylaxis is essential.
Table 111-4 Best Results in Recent Studies for Adult ALL¶
| Subtype | Treatment | Overall Survival |
|---|---|---|
| Burkitt’s leukemia | Short intensive chemotherapy + rituximab; no SCT; no maintenance | 80–90% |
| B-lineage ALL, Ph– | Intensive chemotherapy +/– SCT | 50–60% (Adults 45–55 years) |
| Ph BCR-ABL | Intensive chemotherapy + TKI +/– SCT | 60–70% |
| Ph-like ALL | Chemotherapy + dasatinib/JAK inhibitors | £50% |
| T-lineage ALL | Intensive chemotherapy + nelarabine + SCT | 40–50% |
| Mature T-ALL | Intensive chemotherapy + nelarabine + SCT | 30–50% |
7.1 Treatment Regimens¶
BFM-like regimens (e.g., vincristine, prednisone, anthracyclines) and Hyper-CVAD protocols. Intensive chemotherapy with asparaginase and corticosteroids.
7.2 Stem Cell Transplantation¶
SCT is recommended for high-risk patients and Ph+ ALL. Allogeneic SCT improves survival to 50–70% in first CR. Autologous SCT is limited to MRD-negative patients.
7.3 Targeted Therapies¶
TKIs (dasatinib, ponatinib) for Ph+ and Ph-like ALL. CAR T-cells (CD19-targeted) for CNS relapse. Monoclonal antibodies (rituximab, blinatumomab) for B-ALL.
8. PROGNOSIS & COMPLICATIONS¶
Childhood ALL has ~90% cure rate; elderly patients (<10% survival). CNS relapse is common (2–5%) and requires aggressive treatment. Extramedullary disease and resistance to therapy are significant challenges.
8.1 Risk Stratification¶
Standard-risk patients have no risk factors; high-risk patients have MRD positivity, age >50, or Ph+ status. MRD negativity is the strongest prognostic factor.
8.2 Complications¶
CNS relapse, treatment-related mortality, and extramedullary disease. Ph-like ALL has poor prognosis despite targeted therapies.
9. SPECIAL CONSIDERATIONS¶
Pregnancy requires modified chemotherapy regimens. Elderly patients benefit from less-intensive protocols with glucocorticoids, vincristine, and asparaginase. CAR T-cells and TKIs are effective in CNS relapse.
9.1 Pediatric vs Adult Treatment¶
Pediatric-inspired regimens use higher doses of glucocorticoids and asparaginase with fewer myeloablative agents. AYAs have ~70–80% survival with optimized protocols.
9.2 Elderly Patients¶
Less-intensive protocols with glucocorticoids, vincristine, and asparaginase improve outcomes. Early death rate <10% with optimized supportive care.
10. KEY POINTS & CLINICAL PEARLS¶
- MRD negativity is the strongest prognostic factor in ALL
- Ph+ ALL responds best to TKIs (dasatinib, ponatinib)
- CNS prophylaxis is critical to prevent relapse
- CAR T-cells and blinatumomab are effective for CNS relapse
- Elderly ALL patients benefit from less-intensive, non-anthracycline-based regimens