Chronic Lymphocytic Leukemia¶
Chapter 112 | Part 4: Oncology and Hematology
KEY CLINICAL POINTS¶
- CLL is a heterogeneous B-cell malignancy with variable clinical course, ranging from indolent to aggressive disease.
- Minimal residual disease (MRD) negativity is a critical prognostic factor and treatment response marker, associated with improved survival.
- Targeted therapies (BTK inhibitors, BCL2 inhibitors, CAR-T) have transformed CLL management, offering durable remissions and improved outcomes.
- Richter's transformation to aggressive lymphoma is a devastating complication, with distinct clinical and therapeutic implications.
- Monoclonal B-cell lymphocytosis (MBL) is a precursor state to CLL, with low-risk progression to overt disease.
1. DEFINITION & OVERVIEW¶
Chronic lymphocytic leukemia (CLL) is a monoclonal proliferation of mature B lymphocytes characterized by an absolute number of malignant cells in the blood ≥ 5 × 10 I /L. It is defined by the presence of clonal B cells in the blood without nodal, spleen, or liver involvement and absent cytopenias. Monoclonal B-cell lymphocytosis (MBL) is a precursor state with <5 × 10 I /L clonal B cells.
Table 112-1: Recurrent Mutations in CLL¶
| GENE | FREQUENCY OF MUTATIONS (%) |
|---|---|
| SF3B1 | 8–14 |
| TP53 | 5–13 |
| NOTCH1 | 10–13 |
| MYD88 | 4–8 |
| ATM | 8–11 |
| BIRC3 | <5 |
| XPO1 | <5 |
| FBXW7 | <5 |
| POT1 | <5 |
| BRAF | <5 |
| EGR2 | <5 |
| IKZF3 | <5 |
1.1 Diagnostic Criteria¶
Diagnosis requires ≥ 5 × 10 I /L clonal B cells in peripheral blood with characteristic immunophenotype (CD19+, CD20+, CD23+, CD5+, dim surface Ig). MBL is defined by <5 × 10 I /L clonal B cells without clinical features of CLL.
1.2 Disease Heterogeneity¶
CLL exhibits a wide clinical spectrum, with indolent disease in ~70% of patients and aggressive disease in ~30%. Prognosis is influenced by genetic and molecular features, including IGHV mutation status and cytogenetic abnormalities.
2. EPIDEMIOLOGY¶
CLL is primarily a disease of older adults, with median age at diagnosis 71 years. Age-adjusted incidence in the U.S. is 4.6/100,000. Male-to-female ratio is 2:1, becoming more equal with age. Incidence increases with age, with ~12% prevalence in the general population. MBL (monoclonal B-cell lymphocytosis) is common in first-degree relatives of CLL patients (18% frequency).
Table 112-3: Staging of CLL¶
| Rai Staging System | Binet Staging System |
|---|---|
| Low risk (stage 0): Lymphocytosis only | A <3 areas of lymphadenopathy |
| Intermediate risk (stage I/II): Lymphocytosis with lymphadenopathy | B ‡3 areas of lymphadenopathy |
| High risk (stage III/IV): Lymphocytosis with anemia/thrombocytopenia | C Hemoglobin £10 g/dL and/or platelets <100,000/mL |
2.1 Risk Factors¶
Genetic predisposition (family history), IGHV unmutated status, del(17)(p13.1), and certain environmental exposures (e.g., Agent Orange).
2.2 Demographics¶
Most common in Caucasians, less common in Hispanic and African Americans, rare in Asians. Incidence peaks in 7th decade of life.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
CLL arises from clonal expansion of mature B cells with dysregulated B-cell receptor (BCR) signaling. Key pathogenic mechanisms include IGHV mutation status, BTK inhibition, and genomic abnormalities (e.g., del(13)(q14.3), trisomy 12).
Table 112-2: Typical Immunophenotype of CLL¶
| DISEASE | CD5 | CD10 | CD19 | CD20 | CD23 | CYCLIN D1 | SURFACE IG |
|---|---|---|---|---|---|---|---|
| CLL | + | - | + | + (dim) | + | - | + (dim) |
| Mantle cell lymphoma | + | - | + | + (mod/brig ht) | - | + | + (mod/brig ht) |
| Marginal zone lymphoma | -/+ | - | + | + (mod/brig ht) | -/+ | - | + (mod/brig ht) |
| DISEASE | CD5 | CD10 | CD19 | CD20 | CD23 | CYCLIN D1 | SURFACE IG |
|---|---|---|---|---|---|---|---|
| Follicular lymphoma | - | + | + | + | + | - | + |
3.1 BCR Signaling Abnormalities¶
Low-level IgM expression, tonic BCR signaling, and constitutive activation of antiapoptotic pathways (e.g., NF- κ B) drive CLL pathogenesis. IGHV mutation status correlates with disease course (mutated vs. unmutated).
3.2 Cytogenetic Abnormalities¶
Common abnormalities include del(13)(q14.3), trisomy 12, del(11)(q22.3), and del(17)(p13.1). del(17)(p13.1) is associated with poor prognosis and TP53 dysfunction.
4. CLINICAL FEATURES¶
Most patients present incidentally with elevated lymphocyte counts. Symptomatic disease includes fatigue, weight loss, night sweats, and lymphadenopathy. Complications include infections, autoimmune cytopenias, and Richter's transformation.
Table 112-5: Criteria for Initiation of Therapy¶
| Symptoms Indicating Need for Therapy |
|---|
| Progressive marrow failure (worsening anemia/thrombocytopenia) |
| Massive splenomegaly (>6 cm below costal margin) |
| Massive lymphadenopathy (>10 cm) |
| Lymphocytosis doubling time <6 months |
| Autoimmune cytopenias unresponsive to standard therapy |
| Symptomatic extranodal involvement |
| Constitutional symptoms (unintentional weight loss, fever, night sweats) |
4.1 Common Symptoms¶
Fatigue, unintentional weight loss (>10% over 6 months), fevers, night sweats, and lymphadenopathy. Constitutional symptoms are common in advanced disease.
4.2 Complications¶
Infections (30–50% of deaths), autoimmune cytopenias (AIHA, ITP), secondary cancers, and Richter's transformation to DLBCL or Hodgkin lymphoma.
5. DIFFERENTIAL DIAGNOSIS¶
Differential diagnosis includes monoclonal B-cell lymphocytosis (MBL), small lymphocytic lymphoma (SLL), and other B-cell malignancies (e.g., mantle cell lymphoma, follicular lymphoma).
5.1 MBL vs. CLL¶
MBL is defined by <5 × 10 I /L clonal B cells without clinical features of CLL. CLL is diagnosed when clonal B cells ≥ 5 × 10 I /L with characteristic immunophenotype.
5.2 SLL vs. CLL¶
SLL is a tissue-based disease with lymph node involvement, while CLL is primarily bone marrow/blood-based. Both share identical genetic features.
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnosis requires flow cytometry to confirm clonal B-cell proliferation, FISH for cytogenetic abnormalities, and immunophenotyping. MRD assessment is critical for treatment response evaluation.
Table 112-6: Response Criteria in CLL¶
| LYMPHOCYTE COUNT | LYMPH NODES | SPLEEN/LIVER SIZE | BONE MARROW | PERIPHERAL BLOOD COUNTS |
|---|---|---|---|---|
| CR: <4000/mL | None >1.5 cm | Not palpable | Normocellular, <30% lymphoid nodules | Platelet count >100,000/mL |
| PR: ‡50% decrease from baseline | ‡50% decrease from baseline | ‡50% decrease from baseline | Infiltrate £50% of baseline | Hemoglobin >11 g/dL |
| Stable disease | Not meeting CR/PR/PD criteria | Not meeting CR/PR/PD criteria | Not meeting CR/PR/PD criteria | Neutrophils >1500/mL |
| PD: ‡50% increase from baseline | ‡50% increase from baseline | ‡50% increase from baseline | Infiltrate >50% of baseline | Platelet count £50% of baseline |
6.1 Diagnostic Tests¶
Flow cytometry (CD19+, CD20+, CD23+, CD5+), FISH for del(13)(q14.3), trisomy 12, del(11)(q22.3), and del(17)(p13.1), and sequencing for TP53 and IGHV mutation status.
6.2 MRD Assessment¶
MRD negativity ( ≤ 0.01% CLL cells in 10 I leukocytes) is a key prognostic factor. Next-generation sequencing (e.g., ClonoSeq) is used for sensitive detection.
7. MANAGEMENT & TREATMENT¶
Treatment is guided by risk stratification and MRD status. First-line therapy includes BTK inhibitors (e.g., ibrutinib, acalabrutinib, zanubrutinib) and BCL2 inhibitors (venetoclax). CAR-T and allogeneic stem cell transplant are used in high-risk cases.
Table 112-4: CLL International Prognostic Index¶
| RISK SCORE | VARIABLE | ADVERSE FACTOR |
|---|---|---|
| 4 | TP53 status | Deleted or mutated |
| 2 | b-Microglobulin | >3.5 mg/L |
| 2 | Clinical stage | Rai I–IV or Binet B–C |
| 1 | Age | >65 years |
7.1 First-Line Therapy¶
Oral targeted therapies (BTK inhibitors + anti-CD20 monoclonal antibodies) are preferred. Chemoimmunotherapy (FCR or BR) is used in younger patients with favorable cytogenetics.
7.2 Relapsed/Refractory CLL¶
Combination therapies (e.g., venetoclax + obinutuzumab) are used. CAR-T and allogeneic stem cell transplant are considered for high-risk patients. MRD-directed strategies are critical.
8. PROGNOSIS & COMPLICATIONS¶
Prognosis is influenced by IGHV mutation status, cytogenetics, and MRD. Complications include infections, autoimmune cytopenias, and Richter's transformation. Five-year survival varies from 93.2% (low-risk) to 23.3% (very high-risk).
8.1 Prognostic Factors¶
IGHV unmutated status, del(17)(p13.1), TP53 mutations, and high β -microglobulin are associated with poor prognosis. MRD negativity correlates with improved survival.
8.2 Richter's Transformation¶
Transformation to DLBCL or Hodgkin lymphoma occurs in ~0.5–1% per year. SUV >5 on PET/CT is suspicious, while SUV ≥ 10 is highly concerning.
9. SPECIAL CONSIDERATIONS¶
Management in special populations includes vaccination strategies, monitoring for secondary cancers, and addressing autoimmune complications. MBL is managed with vaccinations and cancer screening.
9.1 Vaccination¶
Annual influenza, pneumococcal, and varicella-zoster vaccines are recommended. Live vaccines should be avoided due to immunosuppression.
9.2 Pregnancy¶
Avoid live vaccines during pregnancy. Targeted therapies (e.g., BTK inhibitors) are generally avoided in pregnancy due to potential teratogenicity.
10. KEY POINTS & CLINICAL PEARLS¶
- MRD negativity is a critical endpoint in CLL treatment. 2. BTK and BCL2 inhibitors have transformed CLL management. 3. Richter's transformation is a major complication requiring aggressive therapy. 4. MBL is a precursor state with low-risk progression. 5. Vaccination and cancer screening are essential for long-term management.