Efficacy of venetoclax in high risk relapsed mantle cell lymphoma (MCL) - outcomes and mutation profile from venetoclax resistant MCL patients.

Venetoclax is effective in relapsed patients with mantle cell lymphoma (MCL). Mechanisms of resistance to venetoclax in MCL are poorly understood. We describe the clinical outcomes and genomic characteristics of 24 multiply relapsed patients (median of five prior lines of therapy) who received venetoclax-based therapies; 67% had progressed on BTK inhibitors (BTKi) and 54% had blastoid or pleomorphic histology. Median follow up after venetoclax treatment was 17 months. The overall response rate was 50% and complete response (CR) rate was 21%, 16 patients had progressed and 15 died. The median progression free, overall and post venetoclax survival were 8, 13.5 and 7.3 months respectively. Whole-exome sequencing (WES) was performed on samples collected from seven patients (including five pairs; before starting venetoclax and after progression on venetoclax). The SMARCA4 and BCL2 alterations were noted only after progression, while TP53, CDKN2A, KMT2D, CELSR3, CCND1, NOTCH2 and ATM were altered 2-4-fold more frequently after progression. In two patients with serial samples, we demonstrated clonal evolution of novel SMARCA4 and KMT2C/D mutations at progression. Mutation dynamics in venetoclax resistant MCL is demonstrated. Our data indicates that venetoclax resistance in MCL is predominantly associated with non-BCL2 gene mutations. Further studies are ongoing in MCL patients to evaluate the efficacy of venetoclax in combination with other agents and understand the biology of venetoclax resistance in MCL.

Genomic profiles and clinical outcomes of de novo blastoid/pleomorphic MCL are distinct from those of transformed MCL.

Blastoid and pleomorphic mantle cell lymphomas (MCLs) are variants of aggressive histology MCL (AH-MCL). AH-MCL can arise de novo (AH-DN) or transform from prior classic variant MCL (AH-t). This study is the first integrated analysis of clinical and genomic characteristics of AH-MCL. Patient characteristics were collected from diagnosis (AH-DN) and at transformation (AH-t). Survival after initial diagnosis (AH-DN) and after transformation (AH-t) was calculated. Regression tree analysis was performed to evaluate prognostic variables and in univariate and multivariate analyses for survival. Whole-exome sequencing was performed in evaluable biopsy specimens. We identified 183 patients with AH-MCL (108 were AH-DN, and 75 were AH-t; 152 were blastoid, and 31 were pleomorphic). Median survival was 33 months (48 and 14 months for AH-DN and AH-t, respectively; P = .001). Factors associated with inferior survival were age (≥72 years), AH-t category, Ki-67 ≥50% and poor performance status. AH-t had a significantly higher degree of aneuploidy compared with AH-DN. Transformed MCL patients exhibited KMT2B mutations. AH-MCL patients with Ki-67 ≥50% had exclusive mutations in CCND1, NOTCH1, TP53, SPEN, SMARCA4, RANBP2, KMT2C, NOTCH2, NOTCH3, and NSD2 compared with low Ki-67 (<50%). AH-t patients have poor outcomes and distinct genomic profile. This is the first study to report that AH-MCL patients with high Ki-67 (≥50%) exhibit a distinct mutation profile and very poor survival.

Low-dose radiation (4 Gy) with/without concurrent chemotherapy is highly effective for relapsed, refractory mantle cell lymphoma.

Mantle cell lymphoma (MCL) generally exhibits an aggressive disease course with poor outcomes. Despite inherent radiosensitivity, radiation therapy (RT) is not commonly used for MCL. This study assesses the role of low-dose RT (LDRT) with concurrent chemotherapy in relapsed, multiply refractory MCL. From 2014 through 2018, 19 patients with relapsed, refractory MCL had 98 sites treated with 4 Gy. Median follow-up from initial LDRT was 15.4 months. Patients had received a median 7 courses of chemotherapy since diagnosis, and 58% were ibrutinib-refractory. Of the 98 sites, 76% were refractory to ongoing chemotherapy, and LDRT was delivered with concurrent chemotherapy for 76%. The complete response (CR) rate was 81% at a median 2.7 months post-LDRT. There were no differences in CR despite ibrutinib-refractory disease, prior chemotherapy courses (>5), or tumor size (>3 cm). There were no RT-related toxicities. Overall survival at 1 year following initial LDRT was 90%, and 1-year progression-free survival following last course was 55%. In summary, LDRT is effective for relapsed, multiply refractory MCL, and may be safely delivered with chemotherapy, to multiple sites, and repeatedly without issue. By treating active sites of disease, LDRT can provide durable local control, help achieve remission, and potentially bridge patients to subsequent novel therapies.