Parikh, Sameer A.

Abstract Introduction: CLL phenotype (CD5+CD23+CD20dim) MBL is present in 5-10% of the general population. The prevalence and outcomes of adults with non-CLL like MBL (including CD5+CD23-, CD5+CD20bright, and CD5-) are not known. We screened for MBL using highly sensitive flow-cytometry in a clinic-based cohort of adults from the Mayo Clinic Biobank. Methods: The Mayo Clinic Biobank is a large scale bio-repository of 50,000 adults seen in primary care-based clinics. Herein, we focused on those adults ≥40 years who had stored peripheral blood mononuclear cells available (10% of the overall cohort). We screened for MBL using an 8 color (CD38, CD45, Kappa, Lambda, CD19, CD23, CD5 and CD20) flow cytometry assay validated to detect clonal B-cell events to the 0.005% level (1/20,000 events). Chi-square tests were used to assess associations with demographic characteristics. Cox regression models were used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI) for death. Results: A total of 2594 adults were screened; their median age was 63 years (range, 40-96) and 1111 (43%) were male. 2445/2594 (94%) individuals had interpretable flow cytometry results. A total of 336 (14%) individuals had MBL identified, of whom 276 (82%) had CLL-like MBL and 60 (18%) had non-CLL like MBL (including 39 adults with CD5- and 21 with CD5+CD23- or CD5+CD20 bright phenotype). A strong association between age and the prevalence of non-CLL like MBL was observed, with 0/278 (0%) in 40-49 years, 6/613 (1%) in 50-59 years, 20/674 (3%) in 60-69 years, 21/490 (4%) in 70-79 years, and 13/114 (11%) ≥80 years demonstrating non-CLL like MBL (p<0.001). Non-CLL like MBL was more common in men compared to women (5% vs. 1%; p<0.001). Compared to adults with no MBL, a higher proportion of non-CLL like MBL had a first-degree relative with a lymphoproliferative disorder (8% vs. 17%; p=0.03), and prior non-hematologic cancer (22% vs. 38%, p=0.006). The remainder of the present analysis is focused on adults with non-CLL like MBL (n=60). After a median follow-up of 5 years (range 0-8 years), 3/60 (5%) adults with non-CLL like MBL developed a hematologic malignancy (one myelodysplastic syndrome, two mantle cell lymphoma) compared to 5/2109 (0.2%) adults with no MBL (two large cell lymphoma, one multiple myeloma, one acute myeloid leukemia, one myelofibrosis). Among adults with non-CLL like MBL, the estimated 7-year overall survival (OS) was 79% compared to 94% in those with no MBL (p<0.001, HR for death 3.8, 95% CI 1.98-7.3). After adjusting for age, sex, and self-reported prior non-hematologic cancer, the HR for death was 1.50 (95% CI 0.74-3.05, p=0.26). Conclusion: In this large study, ~1 of 40 adults seen in a primary care setting had non-CLL like MBL. The prevalence of the non-CLL phenotype MBL increased with age. With current follow-up, the risk of progression to an overt lymphoproliferative neoplasm appears to be low. Citation Format: Sameer A. Parikh, Sara J. Achenbach, Kari G. Chaffee, Neil E. Kay, Connie E. Lesnick, James R. Cerhan, Curtis A. Hanson, Tait D. Shanafelt, Susan L. Slager. The prevalence of non-chronic lymphocytic leukemia (CLL) phenotype monoclonal B-cell lymphocytosis (MBL) in a population-based cohort of U.S. adults [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3256.

Abstract CLL is a highly heritable cancer with first degree relatives of CLL cases having a 7.5-fold increased CLL risk. Genome-wide association studies (GWAS) and linkage studies have been performed to study inherited predisposition; however a larger proportion of heritability to CLL remains unexplained. Rare coding variants might account for the missing heritability information. Inherited loss of function variants in shelterin complex genes (POT1, ACD, TERF1, TINF2, TERF2, TERF2IP- involved in telomere regulation), CDK1 (critical for cell division) and ATM (tumor suppressor gene) have been found to co-segregate in CLL families and be enriched in CLL cases using exome-wide sequencing data. Our study evaluates rare germline variants from these suspect genes segregating in CLL families who are followed at the Mayo Clinic. Using whole exome sequencing (WES), we sequenced 93 CLL families with at least 2 reported CLL cases consisting of 443 individuals: 160 with CLL, 73 with monoclonal B-cell lymphocytosis (MBL), and 210 relatives. DNA was extracted from buccal cells, coding exons were selectively captured using Agilent 50Mb and SureSelect Human All Exon V4 capture kits; sequencing was performed using Illumina HiSeq 2000. Mayo Clinic's DNASeq pipeline uses Novoalign (initial read alignment), Picard (marking duplicate reads), and the Genome Analysis Toolkit (GATK) for local realignment, recalibration, and variant calling. The variant discovery step leverages GATK's HaplotypeCaller in per sample mode and all of the samples across the cohort are jointly genotyped together. All called variants are evaluated with GATK's Variant Quality Score Recalibration tool and annotated for biological relevance (BIOR). Quality control included removing variants that had <75% call rate across the two capture kits, <8x coverage, or phred score<10, resulting in 317,666 remaining variants. Of these, over 80% of the coding sequence had a median read depth of 23 reads. In our pedigrees, we searched for rare variants within the genes described above. We identified suspect variants with the following criteria: 1) enriched in CLL and MBL samples compared to unaffected samples; 2) multiple affected members with the variant within a family; 3) variants present in all sequenced affecteds within the family; 4) rarely seen in an in-house database of non-cancer controls or 1K Genomes; and 5) predicted to have a functional damaging effect (using SIFT). We identified three novel rare missense variants, defined as functionally deleterious, which each co-segregated within a CLL family. Specifically, these variants from shelterin complex genes; POT1 (rs116916706), TERF2IP (rs138458227), and TERF2 (rs749171225), met the criteria. This study further highlights telomere dysregulation as a key process in CLL development. Investigating rare variants within CLL pedigrees with WES can help identify germline variants impacting predisposition to familial CLL. Citation Format: Alyssa I. Clay-Gilmour, Daniel R. O'Brien, Sara J. Achenbach, Celine M. Vachon, Kari G. Chaffee, Timothy G. Call, Jose F. Leis, Aaron D. Norman, Brian F. Kabat, Sameer A. Parikh, Neil E. Kay, Esteban Braggio, James R. Cerhan, Susan L. Slager. Rare germline variants segregating in chronic lymphocytic leukemia (CLL) families [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1226.

SummaryThe effects of ibrutinib on the natural history of autoimmune cytopenias (AIC) among chronic lymphocytic leukaemia (CLL) patients treated in routine clinical practice require further investigation. Using the Mayo Clinical CLL Database, 193 CLL patients treated with ibrutinib between November 2013 and January 2017 outside the context of a clinical trial were identified; complete review of their medical records was performed for details of past history of AIC and treatment‐emergent AIC. We identified 29/193 (15%) patients with history of AIC prior to ibrutinib start. Of 12 patients requiring AIC therapy at ibrutinib start, 8 (67%) were able to discontinue or de‐escalate AIC treatment, and no patient had worsening of their AIC after initiating ibrutinib. Eleven (6%) patients developed treatment‐emergent AIC after a median of 59 (range, 6–319) days following the initiation of ibrutinib, 7 of whom (64%) were able to continue ibrutinib. Overall and event‐free survival from time of ibrutinib start were not significantly different between patients with history of AIC and those with no history of AIC. Treatment‐emergent AIC were seen exclusively in patients with unmutated IGHV and were associated with a shorter EFS. These results suggest a low rate of treatment‐emergent AIC and improvement in patients with existing AIC.

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is a low-grade B-cell neoplasm and ∼2% to 9% patients develop an aggressive lymphoma, most commonly diffuse large B-cell lymphoma (Richter transformation, DLBCL-RT). Programmed death-1 (PD-1) pathway plays a crucial role in tumor host immunity evasion and its blockade has emerged as an effective anti-cancer immunotherapy. PD-L1 and PD-1 expression has shown predictive value in anti-PD cancer immunotherapy; however, it has not been well documented in CLL/SLL and DLBCL-RT. We evaluated PD-1 and PD-L1 expression by immunohistochemistry in 39 CLL/SLL, 15 DLBCL-RT, and 26 other DLBCL. In CLL/SLL, neoplastic B-cell PD-1 expression was weak and restricted to prolymphocytes/paraimmunoblasts within proliferation centers (PCs) and accentuated PCs of all sizes. Neoplastic B-cell PD-1 expression was highly prevalent and demonstrated increased intensity in DLBCL-RT, but in contrast was only rarely seen in other DLBCL (12/15 vs. 1/26; P<0.0001). An excellent correlation (90% concordance) was observed between neoplastic B-cell PD-1 immunohistochemistry positivity and molecularly defined CLL/SLL clonal relatedness in DLBCL-RT. PD-L1 expression was observed on the neoplastic B cells in rare DLBCL-RT and other DLBCL cases (1/15 vs. 1/26; P>0.05) as well as background histiocytes and dendritic cells. Overall survival of DLBCL-RT was significantly inferior to that of the other DLBCL (median, 16.9 vs. 106.1 mo; P=0.002). Our findings suggest a biological continuum from prolymphocytes/paraimmunoblasts in CLL/SLL PCs to the neoplastic B-cells in DLBCL-RT. The characteristic PD-1 expression in DLBCL-RT makes it a potential surrogate marker for determining clonal relatedness to CLL/SLL, which may have important prognostic and therapeutic implications.