Ibrutinib’s role in early-stage chronic lymphocytic leukemia: delayed progression but no survival advantage
Editorial Commentary

Ibrutinib’s role in early-stage chronic lymphocytic leukemia: delayed progression but no survival advantage

Kelly Meza1, Jacqueline C. Barrientos2,3

1Department of Medicine, Baylor College of Medicine, Houston, TX, USA; 2Department of Hematology/Oncology, Mount Sinai Comprehensive Cancer Center, Miami, FL, USA; 3Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Lake Success, NY, USA

Correspondence to: Kelly Meza, MD. Department of Medicine, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX, 77030, USA. Email: kellymezamd@gmail.com.

Comment on: Langerbeins P, Robrecht S, Nieper P, et al. Ibrutinib in Early-Stage Chronic Lymphocytic Leukemia: The Randomized, Placebo- Controlled, Double-Blind, Phase III CLL12 Trial. J Clin Oncol 2025;43:392-402.

Keywords: Ibrutinib; observation; chronic lymphocytic leukemia (CLL)

Received: 28 March 2025; Accepted: 29 July 2025; Published online: 25 September 2025.

doi: 10.21037/actr-25-51

In a recent publication, the German CLL Study Group (GCLLSG) reported on the CLL12 trial, a phase 3, double-blind, placebo-controlled study conducted across 89 sites in Germany. The study focused on patients with early-stage (Binet stage A) chronic lymphocytic leukemia (CLL) who did not meet the criteria for treatment per the International Workshop on CLL guidelines, had an Eastern Cooperative Oncology Group (ECOG) score <3, and a life expectancy of at least 6 months (1). The CLL12 trial aimed to re-evaluate the watch-and-wait strategy for early-stage CLL by assessing the effectiveness of ibrutinib against placebo.

The primary endpoint was event-free survival (EFS), defined as the time from random assignment to active disease progression, initiation of treatment, or death. Secondary endpoints included progression-free survival (PFS), time to next treatment, treatment-free survival, overall survival (OS), best overall response rate, duration of response, and safety.

The trial, conducted between May 2014 and February 2019, participants were randomly assigned to receive either ibrutinib (420 mg daily) or placebo. The GCLLSG score, which includes factors like age, sex, β2-microglobulin levels, ECOG performance status, thymidine kinase (TK) levels, immunoglobulin heavy chain variable region (IGHV) status, and specific deletions, was used to evaluate the risk of disease progression (2). Low-risk patients were placed in a watch-and-wait cohort, while those with intermediate to very high risk were randomized (1:1) to either ibrutinib or placebo, stratified by GCLLSG risk group and TP53 mutation. A total of 363 asymptomatic, treatment-naïve Binet stage A CLL patients at risk of disease progression were enrolled, with 182 assigned to the ibrutinib group and 181 to the placebo group (watch-and-wait). An additional 152 low-risk patients were placed in the watch-and-wait group.

The study, now published in the Journal of Clinical Oncology (1), followed patients for at least 69 months, with a median patient age of 64 years. Several important conclusions can be drawn.

First, the analysis of the primary endpoint showed that ibrutinib significantly delayed progression to symptomatic disease, with 21.4% of patients progressing compared to 51.4% in the placebo group (hazard ratio =0.276, P<0.001). A second key finding was that there was no statistically significant difference in OS between the ibrutinib and placebo groups. The 5-year survival rate was 93.3% in the ibrutinib group and 93.6% in the placebo group (P=0.562). The 10-year survival estimates from CLL diagnosis were 86.5% for the placebo group and 89.8% for the ibrutinib group.

The five-year survival rates were high across all groups: 93.3% in the ibrutinib group, 93.6% in the placebo group, and 97.9% in the watch-and-wait cohort, supporting the watch-and-wait approach as the standard of care for early-stage CLL. The median age in the watch-and-wait group was 57 years. The 5-year EFS rate in this group was 82.1%, and the 5-year time to first treatment (TTFT) rate was 85.7%.

Importantly, the ibrutinib group experienced more frequent cardiovascular toxicities and bleeding events compared to the placebo group. Adverse events, including bleeding and cardiac arrhythmias, occurred more often in the ibrutinib group, and a significant proportion of patients discontinued ibrutinib due to adverse events (44.7% in the ibrutinib group vs. 23.2% in the placebo group).

Several limitations of the CLL12 trial should be carefully considered. First, the relatively short observation period (median of 69.3 months) and the low number of deaths (26 deaths) reduced the statistical power to detect a survival benefit, providing only 25.6% power to identify the predefined survival advantage. Additionally, the high incidence of adverse events, particularly cardiovascular complications, resulted in early treatment discontinuation in 44.7% of patients in the ibrutinib group, compared to 23.2% in the placebo group. This is a critical consideration, as long-term ibrutinib therapy is associated with significant toxicity.

Furthermore, the trial did not specify a first-line treatment for patients who progressed and required intervention, introducing potential confounding factors. The rapidly evolving landscape of CLL treatment makes it challenging to standardize first-line therapy over an extended period, which could influence survival outcomes. Lastly, the study enrolled fewer than 20 patients per group with TP53 aberrant disease, so the outcomes for this high-risk cohort may not be fully represented.

A critical point is the impact of second cancers in the placebo group, which were nearly twice as frequent as in the ibrutinib group. This suggests an altered antitumor response in untreated patients, aligning with findings of T-cell exhaustion in progressing patients and the immunomodulatory effects of ibrutinib on T-cell function. This perceived improvement in immune surveillance, preventing second cancers, came at the expense of higher rate of other toxicities and the need for therapy discontinuation.

Subsequent research reinforced these findings, showing that up to 50% of early-stage CLL patients did not experience disease progression or a decline in quality of life over at least 10 years (3). This led to the current approach, where therapy is delayed until symptoms or disease progression occur, emphasizing that some patients may never require treatment and highlighting the importance of individualized care and careful monitoring in CLL management.

Earlier analyses have demonstrated the superiority of the watch-and-wait approach in terms of PFS. Some controversies still support the watch-and-wait strategy for early-stage CLL. Clinical trials have not shown a survival benefit for chemotherapy in asymptomatic, early-stage CLL patients, reinforcing the watch-and-wait approach (4). The CLL1 trial also highlighted the lack of survival benefit with early chemotherapy in early-stage CLL, supporting the watch-and-wait method (5), which is included in current guidelines, even for high-risk patients (6).

While the CLL12 trial confirms that ibrutinib can delay progression to symptomatic disease in early-stage CLL, it does not provide a survival benefit compared to the watch-and-wait approach (7). Given the high survival rates in both the ibrutinib and placebo groups, along with the significant adverse events associated with continuous ibrutinib therapy, the watch-and-wait strategy remains the gold standard for most early-stage CLL patients.

The concept of “watch-and-wait” in CLL management has been a cornerstone of treatment since the 1980s, particularly for early-stage, asymptomatic patients. Pivotal studies from the UK and France demonstrated that early-stage, asymptomatic CLL patients did not benefit from immediate chemotherapy, such as chlorambucil or cyclophosphamide-based combinations. These treatments were not only ineffective but also caused significant harm, including infections and secondary cancers. As a result, “watch-and-wait” became an important approach for these patients, allowing for more conservative monitoring until disease progression (7-9). Emerging data have raised concerns about the adverse clinical consequences of the “watch-and-wait” strategy, including hypogammaglobulinemia, infections, non-hematological malignancies, and clonal evolution (10-14). These risks highlight the potential need for alternative therapeutic options, especially for high-risk early-stage patients who may benefit from earlier intervention.

The CLL12 trial is significant as it represents a new frontier in CLL therapy, providing evidence for the potential benefits of early treatment. Previous studies on ibrutinib in early-stage CLL were based primarily on a pooled analysis of high-risk patients, including those with TP53 mutations (15). CLL12 suggested that ibrutinib could improve outcomes for high-risk early-stage patients. However, given the high survival rates in both the ibrutinib and placebo groups, along with the significant adverse events associated with continuous ibrutinib therapy, the watch-and-wait strategy remains the gold standard for most early-stage CLL patients. This suggests that, while ibrutinib may offer benefits in certain high-risk populations, the risks of long-term therapy, including serious adverse events, make clinical observation the preferred approach for many early-stage patients. One alternative is acalabrutinib, a second-generation BTKi, being evaluated as an alternative to observation. While it theoretically has fewer side effects than ibrutinib, its efficacy over “watch-and-wait” in early-stage CLL remains unproven, with definitive results still pending from clinical trials (16-18).

Prognostic tools for early-stage CLL have significantly evolved beyond traditional staging systems, aiming to better identify patients at risk for early progression who might benefit from closer monitoring or early intervention trials. The Rai and Binet staging systems, while still widely used due to their clinical simplicity, lack the precision to capture the biological heterogeneity of CLL. As understanding of the disease deepened, additional markers were integrated into prognostic models. Clinical parameters like lymphocyte doubling time (LDT; <12 months), beta-2 microglobulin (B2M >3.5 mg/L), and TK (>7.1 U/L) have been shown to predict shorter TTFT and OS. Genetic factors, including unmutated IGHV, TP53 mutations and/or deletion 17p, and deletion 11q, are now well-established indicators of aggressive disease. Composite scores such as the Chronic Lymphocytic Leukemia International Prognostic Index (CLL-IPI), which incorporates age, clinical stage, B2M, IGHV status, and TP53 disruption, have become standard in prognostication. Similarly, the GCLLSG score includes additional variables like ECOG performance status and TK levels. Other models like MD Anderson Cancer Center (MDACC) and Chronic Lymphocytic Leukemia Prognostic Model (CLL-PM) refine risk prediction by incorporating nodal burden and lactate dehydrogenase (LDH) levels or focusing specifically on early-stage disease. Simpler models like International Prognostic Score for Early-stage CLL (IPS-E) (IGHV status, lymphocyte count >15×109/L, and palpable nodes) offer utility at diagnosis but lack key molecular markers. Meanwhile, emerging tools explore novel parameters such as complex karyotype, CD38, NOTCH1 and SF3B1 mutations, microRNA expression, and immune dysregulation biomarkers. Although these tools effectively stratify patients by risk and aid in clinical trial selection, none have yet justified changing the standard “watch-and-wait” approach, as early intervention trials (e.g., CLL12, EVOLVE, PreVent-ACaLL) have failed to demonstrate OS benefits. As multi-omics approaches like transcriptomics and proteomics gain traction, future models may integrate broader molecular profiles to further refine prognosis in early-stage CLL (19-22).

In addition to single-agent therapies, several combination regimens are being explored in clinical trials. These combinations include venetoclax with obinutuzumab, acalabrutinib and obinutuzumab, acalabrutinib and venetoclax, ibrutinib and pembrolizumab, and lenalidomide for high-risk early-stage CLL patients (18,23-30) (Table 1). While some of these combinations have shown promising efficacy (24), they may also introduce new toxicities that complicate treatment decisions. These side effects can reduce drug tolerability, lead to treatment discontinuation, and potentially cause disease progression, raising significant concerns about patient quality of life and treatment duration (17).

Table 1

Characteristics of clinical trials

Study Trial phase ClinicalTrials.gov Intervention Study population Outcome
EVOLVE (SWOG), Stephens et al., 2021 (28) III NCT04269902 Early intervention with venetoclax and obinutuzumab or delayed therapy with venetoclax and obinutuzumab Adult patients with untreated asymptomatic CLL or SLL OS at 6 years, FACT
High risk CLL-IPI score ≥4
Complex cytogenetics (≥3 cytogenetic abnormalities)
Spain, Abrisqueta et al., 2019 (18) III NCT04178798 Acalabrutinib or observation Adult patients with untreated asymptomatic CLL EFS, PFS, OS, ORR, TTNT
GCLLSG prognostic index with intermediate [3–5], high [6–10] or very high [11–14] risk scores
PreVent-ACaLL, Niemann et al., 2019 (30) II NCT03868722 Acalabrutinib and venetoclax or observation Patients with untreated CLL at high (>65%) risk for infection and/or in need of CLL treatment within 2 y of diagnosis Grade ≥3 infection-free survival at 24 weeks
Moffitt Cancer Center, Chavez et al., 2018 (25) II NCT03514017 Pembrolizumab in combination with ibrutinib High-risk patients with untreated CLL ORR, TTR, PFS
Mayo Clinic, Parikh et al., 2018 (27) II NCT03516617 Acalabrutinib alone or acalabrutinib/obinutuzumab or observation alone Adult patients with untreated asymptomatic CLL or SLL MRD-negative complete response, time to first therapy, ORR, PFS, OS, TTNT
Low-intermediate and high risk and very high risk CLL-IPI score
MDACC, Burger et al., 2017 (23) II NCT03207555 Ibrutinib Adult patients with untreated asymptomatic CLL CR, CRi
Estimated TTFT of ≤3 years, according to MDACC nomogram
OSU, Woyach et al., 2015 (29) II NCT02518555 Ibrutinib concurrently with vaccination (PCV13, trivalent influenza, and DTaP) or sequentially after vaccination Adult patients with CLL/SLL and ≥1 of following high risk genomic features: 2-year PFS, MRD
- FISH del(17p)
- FISH del(11q)
- Complex karyotype (≥3 cytogenetic abnormalities)
- Unmutated IGHV
OSU, Rogers et al., 2023 (24) II NCT01351896 Concurrent lenalidomide and PCV13 or sequential PCV14 and lenalidomide Adult patients with untreated, asymptomatic CLL/SLL and ≥1 high-risk genomic features: OS, PFS, TTNT
- FISH del(17p)
- FISH del(11q)
- Complex karyotype (≥3 cytogenetic abnormalities)
- Unmutated IGHV

CLL, chronic lymphocytic leukemia; CLL-IPI, Chronic Lymphocytic Leukemia International Prognostic Index; CR, complete response; CRi, complete remission with incomplete count recovery; DTaP, diphtheria, tetanus, and pertussis vaccine; EFS, event-free survival; FACT, functional assessment of cancer therapy; FISH, fluorescence in situ hybridization; GCLLSG, German Chronic Lymphocytic Leukemia Study Group; IGHV, immunoglobulin heavy chain variable region; MDACC, MD Anderson Cancer Center; MRD, minimal residual disease; ORR, objective response rate; OS, overall survival; OSU, The Ohio State University; PCV13, pneumococcal conjugate vaccine 13; PCV14, pneumococcal conjugate vaccine 14; PFS, progression-free survival; SLL, small lymphocytic lymphoma; TTFT, time to first therapy; TTNT, time to next treatment; TTR, time to response.

We are entering an era where a range of effective anti-CLL therapies are available, offering reduced toxic effects on bone marrow and immune status compared to older treatments. Coupled with advancements in prognostic tools for disease progression, this progress allows for a reevaluation of early treatment in asymptomatic or minimally symptomatic high-risk patients. Ongoing clinical trials are actively exploring early treatment strategies for both low and high-risk early-stage CLL patients, with the goal of refining the treatment paradigm. These trials have the potential to pave the way for broader adoption of early treatment approaches. However, until their results mature, the “watch-and-wait” strategy will remain the standard for many early-stage patients (6).

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, AME Clinical Trials Review. The article has undergone external peer review.

Peer Review File: Available at https://actr.amegroups.com/article/view/10.21037/actr-25-51/prf

Funding: None.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://actr.amegroups.com/article/view/10.21037/actr-25-51/coif). J.C.B. reports receiving research/grants support from Beigene, Janssen, and Abbvie; consulting fees from Beigene, AstraZeneca, Janssen, and BMS; and has participated on the Data Safety Monitoring Board or Advisory Board of Beigene, AstraZeneca, Janssen, and BMS. The other author has no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

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doi: 10.21037/actr-25-51
Cite this article as: Meza K, Barrientos JC. Ibrutinib’s role in early-stage chronic lymphocytic leukemia: delayed progression but no survival advantage. AME Clin Trials Rev 2026;4:7.

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