Rabe, Kari G.

Abstract Next‐generation sequencing identified about 60 genes recurrently mutated in chronic lymphocytic leukemia (CLL). We examined the additive prognostic value of the total number of recurrently mutated CLL genes (i.e., tumor mutational load [TML]) or the individually mutated genes beyond the CLL international prognostic index (CLL‐IPI) in newly diagnosed CLL and high‐count monoclonal B‐cell lymphocytosis (HC MBL). We sequenced 59 genes among 557 individuals (112 HC MBL/445 CLL) in a multi‐stage design, to estimate hazard ratios (HR) and 95% confidence intervals (CI) for time‐to‐first treatment (TTT), adjusted for CLL‐IPI and sex. TML was associated with shorter TTT in the discovery and validation cohorts, with a combined estimate of continuous HR = 1.27 (CI:1.17‐1.39, P = 2.6 × 10 −8 ; c ‐statistic = 0.76). When stratified by CLL‐IPI, the association of TML with TTT was stronger and validated within low/intermediate risk (combined HR = 1.54, CI:1.37‐1.72, P = 7.0 × 10 −14 ). Overall, 80% of low/intermediate CLL‐IPI cases with two or more mutated genes progressed to require therapy within 5 years, compared to 24% among those without mutations. TML was also associated with shorter TTT in the HC MBL cohort (HR = 1.53, CI:1.12‐2.07, P = .007; c ‐statistic = 0.71). TML is a strong prognostic factor for TTT independent of CLL‐IPI, especially among low/intermediate CLL‐IPI risk, and a better predictor than any single gene. Mutational screening at early stages may improve risk stratification and better predict TTT.

AbstractMost patients with chronic lymphocytic leukemia (CLL) are diagnosed with early-stage disease and managed with active surveillance. The individual course of patients with early-stage CLL is heterogeneous, and their probability of needing treatment is hardly anticipated at diagnosis. We aimed at developing an international prognostic score to predict time to first treatment (TTFT) in patients with CLL with early, asymptomatic disease (International Prognostic Score for Early-stage CLL [IPS-E]). Individual patient data from 11 international cohorts of patients with early-stage CLL (n = 4933) were analyzed to build and validate the prognostic score. Three covariates were consistently and independently correlated with TTFT: unmutated immunoglobulin heavy variable gene (IGHV), absolute lymphocyte count higher than 15 × 109/L, and presence of palpable lymph nodes. The IPS-E was the sum of the covariates (1 point each), and separated low-risk (score 0), intermediate-risk (score 1), and high-risk (score 2-3) patients showing a distinct TTFT. The score accuracy was validated in 9 cohorts staged by the Binet system and 1 cohort staged by the Rai system. The C-index was 0.74 in the training series and 0.70 in the aggregate of validation series. By meta-analysis of the training and validation cohorts, the 5-year cumulative risk for treatment start was 8.4%, 28.4%, and 61.2% among low-risk, intermediate-risk, and high-risk patients, respectively. The IPS-E is a simple and robust prognostic model that predicts the likelihood of treatment requirement in patients with early-stage CLL. The IPS-E can be useful in clinical management and in the design of early intervention clinical trials.

Abstract To study the impact of dose modification and temporary interruption of ibrutinib in routine clinical practice, we conducted a retrospective study of consecutive CLL patients treated with ibrutinib outside the context of a clinical trial at Mayo Clinic, (Rochester, MN) from 11/2013 to 12/2017. Of 209 patients, 131 (74%) had unmutated IGHV , 38 (20%) had TP53 disruption, and 47 (22%) were previously untreated. A total of 87/209 (42%) patients started reduced dose ibrutinib (<420 mg daily; n = 43, physician preference; n = 33, concomitant medications; and n = 11, other). During 281 person‐years of treatment, 91/209 patients had temporary dose interruption (54%, nonhematologic toxicity; 29%, surgical procedures; 10%, hematologic toxicity; and 7%, other). After a median follow‐up of 24 months, the estimated median event‐free survival (EFS) was 36 months, and median overall survival (OS) was not reached. On multivariable analyses, temporary ibrutinib interruption (hazard ratio [HR]: 2.37, P = .006) and TP53 disruption at ibrutinib initiation (HR: 1.81, P = .048) were associated with shorter EFS, whereas only TP53 disruption (HR: 2.38, P = .015) was associated with shorter OS. Initial ibrutinib dose and dose modification during therapy did not appear to impact EFS or OS. These findings illustrate the challenges associated with continuous oral therapy with ibrutinib in patients with CLL.

7526 Background: Stem cell transplant (SCT) was considered to be beneficial in CLL patients with Richter transformation (RT). We report a single center experience of SCT for RT. Methods: CLL patients with biopsy-confirmed RT to DLBCL who underwent SCT were identified from Mayo Clinic CLL database, and clinical information was abstracted by chart review. Survival analysis was done with the Kaplan-Meier method. Results: Twenty-four of 204 RT patients underwent SCT, 20 autologous and 4 allogeneic. The median lines of prior CLL therapy was 1 (range 0-4). Only 4 patients were exposed to ibrutinib prior to RT. The median age at RT diagnosis was 62 (range 41-73). Five of 17 (29%) patients had bulky disease (≥ 5 cm), 12 of 20 (60%) had elevated LDH, and 6 of 15 (40%) had TP53 disruption (del(17p) or TP53 mutation). The median lines of RT therapy prior to SCT was 2 (range 1-4); treatments included R-CHOP-like alone (n = 7), platinum-based alone (n = 1), both R-CHOP-like and platinum-based (n = 11), novel agents (n = 2), and high dose MTX-based (n = 3). Response prior to SCT was CR in 12 (50%) and PR in 12 (50%) patients. The median time from RT diagnosis to SCT was 6.8 months (range 3.3-42.3). After a median follow-up of 52.7 months after SCT, there were 10 RT relapses, 4 CLL progression, and 11 deaths (7 RT, 1 CLL and 3 unrelated). The median progression-free survival (PFS) was 28.5 months (95% CI 8.3-NA; 1-year PFS 61.8%, 2-year PFS 50.5%). The median post-SCT survival was 56.3 months (95% CI 30.6-76.6; 2-year survival 82.0%, 4-year survival 65.6%). Elevated LDH was associated with worse PFS (median 8.9 months vs NA, P= 0.014) and a trend of worse post-SCT survival (53.7 vs 67.4 months, P= 0.153). Other factors including age, prior CLL treatment (untreated vs treated), bulky disease, response prior to SCT, and TP53 disruption were not associated with PFS or post-SCT survival. Among the 4 allogeneic SCT patients, 1 had RT relapse 10.5 months after SCT and was treated with venetoclax, ibrutinib and obinutuzumab and remained alive at last follow-up (12.9 months after SCT). All 3 other patients remained in remission and alive at last follow up (15.6, 16.1 and 108.5 months after SCT, respectively). Conclusions: SCT may benefit select RT patients. The role of SCT in the novel agent era needs further study.

7525 Background: New prognostic markers in chronic lymphocytic leukemia (CLL) are in demand. Different groups have developed models which combine multiple prognostic markers into a single index to classify CLL patients (pts). The CLL-International Prognostic Index (CLL-IPI) combines five parameters: age, clinical stage, TP53 status, IGHV mutational status, and serum β2 microglobulin levels. B-cell maturation antigen (BCMA) is a cell membrane receptor expressed exclusively on late stage B-cells and plasma cells with elevated serum (s) levels found in B-cell malignancies, such as multiple myeloma (MM). In MM, sBCMA levels can be used to monitor disease status and predict overall survival (OS). To further evaluate this biomarker in other hematologic malignancies, we studied it in CLL. Methods: Untreated (UNTX) CLL pts seen and consented at Mayo Clinic were identified. sBCMA levels were measured on stored sera of 331 UNTX CLL pts using an ELISA-based assay with a polyclonal anti-BCMA antibody from R&D Systems (Minneapolis, MN). The Mann-Whitney analysis was used to assess differences between CLL pts and healthy controls. The relationships between sBCMA and both time to first treatment (TFT) and OS were also assessed using Cox Regression models with an optimal sBCMA cutoff of 40.9 ng/mL. Results: The median age of pts was 61 years, and 71% were male. The distribution of CLL-IPI risk groups was as follows: 135 (41%) Low; 114 (34%) Intermediate; 67 (20%) High; 15 (5%) Very High. The median level of sBCMA in CLL pts (48.6 ng/mL) was higher (P <0.0001) than those of healthy controls (n = 104; 36.03 ng/mL). In CLL pts, sBCMA is significant in univariable analyses of TFT (HR 2.9 (95%CI, 2.0-4.2); P < 0.0001) and OS (HR 2.5 (95%CI, 1.5-4.0); P < 0.0003), and remains significant when adjusting for sex and CLL-IPI factors (HR 2.3 (95%CI, 1.6-3.3), P < 0.0001; HR 1.9 (95%CI 1.1-3.1), P = 0.01, respectively). Conclusions: sBCMA is elevated in CLL pts compared to healthy controls. After adjusting for CLL-IPI and sex, sBCMA levels provided independent prognostic value in predicting TFT and OS in this cohort. Measuring sBCMA with a readily accessible ELISA-based test, provides incremental value over the current CLL-IPI model in predicting prognosis of CLL.

7522 Background: Ibrutinib therapy is associated with an increased risk (~15%) of AF. An accurate risk assessment model for the development of AF in pts starting ibrutinib is not established, and outcomes after AF are not well described. Methods: An IRB approved retrospective review of CLL pts treated with ibrutinib at Mayo Clinic between Oct 2012 and Nov 2018 was conducted. Results: 299 pts were identified with a total of 565 years of ibrutinib exposure (Table). After a median follow-up of 24 months (range 0–70 months), 51 pts developed treatment-emergent AF (13 [25%] CTCAE 3 or higher). Our study assessed 3 clinical prediction models, the Framingham (Schanbel:Lancet 2009), Italian (Visentin:Blood 2018;132:3118), and Shanafelt (Shanafelt:Leuk Lymp; 2017) risk scores. Based on a lower Akaike information criteria, the Italian score was best able to predict risk of treatment emergent AF (2-year risk of AF with score 0 6%; 1-2 8%; 3-4 26%; 5+ 47%). Thirty (61%) pts were treated with medical therapy for AF (27 rate control; 2 rhythm control; 1 both). 16 (31%) pts underwent interventional therapy (3 AV node ablation; 11 cardioversion; and 2 pacemaker). Twelve (23%) pts temporarily held ibrutinib and resumed their original dose, 22 (43%) pts continued reduced dose ibrutinib and 11 (22%) continued their initial ibrutinib dose. Six (12%) pts permanently discontinued ibrutinib. Of 51 pts with treatment-emergent AF, 41 (80%) had a CHA2DS2-VASc score of ≥2 (41% received anticoagulation alone; 12% received antiplatelet therapy alone; 10% received both). No pt developed a thrombotic stroke after treatment-emergent AF. Two major bleeds, (1 GI and 1 intracranial) occurred, one in a pt on concomitant antiplatelet and anticoagulation therapy, and one in a pt receiving neither. The development of AF was associated with shorter event-free survival (HR 2.5, 95%CI 1.5-4.2, p<.001) and shorter overall survival (HR 3.5, 95%CI 2.0-6.3, p<.001). Conclusions: The Italian score was the best predictor of AF development in this cohort of ibrutinib treated pts. Although the vast majority of pts who develop AF after ibrutinib are able to continue therapy, the occurrence of AF appears to be associated with shorter EFS and OS. [Table: see text]

7015 Background: Besides clinical staging, a number of biomarkers predicting OS in CLL have been identified. The multiplicity of markers, limited information on their independent value, and a lack of understanding of how to interpret discordant markers are major barriers to use in routine clinical practice. We developed an integrated prognostic index using the database of the German CLL Study Group (GCLLSG), which was subsequently validated in a cohort of untreated CLL patients (pts) from the Mayo Clinic. Methods: The analysis was based on a dataset collected between 1997 and 2006 in 3 GCLLSG phase III trials. The external validation was performed on a series of newly diagnosed CLL pts managed at Mayo Clinic. Results: The GCLLSG dataset (1,948 physically fit pts at early and advanced stage; median age: 60 yr (range 30-81); median observation time 63.4 mo) was used as a training dataset. 7 parameters were identified as independent predictors for OS: sex, age, ECOG status, del 17p, del 11q, IGHV mutation status, thymidine kinase and β2-microglobulin. By using a weighted grading a prognostic index was derived separating four different pts groups: low risk (score 0 - 2), intermediate risk (score 3-5), high risk (score 6-10) and very high risk (score 11-14) with significant different OS rates (95.2%, 86.9%, 67.7% and 18.7% OS after 5 yr for the low, intermediate, high and very high risk group respectively (p<0.001). This prognostic index was validated in a cohort of 676 newly diagnosed, untreated pts from the Mayo Clinic (median age 61.5 yr (range 32 - 89); median observation time 47.0 mo). The 4 risk groups were reproduced with 98.3%, 95.4%, 75.4% and 10.8% OS after 5 yr. The prognostic index predicts OS independent of Rai/Binet stage and provides accurate estimations regarding time to first treatment (TTF). C-statistic is 0.75. Conclusions: Using a multi-step process including external validation, we developed a comprehensive prognostic index combining clinical, serum, and molecular information into a single risk score for pts with untreated CLL. The prognostic index provides more accurate prediction of both TTF and OS. To our knowledge it is the first prognostic model in CLL to reach the C-statistic threshold (c > 0.70) necessary to have utility at the level of the individual.

6571 Background: Chronic lymphocytic leukemia (CLL) is associated with an increased risk of developing second cancers. However, it is unknown whether CLL alters the natural history of these cancers once they occur. Methods: All patients with breast (n=583,838), colon (n=412,932), prostate (n=632,922), lung (n=489,290), kidney (n=95,902), pancreas (n=82,121) and ovarian (n=61,958) cancer reported to the Surveillance, Epidemiology, and End Results (SEER) Program from 1990 to 2007 were identified. Overall survival (OS; death due to any cause) and cancer-specific survival (death due to cancer site of interest) were examined, comparing patients with or without pre-existing CLL. Age- and sex-adjusted hazard ratios (HRs) were calculated. Results: OS for patients with pre-existing CLL was inferior for patients with breast (HR=1.61; p<0.001), colon (HR=1.65; p<0.001), kidney (HR=1.41; p<0.001), prostate (HR=1.75; p<0.001), and lung (HR=1.22; p<0.001) cancer after adjusting for age and sex. After excluding CLL-related deaths, OS remained shorter among patients with breast (p<0.001), colon (p<0.001), kidney (p=0.03), prostate (p<0.001), and lung (p<0.001) cancer. Cancer-specific survival was inferior for patients with breast (HR=1.29; p=0.03), colon (HR=1.75; p<0.001), and lung cancer (HR=1.17; p<0.001) who had pre-existing CLL after adjusting for age and sex. Conclusions: Several common cancers, including breast, colon, and lung, have inferior overall and cancer-specific survival when there is coexistent CLL. [Table: see text]

4584 Background: PETs (islet cell tumors) are uncommon and often indolent tumors, but little is known about the incidence of PETs in the US and trends in survival. Methods: The SEER registry was used to identify cases of functional PETs (fPETs) and non-functional PETs (nfPETs) diagnosed from 1973–2000. Benign insulinomas were excluded. Incidence rates were age adjusted to the standard US population for 2000. Results: Of 971 patients with PETs, 824 (85%) were nfPETs, 37 (4%) were malignant insulinomas, 88 (9%) were fPETs other than insulinoma, and data were missing for 22 (2%). The crude annual incidence of PETs (per 100,000) for all ages was 0.1 in females and 0.2 in males. The incidence was highest in the age group >70 years (0.4, Table ). Tumors were localized in 109 (11%), regionally advanced in 228 (23%), and distant metastases were present in 545 (56%). Patients with fPETs were younger than patients with nfPETs (mean age 54.2 vs. 57.6, p=0.038) and had a longer median survival (MS) (47 vs. 30 months (mos), p=0.001) but were as likely to have advanced disease (p=0.50). The 5 and 10 year overall survival was 45.3% vs. 32.7% and 31.7% vs. 18.1% for fPETs vs. nfPETs, respectively. MS was 95 mos for localized PETs, 66 mos in regionally advanced PETs and 19 mos for distant metastases (p<0.001). Race did not influence incidence and survival. On multivariate analysis, only age (p<0.0001) and stage (<0.0001) were independently associated with prognosis but the functional status of the tumor approached significance (p=0.053). Survival has improved over time with longer MS in patients diagnosed in later quartiles of the observation period (p<0.001, Table). This difference is not explained by stage migration, as patients in all four quartiles had a similar stage distribution (p=0.79). Conclusions: PETs are uncommon tumors and the prognosis is highly dependent on the stage and the age of the patients. Patients with fPETs may have a better prognosis than nfPETs. Survival has improved over time. [Table: see text] No significant financial relationships to disclose.

Background The CLL international prognostic index (CLL-IPI) is a validated staging system for newly diagnosed CLL patients that combines age, clinical stage, serum Beta-2 microglobulin, TP53, and IGHV mutation status into a single score and stratifies CLL patients into four prognostic risk groups with a c-statistic=0.72. Next-generation sequencing identified ~60 putative driver genes recurrently mutated in CLL, and genome-wide association studies (GWAS) identified 41 single nucleotide polymorphisms (SNPs) associated with CLL risk. We previously showed that a polygenic risk score (PRS) of the weighted average of the number of risk alleles among these 41 SNPs is associated with risk of both CLL and MBL. We and others have also shown that the tumor mutational load (TML), i.e., the total number of somatically mutated driver genes, is associated with time to first treatment (TTT). Herein, we examine whether TML and PRS add prognostic value beyond CLL-IPI for disease progression in a cohort of CLL and high-count MBLs. Methods We used the Mayo Clinic CLL resource to identify newly diagnosed (&lt;2 years) previously untreated CLL and high-count MBL patients based on the 2008 International Workshop CLL (IWCLL) criteria . We extracted DNA from CD5+/CD19+ clonal B-cells and sequenced the coding regions of 59 recurrently mutated CLL driver genes using a custom SureSelect panel and Illumina HiSeq 4000. The median coverage depth per sample was 2737X. Somatic mutations were called using MuTect2 in tumor-only mode. Germline variants were eliminated based on minor allele frequencies &gt;0.01%, and by those identified in 1000 Genomes Project, ExAC and/or ESP6500 databases, unless present in known mutation hotspots or COSMIC. After filtering high/moderate impact mutations, we calculated the TML. Peripheral blood DNA was genotyped on Illumina Omni Express array; after extensive quality control metrics, we calculated the germline PRS as the weighted average of the number of risk alleles among the CLL susceptibility SNPs. Cox regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CI) to test for associations with TTT. We analyzed the low/intermediate risk groups and the high/very high risk groups in stratified analyses and tested for interactions between CLL-IPI and TML or PRS. Survival curves are displayed using the Kaplan-Meier method using P-values from the log-rank test; the PRS is displayed by tertile categories. Results Of 166 patients (120 CLL, 46 MBL), 67% were male and the median age at diagnosis was 62 years (range: 28-85). The median follow-up was 5.3 years, and 73 were treated for progressive disease as defined by the 2018 IWCLL criteria. Low risk CLL-IPI comprised 51%, intermediate risk 27%, high risk 18%, and very-high risk 4%. The most commonly somatically mutated genes were TP53 (8%), CHD2 (8%), BIRC3 (8%), SF3B1 (7%), and NOTCH1 (7%). We found that 42%, 32%, and 26% of patients had 0, 1, or 2+ genes with somatic mutations, respectively. The median PRS was 8.3 (range: 6.1-11.3) which is consistent with our prior PRS study on CLL/MBL and higher than 7.53 found in 7983 controls from our prior work. When we modeled TML, PRS, sex, CLL/MBL status and CLL-IPI together with the joint effects of CLL-IPI with TML and PRS, both interactions were significant in the model (P=0.008 for TML*CLL-IPI and P=0.014 for PRS*CLL-IPI), with c-statistic=0.81 (CI:0.77-0.85). When we stratified by CLL-IPI, TML was associated with shorter TTT in the low/intermediate risk (N=129, continuous HR=2.36 per TML category, CI: 1.61-3.47, P=1.3x10-5, Figure 1.A), but there was no evidence of an association in the high/very-high risk (N=37, continuous HR=1.12 per TML category, CI: 0.70-1. 78, P=0.64, Figure 1.B), after adjusting for PRS, sex, and CLL/MBL status. However, the PRS was associated with a shorter TTT in the high/very-high risk (continuous HR=1.77 per SD, CI: 1.00-3.12, P=0.048, Figure 1.D), with no evidence of an association in the low/intermediate risk (continuous HR=0.95 per SD, CI: 0.95-1.29, P=0.74, Figure 1.C), after adjusting for TML, sex, and CLL/MBL status. Conclusions In our study, TML was prognostic among the low/intermediate CLL-IPI risk groups while the PRS was prognostic among the high/very-high CLL-IPI risk groups. Sequencing CLL driver genes and genotyping relevant germline SNPs at time of diagnosis may provide incremental value over the CLL-IPI in predicting TTT among patients with CLL/MBL. Disclosures Parikh: MorphoSys: Research Funding; Genentech: Honoraria; AbbVie: Honoraria, Research Funding; AstraZeneca: Honoraria, Research Funding; Pharmacyclics: Honoraria, Research Funding; Janssen: Research Funding; Ascentage Pharma: Research Funding; Acerta Pharma: Research Funding. Ding:Merck: Research Funding; DTRM Biopharma: Research Funding. Cerhan:Celgene: Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; NanoString: Research Funding. Kay:MorphoSys: Other: Data Safety Monitoring Board; Infinity Pharmaceuticals: Other: DSMB; Celgene: Other: Data Safety Monitoring Board; Agios: Other: DSMB.