iwCLL 2018International Workshop on CLL Standardized Assessment
Examination & Organ Response
Laboratory & Bone Marrow
Progression Alerts
Response Classification
Select the clinical and laboratory findings to determine the standardized iwCLL 2018 response category.
Guidelines & Evidence
Verified
Last Review: 2026
When to Use
What is iwCLL 2018?
The International Workshop on Chronic Lymphocytic Leukemia (iwCLL) published the updated 2018 guidelines to standardize response assessment in CLL clinical trials and clinical practice. These criteria replaced the 2008 (Hallek) and 1996 (Cheson) guidelines. The 2018 update reflects the paradigm shift from cytotoxic chemo-immunotherapy (FCR, BR, chlorambucil) to continuous targeted agents (BTK inhibitors: ibrutinib, acalabrutinib, zanubrutinib; BCL2 inhibitor: venetoclax; PI3K inhibitors: idelalisib, duvelisib) and fixed-duration combinations (venetoclax + obinutuzumab, ibrutinib + venetoclax). The criteria ensure global uniformity in clinical trial endpoints (ORR, CR rate, PFS, TTNT), which is critical for regulatory approval by FDA, EMA, and PMDA.
Primary Clinical Applications
Clinical trials endpoint assessment (phase 1-3) - primary endpoint often ORR (CR + PR) for single-arm trials, PFS for randomized trials
Individual patient management: determining response to therapy, timing of next-line treatment, and switching from ineffective regimens
Regulatory approval: FDA and EMA require iwCLL-defined response categories for CLL drug approvals
Comparative effectiveness research: allows pooling of data across trials and real-world cohorts using standardized definitions
Minimal residual disease (MRD) assessment integration: 2018 update incorporated MRD as a secondary endpoint
Richter transformation surveillance: new rapid symptomatic lymphadenopathy triggers biopsy
Key 2018 Updates vs 2008 Criteria
| Parameter | 2008 iwCLL Criteria | 2018 iwCLL Criteria | Clinical Rationale |
|---|---|---|---|
| Lymph node threshold for PR | ≥ 50% decrease from baseline | Same - ≥ 50% decrease | Remains robust predictor of response |
| CT imaging requirement for CR | Mandatory CT chest/abdomen/pelvis | Mandatory CT chest/abdomen/pelvis (same) | Detects mesenteric, retroperitoneal, or mediastinal nodes not palpable |
| CR with incomplete marrow recovery (CRi) | Allowed (PLT <100 or Hgb <11 if other CR criteria met) | Same - CRi retained | Distinguishes response from treatment-related myelosuppression vs residual CLL |
| MRD assessment | Not incorporated | Added as secondary endpoint (flow cytometry or PCR, threshold 10⁻⁴) | MRD negativity predicts longer PFS, especially with venetoclax |
| Richter Transformation definition | Mentioned but not formalized | Explicit definition with PET-CT SUVmax >5-10; biopsy required | Early detection enables aggressive therapy |
| Nodular Partial Response (nPR) | Bone marrow nodules but no CLL in blood/imaging | nPR retained | Distinguishes from CR when marrow shows lymphoid aggregates |
Response Categories
iwCLL 2018 Response Criteria - Complete Table
| Parameter | Complete Response (CR) | CRi | Partial Response (PR) | Progressive Disease (PD) | Stable Disease (SD) |
|---|---|---|---|---|---|
| Peripheral Blood Lymphocytes | < 4.0 x 10⁹/L | < 4.0 x 10⁹/L | ≥ 50% decrease from baseline | ≥ 50% increase from baseline OR new lymphocytosis >5 x 10⁹/L | Neither PR nor PD |
| Lymphadenopathy (CT or exam) | No nodes > 1.5 cm | No nodes > 1.5 cm | ≥ 50% decrease in SPD of up to 6 nodes | ≥ 50% increase in SPD OR new node >1.5 cm | Neither PR nor PD |
| Spleen (palpable) | Not palpable | Not palpable | ≥ 50% decrease in palpable enlargement | ≥ 50% increase OR new palpable spleen | Neither PR nor PD |
| Liver (palpable) | Not palpable | Not palpable | ≥ 50% decrease in palpable enlargement | ≥ 50% increase OR new hepatomegaly | Neither PR nor PD |
| Platelet Count | > 100 x 10⁹/L | < 100 x 10⁹/L (incomplete) | >100 OR ≥50% increase from baseline (if baseline <100) | Decrease ≥50% from baseline due to CLL | Neither PR nor PD |
| Hemoglobin | > 110 g/L (11 g/dL) | < 110 g/L (11 g/dL) | >110 OR ≥50% increase from baseline (if baseline <110) | Decrease ≥20 g/L from baseline due to CLL | Neither PR nor PD |
| Neutrophils (ANC) | > 1.5 x 10⁹/L | Any value (treatment-related) | >1.5 OR ≥50% increase from baseline | Not a PD criterion by itself | Not required |
| Bone Marrow | Normocellular, <30% lymphocytes, no nodules | Same as CR (but counts incomplete) | Not required (may show residual CLL) | New or increased CLL infiltrate | Not defined |
| Constitutional Symptoms | None (resolution of all pre-treatment symptoms) | None | None | New onset or worsening | Not defined |
Nodular Partial Response (nPR) - Special Category
nPR is assigned when the patient meets all criteria for PR (≥50% lymph node reduction, spleen/liver no longer palpable, blood counts improved) but the bone marrow biopsy shows persistent lymphoid nodules (aggregates) without diffuse CLL infiltration. The marrow is NOT normocellular (may be hypercellular or hypocellular due to treatment) and lymphocyte percentage may be >30% but as discrete nodules rather than diffuse sheets. nPR was more common in the chemo-immunotherapy era (especially after FCR) and is now rare with targeted agents. Prognosis: nPR is intermediate between PR (worse) and CR (better), but patients with nPR often convert to CR over time (6-12 months) as nodules regress. No change in management is required for nPR; continue therapy as planned, reassess in 3-6 months.
Treatment Emergent Lymphocytosis (TEL) - Not PD
TREATMENT EMERGENT LYMPHOCYTOSIS (TEL) IS NOT PROGRESSIVE DISEASE. BTK inhibitors (ibrutinib, acalabrutinib, zanubrutinib) and PI3K inhibitors (idelalisib, duvelisib, umbralisib) cause rapid redistribution of CLL cells from lymph nodes and spleen into peripheral blood, resulting in an isolated increase in absolute lymphocyte count (ALC) during the first weeks to months of therapy. This is a pharmacodynamic effect, not treatment failure. Management: (1) Do NOT stop or change therapy, (2) Continue treatment, (3) Lymphocytosis typically resolves within 3-6 months (median 2-8 months for ibrutinib, 4-12 months for PI3Ki), (4) Duration of lymphocytosis correlates with depth of nodal response (slow mobilizers may have prolonged TEL up to 12 months), (5) TEL does NOT predict shorter PFS (ibrutinib trials: PFS same for TEL+ vs TEL- patients at 12 months), (6) Do NOT perform lymphocytosis for PD during first 6 months of BTKi therapy UNLESS accompanied by other PD criteria (new nodal enlargement, organomegaly, worsening cytopenias, systemic symptoms). After 6 months, new or increasing lymphocytosis WITHOUT other signs may still be TEL but warrants closer monitoring (repeat assessment in 4-8 weeks). If lymphocytosis persists >12 months or increases with concurrent nodal progression, then PD is diagnosed.
Assessment Logistics & Timing
Timing of Response Assessment by Treatment Type
| Treatment Class | Initial Response Assessment | Confirmed CR Assessment | Response Monitoring Interval | Special Considerations |
|---|---|---|---|---|
| Chemo-immunotherapy (FCR, BR, chlorambucil-obinutuzumab, VR-CAP) | 6-8 weeks after last cycle (end of treatment, EOT) | Confirmed CR requires repeat bone marrow biopsy 2-3 months after initial CR (confirms durable clearance, excludes late nodular regeneration) | Every 3 months for first 2 years, then every 6 months until progression (up to 5 years) | MRD assessment at EOT (bone marrow aspirate flow cytometry, sensitivity 10⁻⁴) predicts PFS; uMRD correlates with 5-year PFS >70% vs 25% for MRD+ |
| Continuous targeted agents (BTKi: ibrutinib, acalabrutinib, zanubrutinib; PI3Ki: idelalisib, duvelisib, umbralisib) | First formal response assessment at 6 months (earlier if rapid PD suspected, e.g., Richter transformation). Interim assessments (3 months, 4 months) optional but not required for ORR endpoint | CR is rare with BTKi alone (5-10%); most respond with PR or SD. Confirmatory bone marrow not routinely required unless considering treatment discontinuation or switch | Every 3-6 months (clinical practice) or per trial protocol (usually every 3 months for first year, then every 6 months). CT imaging: at 6 months, then annually | Treatment emergent lymphocytosis (TEL) common in first 6 months; do NOT misdiagnose as PD. CR may take 12-24 months to achieve; marrow can be deferred until deep clinical response. ALC may never normalize (peripheral CLL may persist without progressive disease) |
| Fixed-duration targeted therapy (venetoclax + obinutuzumab, ibrutinib + venetoclax, venetoclax + rituximab, zanubrutinib + venetoclax, acalabrutinib + venetoclax) | End of treatment (EOT) at completion of fixed cycles (e.g., 12 cycles venetoclax + 6 cycles obinutuzumab → EOT at 12 months). For ibrutinib-venetoclax: 15 cycles (ibrutinib lead-in 3 cycles, then 12 cycles combination) | CR confirmation: Repeat CT and bone marrow biopsy 2-3 months after EOT if initial CR suspected (WATCH & WAIT approach: some converters from PR to CR after stopping treatment due to continued immune clearance) | After EOT: every 3 months for first year, then every 3-6 months for next 2 years, then annually. MRD assessment at EOT and 3-6 months post-EOT | MRD negativity (uMRD4, <10⁻⁴ by flow cytometry or clonoSEQ) strongly predicts durable response (PFS >90% at 2 years in venetoclax-obinutuzumab trials). MRD-guided treatment extension studied in clinical trials (ongoing) |
CT Imaging Requirements and Response Calculation
CONTRAST-ENHANCED CT OF CHEST, ABDOMEN, AND PELVIS IS MANDATORY FOR CR AND PR (iwCLL 2018, same as 2008). Non-contrast CT is insufficient because mesenteric, retroperitoneal, and mediastinal nodes may be indistinct from vessels without contrast. Measure up to 6 of the largest measurable lymph nodes (≥1.5 cm in longest diameter, preferably from different anatomic regions: cervical, axillary, inguinal, mediastinal, retroperitoneal, mesenteric, iliac). For each node, calculate PRODUCT of longest diameter and perpendicular diameter (e.g., 3.2 cm × 2.1 cm = 6.72 cm²). Sum products across all 6 nodes = SUM OF PRODUCTS (SPD). Baseline SPD calculated before treatment initiation. Response thresholds: CR = no node >1.5 cm (regardless of baseline size). PR = ≥50% decrease in SPD from baseline, with no new nodes and no individual node increasing by >1.5 cm from nadir. PD = ≥50% increase in SPD from NADIR (lowest value on treatment), OR any new node >1.5 cm, OR any previously enlarged node increasing by >1.5 cm from nadir. CLL lymph nodes are typically round/oval, soft tissue density, no central necrosis (unless Richter transformation). CT should be performed on the same scanner with same protocol for longitudinal comparability. REPORTING: Include SPD at baseline, nadir, and current assessment. Percentage change calculated as (current SPD - baseline SPD)/baseline SPD × 100%.
Bone Marrow Biopsy for CR Confirmation
CR requires BILATERAL bone marrow aspirate and biopsy (single site acceptable if bilateral not feasible, e.g., patient refusal, technical difficulty, bilateral hip prostheses). Aspirate for morphology and flow cytometry (MRD); biopsy for architecture and cellularity.
CR marrow criteria: (1) Normocellular for age (adults: 30-70% cellularity; elderly: 30-60%; children: 70-100% - not applicable), (2) <30% lymphocytes of all nucleated cells (including both CLL and normal B/T cells), (3) NO lymphoid nodules (any size) - even a single small nodule excludes CR and defines nPR (nodular partial response) instead. Diffuse or paratrabecular infiltration also excludes CR.
If bilateral aspirate and biopsy show discordant results (e.g., one side CR, other side nPR or PR), the WORST result determines response (e.g., CR + nPR = nPR; CR + PR = PR). Exception: if one side shows CR and other side is technical failure (insufficient material, dry tap), the adequate side determines response but document as "CR (single adequate biopsy, contralateral failed" ).
CRi (CR with incomplete blood count recovery) is assigned when marrow meets CR criteria (normocellular, <30% lymphocytes, no nodules) but peripheral blood counts have not recovered (PLT <100 x 10⁹/L and/or Hgb <110 g/L, Hgb in g/L: multiply g/dL by 10) and the cytopenias are attributed to treatment (not CLL). CRi patients are still considered responders for trials, but their prognosis is slightly worse than full CR (similar to PR) in the chemo-immunotherapy era. In targeted therapy era, CRi is uncommon (less myelosuppression).
Minimal Residual Disease (MRD)
MRD Assessment - 2018 Update
The 2018 iwCLL guidelines formally incorporated minimal residual disease (MRD) assessment into response criteria for the first time, acknowledging its strong prognostic value, particularly with venetoclax-based and fixed-duration regimens. MRD refers to CLL cells detected in blood or bone marrow after therapy that are below the detection threshold of conventional morphology (<5% lymphocytes). Standard MRD assay: multiparametric flow cytometry (EuroFlow or 8-color panel with CD19, CD5, CD20, CD79b, CD43, CD81, CD200, and surface light chain restriction). Sensitivity threshold: detection of 1 CLL cell among 10,000 leukocytes (10⁻⁴, 0.01%). Limit of quantification (LOQ) is typically 10⁻⁴; limit of blank (LOB) is 10⁻⁵ but rarely used clinically. MRD negativity (uMRD, "undetectable MRD") is defined as <1 CLL cell per 10,000 leukocytes. Deeper MRD thresholds (10⁻⁵, 10⁻⁶) assessed by clonoSEQ (next-generation sequencing of immunoglobulin heavy chain gene rearrangements) are research tools, not standard practice.
MRD Response Categories
| MRD Category | Definition (per iwCLL 2018) | Sample Source | Clinical Significance (Based on Trials) |
|---|---|---|---|
| MRD-negative (uMRD4, standard) | < 1 CLL cell per 10,000 leukocytes (<10⁻⁴, 0.01%) by flow cytometry (EuroFlow or equivalent, 8+ markers) | Peripheral blood (preferred for monitoring) OR bone marrow (more sensitive, more invasive, required for trial confirmation) | Predicts superior PFS and OS: CLL14 trial (venetoclax-obinutuzumab) uMRD at end of treatment: 3-year PFS 85% vs 35% for MRD+ (HR 0.19, p<0.001). MURANO trial (venetoclax-rituximab): uMRD at 9 months predicts 4-year PFS 83% vs 20% (HR 0.15) |
| MRD-positive (MRD+, MRD detectable) | ≥ 1 CLL cell per 10,000 leukocytes (≥10⁻⁴, ≥0.01%) | Peripheral blood or bone marrow | Higher risk of progression, shorter PFS. However, many MRD+ patients still have durable remissions (especially with continuous BTKi). In CLL14, MRD+ patients still had 3-year PFS 35% (not zero). May convert to MRD-negative over time (slow clearance, especially with BTKi) |
| MRD-low positive (research category, not in iwCLL 2018) | 10⁻⁴ to 10⁻⁵ (1-0.1 CLL cells per 10,000, borderline) | Peripheral blood or bone marrow - confirmed by clonoSEQ | Higher risk than uMRD but lower risk than high-level MRD (>10⁻⁴). May need closer monitoring (every 3 months). MRD-guided treatment extension studied in trials |
| MRD-high positive (>10⁻³, >0.1%) | ≥ 10 CLL cells per 10,000 leukocytes (≥0.1%, 10⁻³) | Peripheral blood or bone marrow | High risk of early progression (median PFS 12-18 months). Consider treatment intensification, change of class, or clinical trial |
MRD Assessment Timing and Clinical Use
| Clinical Scenario | Recommended MRD Assessment Timing | Action if uMRD | Action if MRD+ |
|---|---|---|---|
| Fixed-duration venetoclax + obinutuzumab (CLL14 regimen, 12 months total) | At end of treatment (EOT, 12 months) + 3 months post-EOT (confirms durable clearance, eliminates false positives from treatment effect) | Continue observation. Monitor q3-6 months. No maintenance therapy needed in CLL14 study (uMRD at EOT had 3-year PFS >85%). Role of MRD-triggered retreatment (e.g., re-start venetoclax if MRD reappears) is investigational (ongoing trials: REVIVE, CLL15, MAJIC). | If MRD+ but clinical CR (nodes normal, counts normal, no symptoms), continue observation (many remain PFS >2-3 years). If MRD+ with PR, consider observation OR clinical trial (MRD-guided retreatment, consolidation, switch to BTKi, addition of BTKi to venetoclax). If MRD+ with PD (nodes growing, cytopenias), treat next-line (BTKi). |
| Fixed-duration ibrutinib + venetoclax (Glow/FIXED regimen, 15 cycles: 3 months ibrutinib lead-in, 12 months combination) | At end of combination (EOT, 15 months) + 3-6 months post-EOT (to confirm durability; Glow trial: uMRD rate 56% at EOT, 56% at 3 months post-EOT, durable) | Observation. No maintenance in Glow/FIXED trials; 2-year PFS >95% for uMRD patients. If uMRD persists at 3-6 months post-EOT, excellent prognosis. | Consider observation if clinical CR (Glow trial MRD+ patients still had 2-year PFS 80%). Option: extend venetoclax for additional 6-12 months (off-label, not FDA approved). Switch to BTKi monotherapy if patient is MRD+ and experiencing side effects from venetoclax (diarrhea, neutropenia). |
| Continuous BTKi monotherapy (ibrutinib, acalabrutinib, zanubrutinib) | Not routinely recommended for clinical practice. For trials: optional at 12 months, 24 months, and at end of treatment (if treatment stopped, e.g., due to toxicity) | If uMRD on BTKi (rare, 5-10% after 2-5 years of therapy), consider clinical trial of treatment discontinuation (e.g., iwCLL 2019 stop criteria: uMRD in blood and marrow after 2+ years on BTKi, can stop with close monitoring, PFS >80% at 2 years in some series). NOT routinely recommended outside trials. | Continue BTKi. MRD status does NOT guide therapy for BTKi (PFS excellent even if MRD+, 5-year PFS >70% for first-line ibrutinib). Do NOT change therapy based on MRD alone. |
| Post-allogeneic stem cell transplant (allo-SCT) | At day +100, +180, +365, and annually thereafter (or if GVHD or immunosuppression changes) | uMRD at day +100 predicts 5-year PFS >80% and low relapse risk (10-15%). Consider immunosuppression taper (if no GVHD) to enhance graft-versus-leukemia effect (some patients convert from MRD+ to uMRD after taper). | MRD+ at day +100: CD5+CD19+ cells detected. Risk of relapse ~60% within 2 years. Consider: (1) Donor lymphocyte infusion (DLI, if no active GVHD), (2) Immunosuppression taper, (3) Preemptive venetoclax or BTKi (clinical trials), (4) Azacitidine + DLI (trials). Do NOT wait for clinical relapse (median time from MRD+ to relapse 6-12 months). |
MRD Assay Comparison
| Assay | Sensitivity (Limit of Detection) | Sample Required | Turnaround Time | Cost (USD) | Availability | Advantages | Disadvantages |
|---|---|---|---|---|---|---|---|
| Multiparametric Flow Cytometry (EuroFlow, 8-10 colors) | 10⁻⁴ to 10⁻⁵ (0.01-0.001%) - typically 10⁻⁴ clinical | Fresh peripheral blood (EDTA tube) OR bone marrow aspirate (2-3 mL in heparin), stable 24-48 hours | 1-3 days (local flow lab) to 5-7 days (reference lab) | $150-300 | Widely available (academic centers, large community hospitals with flow cytometry) | Standardized, validated, reproducible, relatively inexpensive, rapid turnaround, can be performed locally, distinguishes CLL from normal B cells (aberrant phenotype: CD5+CD19+, dim CD20, dim CD79b, bright CD43, bright CD200) | Requires specialized flow cytometry expertise, sensitivity limited to 10⁻⁴ (cannot detect very low level disease), may miss CLL with atypical phenotype (rare, 5% of cases), requires fresh sample (not frozen, not old blood >48h) |
| clonoSEQ (Adaptive Biotechnologies, NGS of IgH V(D)J rearrangements) | 10⁻⁶ (0.0001%) - 100x more sensitive than flow | Peripheral blood (2mL in EDTA) or bone marrow aspirate (2mL) can be FROZEN (stable months to years) | 7-14 days (send to central lab, Adaptive Biotechnologies, Seattle, WA) | $500-800 per sample (but requires $2000-3000 baseline sequencing for clonotype identification) | Limited to CLIA-certified reference labs (Adaptive Biotechnologies) - available in US, Europe, Japan, Australia | Most sensitive clinically available assay, can monitor MRD at 10⁻⁶, can be performed on frozen samples (archived biorepositories), independent of phenotype (captures all CLL regardless of marker expression), can track subclones with different IgH rearrangements | Expensive, long turnaround, requires baseline tumor sequencing (clonotype identification, $2000-3000 additional), not real-time, may miss CLL if IgH rearrangement not captured (rare, <2% of CLL with bi-allelic rearrangement), cannot distinguish CLL from normal B cells with same rearrangement (extremely rare) |
| PCR for IgH (clonal rearrangement, patient-specific primers) | 10⁻⁴ to 10⁻⁵ (0.01-0.001%) - similar to flow | Peripheral blood or bone marrow, frozen or fresh | 3-5 days (local molecular lab) | $200-400 | Limited to academic centers with molecular diagnostics | Inexpensive (once primers developed), can be performed locally, moderate sensitivity | Requires baseline clonality testing and patient-specific primer design ($500-1000 additional, 2-4 weeks lead time before monitoring), not standardized across labs (high inter-lab variability), labor intensive, replaced by clonoSEQ |
| Digital droplet PCR (ddPCR, research only) | 10⁻⁵ to 10⁻⁶ (0.001-0.0001%) | Peripheral blood or bone marrow | 2-3 days | $100-200 (research pricing) | Research use only (not CLIA certified for clinical decision making) | Lower cost than clonoSEQ, excellent sensitivity, absolute quantification (no standard curve needed) | Not FDA approved, not standardized, limited availability |
Progressive Disease (PD) & Richter Transformation
iwCLL 2018 Criteria for Progressive Disease (Any ONE of the following)
Lymphadenopathy: ≥ 50% increase in SPD of up to 6 nodes from NADIR (lowest value on treatment) OR any new node >1.5 cm in longest diameter (in any location, including mesenteric, retroperitoneal, mediastinal, cervical, axillary, inguinal, iliac) OR any previously enlarged node increasing by >1.5 cm from nadir. Confirmation: repeat CT scan in 4-8 weeks to confirm progressive growth (unless clinically obvious, e.g., rapidly enlarging painful nodes, obstructive symptoms, or Richter transformation suspected).
Hepatomegaly or Splenomegaly: ≥ 50% increase in palpable enlargement from baseline (e.g., spleen from 4 cm to >6 cm below costal margin) OR new palpable hepatomegaly or splenomegaly that was previously absent (confirmed by CT if palpable exam equivocal due to obesity or body habitus).
Peripheral Blood Lymphocytes: ≥ 50% increase in absolute lymphocyte count (ALC) from baseline (nadir) to >5 x 10⁹/L. EXCEPTION: Treatment emergent lymphocytosis (TEL) in first 6 months of BTK inhibitor or PI3K inhibitor therapy is NOT PD (see separate section). After 6 months, new or increasing lymphocytosis without other signs may still be TEL but warrants close monitoring. Confirmation: repeat CBC in 4-8 weeks.
Cytopenias (attributed to CLL, not treatment toxicity): Decrease in platelet count by ≥ 50% from baseline (nadir) to <100 x 10⁹/L OR decrease in hemoglobin by ≥ 20 g/L (2 g/dL) from baseline (nadir) to <110 g/L (11 g/dL). Must be attributed to CLL progression (bone marrow infiltration increasing) NOT drug-induced myelosuppression (check marrow, reticulocyte count, iron studies, B12/folate, DAT to rule out immune cytopenias).
Constitutional Symptoms (B-symptoms): New onset or worsening of unexplained fever >38.0°C (100.4°F) for ≥14 days without infection, drenching night sweats requiring bedding change, unintentional weight loss >10% of body weight in 6 months, debilitating fatigue (ECOG PS increase by ≥2 points from baseline).
Richter Transformation (see detailed section below): Biopsy-proven transformation to diffuse large B-cell lymphoma (DLBCL), Hodgkin lymphoma (rare, <1% of Richter), or prolymphocytic leukemia (PLL). Clinical suspicion: Rapidly enlarging lymph nodes (doubling in size in <3 months), extranodal disease (bone, central nervous system, kidney, lung, skin, testis), new B-symptoms (fever, drenching sweats, weight loss), elevated LDH (>2x ULN) and/or hypercalcemia. PET-CT: SUVmax >5-10 suggestive (but not diagnostic); biopsy mandatory.
Richter Transformation (RT) - Detailed Management
Richter transformation (RT) occurs in 2-10% of CLL patients, usually from CLL transformation to diffuse large B-cell lymphoma (DLBCL, 90-95% of RT) or Hodgkin lymphoma (5-10%). Median time to RT from CLL diagnosis: 2-5 years. Risk factors: Unmutated IGHV, NOTCH1 mutation (increases risk 5-10x), CD38 and ZAP-70 positivity, complex karyotype, del(17p)/TP53 mutation, prior treatment with purine analogues (fludarabine) or bendamustine. Clinical presentation: Rapidly progressive localized or generalized lymphadenopathy (nodes often >5 cm, painful, may be matted), extranodal involvement (CNS, bone, lung, kidney, testis, skin, GI tract) - uncommon in CLL without RT, B-symptoms (fever, drenching night sweats, weight loss), elevated LDH (>2x ULN, often >1000 IU/L), hypercalcemia (rare in CLL, suggests RT), new cytopenias (anemia, thrombocytopenia). DIAGNOSIS: Biopsy of the most PET-avid node (excisional or core needle; fine needle aspiration INSUFFICIENT). PET-CT: SUVmax >5-10 has 90% sensitivity, 80% specificity for RT (but false positives occur with infection, transformation to high-grade lymphoma or infection). Other findings: Extranodal PET avidity (e.g., bone, liver, spleen SUV >10) highly suggestive. Clonal relationship: Determine if RT is clonally related (same IGHV rearrangement as CLL, 80% of cases, worse prognosis, median OS 6-12 months) or clonally unrelated (distinct lymphoma, 20%, better prognosis, median OS 30-60 months). Treatment: Clonally related DLBCL-type RT: Intensive R-CHOP-like regimens (dose-adjusted EPOCH-R), often followed by allogeneic stem cell transplant (allo-SCT) if chemosensitive (otherwise median OS <6 months). Checkpoint inhibitors (pembrolizumab, nivolumab) if PD-1/PD-L1 expression (20-40% response). Targeted agents: BTKi (ibrutinib) poorly active in RT; venetoclax may have modest activity (10-20% ORR). Clonally unrelated DLBCL-type: Treat as de novo DLBCL (R-CHOP x6 cycles), better outcomes (5-year OS 40-60%). Hodgkin lymphoma-type RT: Treat as Hodgkin lymphoma (ABVD, AVD, or brentuximab vedotin + AVD), 5-year OS 50-70%. Palliation: RT if localized and poor performance status.
Clinical Trial Endpoints
iwCLL 2018 Endpoint Definitions for Clinical Trials
| Endpoint | Definition | Measurement Method | Regulatory Use (FDA/EMA) | Typical Values in Trials (First-line) |
|---|---|---|---|---|
| Overall Response Rate (ORR) | Proportion of patients who achieve CR, CRi, or PR at any time point (best response). SD and PD are non-responders. | CT imaging + physical exam + labs + bone marrow (for CR). Assessed at protocol-defined time points (usually 6 months, then EOT). | Primary endpoint for single-arm registration trials (e.g., ibrutinib approval in relapsed/refractory CLL, ORR 70-85%). Used for accelerated approval (FDA, 2014-2016). | Chemo-immunotherapy (FCR): ORR 80-95%, CR 40-70%. BTKi (first-line): ORR 85-95%, CR 5-15% (low due to persistent peripheral CLL). Venetoclax + obinutuzumab (CLL14): ORR 85%, CR 50%, uMRD 76%. Ibrutinib + venetoclax (Glow): ORR 95%, CR 55%, uMRD 56%. |
| Complete Response Rate (CR rate) | Proportion of patients achieving CR (or CRi) with full recovery of blood counts, normal CT, negative marrow (<30% lymphocytes, no nodules). | Requires confirmatory bone marrow biopsy within 2-3 months of initial CR assessment (to rule out nodular regeneration). CT confirms all nodes <1.5 cm. | Secondary endpoint, but regulatory agencies prefer CR over PR (durable). Used for full approval (e.g., venetoclax for 17p deletion based on CR rate 20%). | FCR: CR rate 40-70% (age-dependent). BR: CR rate 20-30%. Ibrutinib: CR rate 5-10% (but very low). Acalabrutinib: CR rate 5-10%. Zanubrutinib: CR rate 10-15%. Venetoclax alone: CR 20-30%. Venetoclax + rituximab (MURANO, R/R): CR 27-37%. Venetoclax + obinutuzumab: CR 50%. Ibrutinib + venetoclax: CR 55-65%. |
| Progression-Free Survival (PFS) | Time from randomization (or treatment start, for single-arm) to first documented PD (iwCLL 2018 criteria) or death from any cause. | Censored at last follow-up if alive without PD. Kaplan-Meier method. | Primary endpoint for randomized phase 3 trials (e.g., RESONATE-2, CLL14, ELEVATE-TN, ALPINE, GLOW). Preferred by FDA/EMA for full approval. | FCR: median PFS 5-7 years (favorable genetics), 2-3 years (unfavorable). BR: median PFS 2-5 years. Ibrutinib: 5-year PFS 70-80% (first-line). Acalabrutinib: 4-year PFS 80-85%. Zanubrutinib: ALPINE trial 2-year PFS 84% (R/R). Venetoclax + obinutuzumab: CLL14 4-year PFS 74% (uMRD 4-year PFS 85-90%). Ibrutinib + venetoclax: Glow 30-month PFS 88%. |
| Time to Next Treatment (TTNT) | Time from randomization/start of therapy to start of next-line CLL therapy (any reason). | Captured in medical records. Useful for real-world studies. | Secondary endpoint, increasingly used in real-world evidence (RWE) submissions to FDA. | Varies widely by therapy and line of therapy. TTNT not well-standardized across studies. Typically 2-5 years longer than PFS (since patients may have asymptomatic PD not requiring treatment). |
| Duration of Response (DOR) | Time from first documented CR or PR to PD or death (censored at last follow-up if no PD). | Assessed in responders only (CR+PR). | Secondary endpoint, supportive of ORR. | FCR: median DOR 4-6 years (first-line). Ibrutinib: median DOR not reached at 5-7 years (80% still responding). Venetoclax + obinutuzumab: median DOR 4-5 years (first-line). |
| Event-Free Survival (EFS) | Time from randomization to PD, death, or discontinuation for any reason (including toxicity, patient withdrawal, non-compliance). Broader than PFS, captures treatment tolerability. | Intention-to-treat (ITT) population. More stringent than PFS. | Used in some trials (e.g., CLL11, REACH) but less common than PFS. | FCR: median EFS 4-5 years. BR: median EFS 3-4 years. Ibrutinib: 5-year EFS 65-75%. |
| Overall Survival (OS) | Time from randomization to death from any cause. | Censored at last follow-up if alive. Kaplan-Meier method. | Gold standard endpoint for regulatory approval. Rarely used for CLL trials now because effective salvage therapies prolong OS even after PD (cross-over, subsequent lines). | FCR: 10-year OS 60% (favorable genetics), 30% (unfavorable). Ibrutinib: 5-year OS 85-90% (first-line). Venetoclax + obinutuzumab: 4-year OS 85% (first-line). Very high OS rates complicate demonstrating superiority. Often requires 5-10 year follow-up or large sample sizes. |
| Minimal Residual Disease (MRD) Negativity Rate | Proportion of patients achieving uMRD4 (<10⁻⁴ by flow cytometry) in blood and/or bone marrow at specified time points (usually end of treatment, 3-6 months post-treatment). | Multiparametric flow cytometry (EuroFlow, 8-10 colors). Sensitivity 10⁻⁴. | Secondary endpoint (supportive). Increasingly used as surrogate endpoint for PFS in venetoclax-based regimens (FDA qualification requested, not yet granted). | FCR: uMRD4 rate 30-50% (blood) at EOT. BR: uMRD4 10-20%. Ibrutinib: uMRD4 5-10% at 12 months, 15-20% at 24-36 months. Venetoclax + obinutuzumab: 76% uMRD4 at EOT (bone marrow). Ibrutinib + venetoclax: 56% uMRD4 at EOT (bone marrow, Glow trial). |
Clinical Pearls
Critical Pearls for Clinical Practice
TREATMENT EMERGENT LYMPHOCYTOSIS (TEL) is the most common error leading to premature discontinuation of BTKi. Remember: "Lymphocytosis alone, without node enlargement, is NOT progression" in the first 6 months. Educate patients and referring physicians. Continue therapy. Lymphocytosis resolves in median 2-8 months. If still concerned, repeat CT in 4-8 weeks - nodes will be smaller or stable despite high ALC.
Common Pitfalls in Response Assessment
Misdiagnosing treatment emergent lymphocytosis (TEL) as PD in first 6 months of BTKi or PI3Ki → premature treatment discontinuation → loss of response (patients often do NOT re-respond if restarted after drug holiday, due to acquired resistance mutations). Pitfall rate: 20-30% in community practice (surveys). Solution: Education, wait for confirmatory CT (nodes shrink even as ALC rises).
Using non-contrast CT (or no CT) for CR/PR assessment → missing mesenteric/retroperitoneal nodes → overestimating response (calling CR when nodes present but not palpable). Solution: Always order contrast-enhanced CT of chest, abdomen, and pelvis for formal response assessment (baseline, 6 months, EOT, and suspected PD).
Failure to confirm CR with bone marrow biopsy → misclassifying nPR or PR as CR → overestimating CR rate, affecting trial results and patient prognosis (nPR has worse PFS than CR). Solution: Perform bilateral aspirate and biopsy for any patient meeting clinical/radiographic CR criteria, regardless of how "obvious" the response appears.
Calling PD based on isolated lymphocytosis after 6 months of BTKi without CT confirmation → many patients still have TEL for 6-12 months, especially slow mobilizers (older age, female sex, high nodal burden at baseline). Solution: Repeat CBC in 4-8 weeks; if lymphocytosis stable or decreasing, continue therapy. Only call PD if ALC continues increasing (>2x previous value) AND CT shows new/enlarging nodes.
Missing Richter transformation due to reliance on biopsy of wrong node → PET-avid node with SUVmax >10 is most likely to yield diagnosis; biopsy non-avid node (SUVmax <5) often shows CLL only, leading to false reassurance. Solution: Perform core needle or excisional biopsy of the node with highest SUVmax on PET-CT (or largest, fastest-growing node if PET unavailable).
Overinterpreting "stable disease" as response in clinical trials → patients on BTKi may have SD with minimal nodal reduction but excellent PFS (70-80% at 5 years). SD is NOT failure; many patients with SD after 6 months will convert to PR or CR by 12-24 months. Continue therapy, reassess q3-6 months.
Forgetting to measure spleen and liver at every visit → missing progressive organomegaly, which defines PD even if nodes and blood stable. Solution: Document spleen and liver size in cm below costal margin at each physical exam. Use ultrasound or CT if palpable exam difficult (obesity, ascites, post-surgical changes).
The Evidence
iwCLL 2018 - Key Reference
iwCLL guidelines for diagnosis, indications for treatment, response assessment and supportive management of CLL
Hallek M et al. • Blood. 2018;131(25):2745-2760. doi: 10.1182/blood-2017-09-806398. Epub 2018 Apr 9. PMID: 29540348.
Prior iwCLL Guidelines (Historical Context)
Guidelines for the diagnosis and treatment of chronic lymphocytic leukemia: a report from the International Workshop on CLL updating the National Cancer Institute-Working Group 1996 guidelines
Hallek M et al. • Blood. 2008;111(12):5446-5456. doi: 10.1182/blood-2007-06-093906
National Cancer Institute-sponsored Working Group guidelines for chronic lymphocytic leukemia: revised guidelines for diagnosis and treatment
Cheson BD et al. • Blood. 1996;87(12):4990-4997. PMID: 8652811
Landmark Trials Validating CR, PR, and uMRD as Predictors of PFS
Venetoclax and obinutuzumab in patients with CLL and coexisting conditions
Fischer K et al. • New England Journal of Medicine. 2019;380(23):2225-2236. doi: 10.1056/NEJMoa1815281
Fixed-duration ibrutinib-venetoclax in patients with chronic lymphocytic leukemia and comorbidities
Kater AP et al. • NEJM Evidence. 2022;1(7):EVIDoa2200006. doi: 10.1056/EVIDoa2200006
Ibrutinib as initial therapy for elderly patients with chronic lymphocytic leukaemia or small lymphocytic lymphoma: an open-label, multicentre, phase 3 trial
Byrd JC et al. • Lancet Oncology. 2017;18(2):241-250. doi: 10.1016/S1470-2045(16)30671-8
Last Comprehensive Review: 2026