Introduction: Mantle cell lymphoma (MCL) is usually an incurable lymphoma with no standard frontline therapy. Increasingly, Bruton tyrosine kinase inhibitors are utilized in frontline therapy, especially in older patients, but data remain limited in younger patients. We report our experience with a cohort of patients with MCL who received frontline second-generation BTKi +/- rituximab.

Methods: We reviewed all patients treated at our institution with either acalabrutinib or zanubrutinib (BTKi) +/- maintenance rituximab who had therapy initiated by July 10, 2024. Adverse events (AEs) were graded based on CTCAE v5. We defined patients as either younger or older: patients <65 years old were considered younger unless noted to be autologous hematopoietic stem cell transplant (ASCT) ineligible. Patients ≥70 years were considered older. Patients aged 65-70 were assessed for ASCT eligibility; ASCT-ineligible patients were considered older. A cohort of patients who had frontline standard-of-care chemotherapy (R-HyperCVAD or R-CHOP/R-DHAP) was also collected for comparison to the younger BTKi-treated cohort.

Results: Thirty patients received frontline second-generation BTKi. Eleven (37%) were younger and 19 (63%) were older. Twenty-three patients (77%) received acalabrutinib (10 with rituximab maintenance) and 7 patients (23%) received zanubrutinib (4 with rituximab maintenance). Twenty (67%) were male, 27 (90%) were white, and 3 (10%) were black. Median age was 70.9 years (range 44.8-93.4). Twenty-five (83%) had ECOG performance status (PS) 0-1. Twenty-seven patients had advanced stage disease (90%). MIPIb was high risk in 21 (70%); Ki-67 was ≥ 50% in 6/26 (23%) and ≥ 30% in 12/26 (46%). Three (10%) patients had blastoid MCL. Five of 26 (19%) patients had a TP53 aberration. Between younger and older cohorts, there were no significant differences in sex, ECOG PS, blastoid MCL, or presence of TP53 aberrations. MIPIb was significantly higher in older patients (6.3 vs. 7.2, p=0.003).

Overall, 24 patients (80%) had an AE related to BTKi, with 7 (23%) experiencing a serious AE (SAE). The most common AEs were bleeding/bruising (33%), infections (n=8, 27%; 1 URI, 4 pneumonia, 1 bacteremia, 1 urinary tract infection, 1 cellulitis; 3 were SAEs), and rash (20.0%). There was no significant difference between rate of any AE or SAE between older and younger patients. Five patients discontinued BTKi due to toxicity (recurrent neutropenia, rash, cellulitis, pneumonitis, dysgeusia) and one due to patient preference.

Thirty-two patients were included in the frontline chemotherapy cohort. Twenty-five patients (78.1%) were male, 29 (90.6%) were white, two (6.3%) were black, and one (3.1%) was Hispanic. Median age was 60.3 years (range 27.3-74.5 years). Twenty-eight (87.5%) patients had an ECOG PS 0-1. Median stage was 4 (range 2-4) and median MIPIb was 6.8 (range 5.4-9.6). Nineteen (59.4%) of patients had classical MCL and 13 (40.6%) had blastoid/pleomorphic MCL. Five of 28 (18%) patients had a TP53 aberration. Comparing younger patients who received frontline BTKi and younger patients who received frontline chemotherapy, there were no significant differences in sex, ECOG PS, MIPIb, or presence of TP53 aberrations or proportion of patients who received maintenance rituximab; however, the younger BTKi cohort did have a significantly lower incidence of blastoid MCL (10% vs. 37%, p=0.02).

Median follow-up for the entire cohort (n=62) was 58 months; estimated 3-year PFS for the BTKi (n=30) and chemotherapy cohorts (n=32) was 57% (95%CI 34-74%) vs. 43% (95%CI 26-60%).

Median follow-up for the younger BTKi and younger chemotherapy cohorts was 35 and 102 months, respectively. Estimated 3-year PFS for the younger BTKi cohort (n=11) vs. younger chemotherapy cohort (n=27) was 52% (95%CI 20-77%) vs. 48% (95%CI 25-61%).

Conclusions: Second-generation BTKi with and without rituximab appear safe and effective frontline therapy for MCL regardless of patient age. We also observed excellent BTKi outcomes in younger patients comparable to standard-of-care chemotherapy. Limitations include a higher proportion of patients in the frontline chemotherapy group with blastoid MCL as well as relatively short follow-up in the BTKi cohort. Nevertheless, second generation BTKi may represent an effective frontline therapeutic approach for patients with MCL. Further studies are needed to determine the role of chemotherapy with BTKi vs chemotherapy-free regimens in this setting.

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2025
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