Frequency of Common and Uncommon BRAF Alterations among Colorectal and Non-Colorectal Gastrointestinal Malignancies

BACKGROUND

The predictive and prognostic role of BRAF alterations has been evaluated in colorectal cancer (CRC); however, BRAF alterations have not been fully characterized in non-CRC gastrointestinal (GI) malignancies. In the present study, we report the frequency and spectrum of BRAF alterations among patients with non-CRC GI malignancies.

METHODS

Patients with CRC and non-CRC GI malignancies who underwent somatic tumor profiling via a tissue-based or liquid-based assay were included in this study. Gain-of-function BRAF alterations were defined as pathogenic/likely pathogenic somatic short variants (SVs), copy number amplifications ≥8, or fusions (RNA or DNA).

RESULTS

Among 51,560 patients with somatic profiling, 40% had CRC and 60% had non-CRC GI malignancies. BRAF GOF alterations were seen more frequently in CRC (8.9%) compared to non-CRC GI malignancies (2.2%) (p < 0.001). Non-CRC GI malignancies with the highest prevalence of BRAF GOF alterations were bile duct cancers (4.1%) and small intestine cancers (4.0%). Among BRAF GOF alterations, class II (28% vs. 6.8%, p < 0.001) and class III (23% vs. 14%, p < 0.001) were more common in non-CRC GI malignancies. Among class II alterations, rates of BRAF amplifications (3.1% vs. 0.3%, p < 0.001) and BRAF fusions (12% vs. 2.2%, p < 0.001) were higher in non-CRC GI malignancies compared to CRC.

CONCLUSIONS

Non-CRC GI malignancies demonstrate a distinct BRAF alteration profile compared to CRC, with a higher frequency of class II and III mutations, and more specifically, a higher incidence of BRAF fusions. Future studies should evaluate clinical implications for the management of non-CRC GI patients with BRAF alterations, especially BRAF fusions.

A soluble LAG-3 protein (eftilagimod alpha) and an anti-PD-L1 antibody (avelumab) tested in a phase I trial: a new combination in immuno-oncology

BACKGROUND

Eftilagimod alpha (efti) is a major histocompatibility complex class II agonist activating antigen-presenting cells which leads to greater systemic type 1 T helper response and more cytotoxic CD8+ T-cell activation. This phase I trial evaluated the administration of efti, a soluble lymphocyte activation gene-3 (LAG-3) protein, combined with the anti-programmed death-ligand 1 (PD-L1) antibody avelumab in advanced solid tumors.

PATIENTS AND METHODS

Patients with heavily pretreated metastatic solid tumors received intravenous avelumab (800 mg) combined with subcutaneously administered efti (6 or 30 mg) for up to 12 cycles, followed by avelumab monotherapy. The primary endpoint was the assessment of the recommended phase II dose (RP2D) of efti in combination with avelumab.

RESULTS

Twelve patients with different tumor entities were enrolled (six patients in each cohort). During treatment, no dose-limiting toxicities occurred, and the severity of most adverse events was grade 1 or 2. In total, nine serious adverse events were documented, resulting in a fatal outcome in two cases, but none of them were assessed to be treatment related. Five patients (42%) achieved partial response. The median progression-free survival was 1.96 months and the median overall survival was not reached, with a 12-month survival rate of 75%.

CONCLUSION

Subcutaneously administered efti plus avelumab was well tolerated, and efti of 30 mg was determined to be RP2D. The activity is promising and warrants further investigation in future phase II trials.

Black Patients with Metastatic Castrate-Resistant Prostate Cancer Have a Shorter Time Interval Between PSA and Clinical Progression on Novel Hormonal Therapies plus Avelumab

BACKGROUND

Black men are at higher risk for prostate cancer death. Previous studies showed a benefit of different therapies, including immune-based therapy, for Black men with metastatic prostate cancer. We sought to explore the efficacy of the PD-L1 inhibitor avelumab in Black men with metastatic castrate-resistant prostate cancer (mCRPC) progressing after abiraterone or enzalutamide.

METHODS

This pilot phase II study enrolled self-identified Black patients who developed mCRPC on next-generation hormonal therapies (NHTs) abiraterone acetate or enzalutamide (NCT03770455). Enrolled patients received avelumab 10mg/kg IV every 2 weeks while remaining on the same NHTs. The primary endpoint of our study was ≥ 50% reduction in prostate specific antigen (PSA) at ≥8 weeks.

RESULTS

A total of eight patients were enrolled. The median duration on NHTs prior to enrollment was 364 days (95% CI, 260.9-467.1). The median time to initiate avelumab was 8 days (3-14). With a median follow-up of 196 days, no patients achieved the primary endpoint. The median time to PSA progression was 35 days (95 CI%, 0-94.8) and the median time to radiographic and/or clinical progression was 44 days (95 CI%, 0-118.5). The study was closed prematurely due to safety concerns related to the rapid clinical progression observed in the patients enrolled on study.

CONCLUSION

In conclusion, the addition of avelumab to NHT did not demonstrate clinical activity in Black men with new mCRPC. The unexpected short interval between PSA and radiographic and/or clinical progression observed in this study has potential clinical implications.ClinicalTrials.gov Identifier: NCT03770455 (IND number 139559).

The impact of genetic aberrations on response to radium-223 treatment for castration-resistant prostate cancer with bone metastases

BACKGROUND

Radium (Ra)-223 is an established treatment option for patients with metastatic castrate-resistant prostate cancer (mCRPC) who have symptomatic bone metastases without soft tissue disease. Studies have indicated genetic aberrations that regulate DNA damage response (DDR) in prostate cancer can increase susceptibility to treatments such as poly ADP-ribose polymerase inhibitors and platinum-based therapies. This study aims to evaluate mCRPC response to Ra-223 stratified by tumor genomics.

METHODS

This is a retrospective study of mCRPC patients who received Ra-223 and genetic testing within the Mayo Clinic database (Arizona, Florida, and Minnesota) and Tulane Cancer Center. Patient demographics, genetic aberrations, treatment responses in terms of alkaline phosphatase (ALP) and prostate-specific antigen (PSA), and survival were assessed. Primary end points were ALP and PSA response. Secondary end points were progression-free survival (PFS) and overall survival (OS) from time of first radium treatment.

RESULTS

One hundred and twenty-seven mCRPC patients treated with Ra-223 had germline and/or somatic genetic sequencing. The median age at time of diagnosis and Ra-223 treatment was 61.0 and 68.6 years, respectively. Seventy-nine (62.2%) had Gleason score ≥ 8 at time of diagnosis. 50.4% received prior docetaxel, and 12.6% received prior cabazitaxel. Notable alterations include TP53 (51.7%), BRCA 1/2 (15.0%), PTEN (13.4%), ATM (11.7%), TMPRSS2-ERG (8.2%), RB deletion (3.4%), and CDK12 (1.9%). There was no significant difference in ALP or PSA response among the different genetic aberrations. Patients with a TMPRSS2-ERG mutation exhibited a trend toward lower OS 15.4 months (95% confidence interval [CI] 10.0-NR) versus 26.8 months (95% CI 20.9-35.1). Patients with an RB deletion had a lower PFS 6.0 months (95% CI 1.28-NR) versus 9.0 months (95% CI 7.3-11.1) and a lower OS 13.9 months (95% CI 5.2-NR) versus 26.5 months (95% CI 19.8-33.8).

CONCLUSIONS

Among mCRPC patients treated with Ra-223 at Mayo Clinic and Tulane Cancer Center, we did not find any clear negative predictors of biochemical response or survival to treatment. TMPRSS2-ERG and RB mutations were associated with a worse OS. Prospective studies and larger sample sizes are needed to determine the impact of genetic aberrations in response to Ra-223.

Comprehensive Genomic Profiling of Cell-Free DNA in Men With Advanced Prostate Cancer: Differences in Genomic Landscape Based on Race

Advanced prostate cancer (aPC) in Black men was reported to present with aggressive features and to be associated with poor prognosis. Herein, we compared the cell-free DNA (cfDNA) genomic landscape of aPC in Black vs White men. Patients (pts) with aPC from 6 academic institutions and available cfDNA comprehensive genomic profiling (CGP) were included. Association between mutated genes and race was evaluated using Barnard’s test and a Probabilistic Graphical Model (PGM) machine learning approach. Analysis included 743 aPC pts (217 Black, 526 White) with available cfDNA CGP. The frequency of alterations in the androgen receptor gene was significantly higher in Black vs White men (55.3% vs 35% respectively, P < .001). Additionally, alterations in EGFR, MYC, FGFR1, and CTNNB1 were present at higher frequencies in Black men. PGM analysis and Barnard’s test were concordant. Findings from the largest cohort of Black men with aPC undergoing cfDNA CGP may guide further drug development in these men.

3D Printed Solutions for Spheroid Engineering and Cancer Research

In multicellular organisms, cells are organized in a 3-dimensional framework and this is essential for organogenesis and tissue morphogenesis. Systems to recapitulate 3D cell growth are therefore vital for understanding development and cancer biology. Cells organized in 3D environments can evolve certain phenotypic traits valuable to physiologically relevant models that cannot be accessed in 2D culture. Cellular spheroids constitute an important aspect of in vitro tumor biology and they are usually prepared using the hanging drop method. Here a 3D printed approach is demonstrated to fabricate bespoke hanging drop devices for the culture of tumor cells. The design attributes of the hanging drop device take into account the need for high-throughput, high efficacy in spheroid formation, and automation. Specifically, in this study, custom-fit, modularized hanging drop devices comprising of inserts (Q-serts) were designed and fabricated using fused filament deposition (FFD). The utility of the Q-serts in the engineering of unicellular and multicellular spheroids-synthetic tumor microenvironment mimics (STEMs)—was established using human (cancer) cells. The culture of spheroids was automated using a pipetting robot and bioprinted using a custom bioink based on carboxylated agarose to simulate a tumor microenvironment (TME). The spheroids were characterized using light microscopy and histology. They showed good morphological and structural integrity and had high viability throughout the entire workflow. The systems and workflow presented here represent a user-focused 3D printing-driven spheroid culture platform which can be reliably reproduced in any research environment and scaled to- and on-demand. The standardization of spheroid preparation, handling, and culture should eliminate user-dependent variables, and have a positive impact on translational research to enable direct comparison of scientific findings.

OUP accepted manuscript

Background

The outcomes of metastatic hormone-sensitive prostate cancer (mHSPC) have significantly improved through treatment intensification, yet Black representation in those studies is suboptimal.

Methods

A multi-institutional, retrospective analysis of Black men with mHSPC was conducted, focusing on baseline demographics, treatment patterns, genomic profiles, clinical outcomes including prostate-specific antigen response, time to castrate-resistant prostate cancer (CRPC), and subsequent treatments.

Results

A total of 107 patients, median age 64 years, 62% with de novo metastases at diagnosis and 64% with high-volume disease, were included. Twenty-nine patients (27%) were treated with androgen deprivation therapy (ADT) with and without first generation anti-androgens, while 20%, 38% and 5% received chemotherapy, abiraterone, and enzalutamide, respectively. At time of data cut-off, 57 (54%) patients had developed CRPC, with a median time to CRPC of 25.4 months (95% CI 20.3-30.4). The median time to CRPC was 46.3 months (18.9-73.7) and 23.4 months (18.6-28.2) for patients who received ADT with or without first-generation anti-androgens and treatment intensification, respectively. The 2-year survival rate was 93.3%, and estimated median overall survival of was 74.9 months (95% CI, 68.7-81.0). Most patients (90%) underwent germline testing; the most frequent known alterations were found within the DNA repair group of genes. Somatic testing revealed pathogenic alterations of interest, notably TP53 (24%) and CDK12 (12%).

Conclusion

In our cohort, Black men with mHSPC presented with a high proportion of de novo metastases and high-volume disease. Treatment outcomes were very favorable with ADT-based regimens. The genomic landscape suggests different molecular profile relative to White patients with potential therapeutic implications.

Abstract PO-190: Health disparities in high-risk lung cancer families and their association with smoking, environmental exposures, and other etiological factors

Lung cancer (LC) is by far the leading cause of cancer-related deaths worldwide. LC survival has only improved marginally over the last decades with the five-year survival rate for LC being lower than most other leading cancer sites. African Americans (AAs) have a higher incidence rate and lower survival rate for LC in comparison to all other racial and ethnic groups in the United States. In addition, incidence rates among AAs and European Americans (EAs) vary with histology of LC. Although tobacco smoking has been identified as the major risk factor for LC, studies have shown there is a genetic component involved in the development of the disease. About 25% of LC cases have at least one first- or second-degree relative, indicating that family history is a relevant risk factor. The goal of this study is to characterize genetic, clinical, and environmental risk factors among individuals of EA and AA ancestry from the high-risk families with LC that could hold important clinical value to address LC disease disparity. Study participants with LC were recruited from a network of 30 hospitals from Louisiana along with multiple states across the country. Study participants with at least two confirmed cases of primary LC within the family were eligible. Participants were divided into two subgroups: Familial (≥2 LC cases/family) and Hereditary LC (HLC families) (≥3 affected LC cases/family). Medical and pathology reports were obtained from hospitals along with demographic and environmental data from the families. A total of 192 study participants (157 EA and 35 AA) from both familial and HLC families from the years 1992 through 2021 were used in this study. Data abstracted from the pathology, clinical reports, and study questionnaire was entered into spreadsheets and analyzed. Histology of LC diagnosis and clinical reports on mutation analysis were documented. The preliminary analyses of results have found that the average age of onset for AAs is significantly lower than in EA (P value &lt; 0.0001). Additionally, while smoking is commonly referred to as a major contributor to LC disparities, AAs were found to have significantly lower pack years of cigarette use than EAs (P value &lt; 0.05). The average age the AA participants ‘begin to smoke' was also found to be significantly lower than EAs (P value &lt; 0.05). The majority of the study participants with LC were diagnosed with adenocarcinoma irrespective of the number of pack-years for cigarette use. Mutation analysis in the clinical report for a small number of study participants in the EA families provided limited information. Additional analysis is ongoing. Clinical and pathological characterization in association with risk factors from high-risk families with EA and AA ancestry will provide us with a better understanding behind the disproportionate distribution of incidence and survival for LC in the AA population.

Citation Format: Grace L. Brandhurst, Angelle Bencaz, Sarah North, Ellen Jaeger, Diptasri Mandal, Joan Bailey-Wilson. Health disparities in high-risk lung cancer families and their association with smoking, environmental exposures, and other etiological factors [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-190.

Immune checkpoint inhibitors (ICI) in advanced sarcomatoid renal cell carcinoma (sRCC): A multicenter study

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Background: Advanced sRCC is an aggressive disease with limited responsiveness to chemotherapy and VEGF-targeted therapies. Subgroup analyses from randomized trials showed improved outcomes with ICI, though sample sizes were relatively small. Methods: We conducted a multi-institutional retrospective analysis of consecutive patients (pts) who had RCC with any sarcomatoid component and received systemic therapy for advanced disease. The pts were classified into ICI+ and ICI- groups (gp) based on whether they had received ICI in any treatment line. Overall survival (OS) was measured from the initiation of first systemic therapy. Time to ICI failure (TIF) was defined as the interval from initiation of ICI to subsequent therapy or death. Survival distributions were estimated using the Kaplan-Meier method. Association between covariates and survival was analyzed using multivariate Cox regression. Two-tailed P < 0.05 was considered statistically significant. Results: 203 pts from 6 US academic cancer centers met the inclusion criteria – 155 in ICI+ gp and 48 in ICI- gp. Overall, 137 (67%) pts were male and 181 (89%) were white; median age at mRCC diagnosis was 59.7 (IQR 52.4-67.7) years; 129 (63%) pts presented de novo with distant metastases, 154 (76%) had clear cell (CC) histology, and 182 (90%) had intermediate/poor risk by IMDC criteria. ICI+ had a higher proportion of purely CC tumors (81% vs 64%, P =.02); other demographic and clinical features were similar between the two gps. After a median follow-up of 48.1 (95% CI 40.7-55.5) months (mos), median OS and response rates were significantly higher in the ICI+ gp (Table). OS benefit, compared to ICI-, was maintained in pts who received ICI in ≥ second line (39.6 vs 7.6 mos, HR 0.33, 95% CI 0.22-0.51, log-rank P <.001). TIF was comparable between pts treated with ICI upfront vs in ≥ second line (6.0 vs 5.3 mos, HR 1.27, 95% CI 0.87-1.85, P =.21). On multivariate analysis, ICI- (HR 2.50, 95% CI 1.61-3.88, P <.001), non-CC histology (HR 3.14, 95% CI 1.98-5.00, P <.001) and sarcomatoid component ≥20% (HR 1.92, 95% CI 1.28-2.90, P =.002) were predictive of all-cause mortality. Among pts with non-CC or mixed histology (n=45), ICI+ had higher OS (18.0 vs 5.5 mos, HR 0.20, 95% CI 0.09-0.44, P <.001) and ORR (44% vs 12%, P =.03), compared to ICI-. Conclusions: Treatment with ICI led to markedly higher survival and response rates in advanced sRCC. OS benefit was maintained with ICI in the second line and beyond. Significant benefit was also noted among pts with non-CC or mixed histology sRCC.[Table: see text]

Differences in the tumor genomic landscape between African Americans (AA) and Caucasians (CA) advanced prostate cancer (aPC) patients (pts) by comprehensive genomic profiling (CGP) of cell-free DNA (cfDNA)

5058

Background: Emerging data suggest differences in the tumor genomic profile of AA compared with CA men with aPC. We hypothesized that there will be significant differences in the tumor genomic landscape between AA and Ca pts as detected by cfDNA CGP. Methods: Pts with aPC and available cfDNA CGP by the Guardant (G360) 73 gene panel were included. In addition, G360 74 gene panel was used to identify CDK12 mutation (not detected in 73 gene panel) in an independent cohort of aPC pts. Barnard’s test was used to evaluate the association between genetic mutation and gene. Genomic landscape was also compared by a Bayesian Network (BN) machine learning approach. Results: A total of 552 pts (125 AA, 427 CA) tested by G360 73 gene panel were included. Multiple genomic aberrations were enriched in AA patients (Table). In the independent cohort of 261 aPC patients (AA=106 pts, CA=155 pts) tested by G360 74 gene panel, CDK12 mutation was significant enriched in AA pts. (9.4% vs. 1.9%, p=0.006). Machine learning analysis supported these results, and will be presented at the meeting. Conclusions: These hypothesis generating data suggest significant differences in the tumor genomic profile between AA and CA pts with aPC. Identification of molecular drivers of tumor progression enriched in AA pts may allow development of tailored systemic therapy for these men, and decrease disparities in disease related outcomes. Data need external validation. PB,RR,MAB contributed equally to this work.[Table: see text]

Family history and pathogenic/likely pathogenic germline variants in prostate cancer patients

BACKGROUND

Recent literature highlights the importance of germline genetic testing in prostate cancer (PCa) patients. Surprisingly, a literature review indicates that family history (FH) records are incomplete in the major published studies from prostate cancer patients.

METHODS

Prospective family history data were gathered from 496 men in a single institution with a personal history of PCa who underwent germline genetic testing using a panel of at least 79 genes. Comprehensive first degree FH were obtained in all PCa of patients and analysis of prevalent FH was assessed at the time of sample collection.

RESULTS

Pathogenic/likely pathogenic variants (PV/LPVs) were not associated with age at diagnosis, race, or presence of metastasis. One or more first degree relatives (FDR) with any cancer was not predictive for germline PV/LPVs for men with PCa (p = .96). Separate analysis of patients with one or more FDR with breast, prostate, ovarian, or pancreatic cancer revealed that only FDR with breast or ovarian cancer was predictive for PV/LPVs (p = .028, p = .015 respectively). Patients with a FDR with breast cancer had 1.8 increased risk of PV/LPVs, and patients with a FDR with ovarian cancer had 2.9 increased risk of PV/LPV.

CONCLUSION

In men with a personal history of PCa, germline PV/LPVs were associated with a FDR with breast or ovarian cancer. Notably having FDRs with PCa does not predict for PV/LPVs. These data emphasize the contribution of FH in a data set with complete ascertainment of FH.

Landscape of circulating tumor DNA (ctDNA) abnormalities in advanced prostate cancer (aPCa): Distinctions in African American (AA) versus Caucasian (Ca) patients

156

Background: AA have substantially higher prostate cancer incidence rates, are diagnosed at a younger age and with a more advanced stage as compared to Ca. However, after adjusting for known prognostic factors, AA have an increased overall survival. We hypothesized that these differences might be due to the underlying changes in the genomic landscape which can be revealed by liquid biopsy. Methods: Real world comprehensive genomic profiling of ctDNA from aPCa patients from two institutions. The first ctDNA results as reported by Guardant 360 panel (Redwood City, CA) were included. Association between genetic mutation and gene were tested using Barnard’s test. To account for multiple testing, we used Benjamini-Hochberg’s False Discovery Rate adjustment across all tests to determine thresholds for false discovery rates. Same analysis was performed using a Bayesian Network Machine learning approach. Results: Overall, 361 patients with aPCa (81 AA and 280 Ca) were included in the analysis. Pathogenic genomic alterations were found in 87.0% of the cases, more frequently TP53 (42.4%), AR (34.1%), PIK3CA (13.9%), BRAF (12.7%), NF1 (10.8%) and MYC (10.0%). Targetable alterations of interest included DNA repair genes [BRCA 2 (7.8%), BRCA 1 (4.4%), ATM (6.4%), CDK12 (2.2%)], PIK3CA/mTOR/AKT (19.1%), PTEN (3.3%) and NTRK (1.9%). MSI-high was found in 4 patients. AA as compared to Ca had a significantly higher prevalence of CDK12 (20.7% vs. 3.8%, p=0.016) and GNA11 mutations (3.7% vs. 0.4%, p=0.0225). BayesNet analysis also supported these results (table). Conclusions: In this dataset, liquid biopsy of ctDNA was useful for genetic characterization of aPCa and reveal differences in the molecular phenotype of AA and Ca in aPCa with potential clinical implications. These findings support ongoing research on the clinical utility of non-invasive genotyping and therapeutic response monitoring with a focus on AA population. [Table: see text]

ctDNA pathogenic variants (PVs) in homologous recombination repair (HRR) genes in patients with metastatic CRPC

138

Background: HRR PVs can serve as predictive biomarkers and two PARP inhibitors are approved for metastasic CRPC (mCRPC) pts. Published data are predominantly focused on tissue-based assays, but obtaining tissue from mCRPC pts is problematic. In a large tissue based series (PROfound), 4047 mCRPC pts had tumor samples submitted for genomic testing but only 69% had interpretable results. No data were published from PROfound enumerating pts without available tissue to submit. Herein we assess frequency of PVs from selected HRR genes using a ctDNA assay. Methods: 292 mCRPC pts at Tulane Cancer Center were assessed for detectable HRR ctDNA changes using the Guardant 360 assay (which assesses the HRR genes BRCA1, BRCA2, and ATM). Results: 20/292 (6.8%) pts had a PV in ATM. However only 4/292 (1.4%) had > 1% mutant allelic fraction. Germline testing occurred in 18/20 of the ctDNA ATM PV pts and 0/18 had a germline PV. The PROfound series had 6.3% somatic PVs in ATM. 18/292 pts (6.2%) had a PV in BRCA2 and 12/292 (4.1%) had a mutant allelic fraction of > 1%. Germline testing was performed in 17/18 with BRCA2 ctDNA PVs and 9/17 had germline PVs. The PROfound series had 9.7% somatic BRCA2 PVs. BRCA1 PVs were detected in 6/292 (2.1%) pts and 3/292 (1%) had a mutant allelic fraction > 1%. 6/6 of the ctDNA PVs has germline testing and 1/6 had a BRCA1 PV. The PROfound series had 1.3% somatic PVs in BRCA1. Conclusions: Using ctDNA essay, it is feasible to measure PVs in only a small subset of HRR genes in mCRPC pts. These assays fail to detect deep deletions, a known and important mechanism of HRR gene loss. The ctDNA mutant allelic fractions are often low. The ability of ctDNA PVs using this assay to predict treatment effects are unknown.

Baseline pathogenic mutations in non-AR/non-TP53 genes and prediction of response to high-dose testosterone

146

Background: The fact that high dose of testosterone (HDT) elicits positive responses in a subset of prostate cancer patients (pts) is surprising and puzzling. Genomics data differentiating responders (Rs) from non-responders (NRs) is sparse. Pts with mutations in DNA repair pathway genes may be particularly sensitive to HDT (see BA Teply et al. Eur Urol 71:499, 2017). Herein we perform exploratory analyses to better understand the role of pathogenic mutations (muts) in ctDNA as a predictive biomarker for patients treated with HDT. Methods: ctDNA essays were performed with the Guardant360 methodology pre-HDT. Point mutations were classified by cancervar (http://cancervar.wglab.org). Truncating mutations (frameshift and nonsense) were manually curated to assess for pathogenicity. All patients had CRPC and were pre-treated with abiraterone and/or enzalutamide. HDT was typically administered as 400 mg testosterone cypionate q 3-4 weeks. Rs were compared to NRs. All Rs had >3 more cycles of HDT and a >50% PSA decline (N = 17). Non-responders had <3 cycles and no PSA decline (N = 23). Only muts with an allelic fraction of >0.5% were analyzed given dubious importance of mutations with lower allelic fractions. Results: AR muts (4/17 vs 6/23 in Rs and NRs) and TP53 muts (10/17 vs 11/23 in Rs and NRs) were similar ( P= 0.85 and 0.49, respectively) but the number of pts with non-AR/non-TP53 muts was distinct (3/17 for Rs, and 12/23 for NRs; P= 0.026). The average number of non-AR/non-TP53 muts (Rs = 0.23 and NRs = 0.83) was higher in the NRs (P = 0.046). When analyzing DNA repair alterations, no differences were noted in those with BRCA1/BRCA2/ATM mutations in the Rs and NRs (1/17 vs 6/23 respectively; P= 0.09). Conclusions: AR and TP53 pathogenic mutations are common in both Rs and NRs but other pathogenic mutations are more common in non-responders. We hypothesize that genetic pathways outside of the AR/TP53 axis drive resistance to HDT. Additional studies are warranted to assess whether or not these pathways drive resistance to HDT. Limitations are acknowledged with regard to the Guardant assay gene selection for CRPC pts.

PD-L1 inhibition with avelumab plus abiraterone acetate or enzalutamide in African Americans with metastatic castrate-resistant prostate cancer (mCRPC)

87

Background: African Americans (AA) are at higher risk for prostate cancer death compared to other ethnic groups in the United States. Early immune-based therapy prolonged overall survival in men with mCRPC and appears to be more pronounced in AA compared to Caucasian men. We sought to explore efficacy of PD-L1 inhibition in AA men with mCRPC. Methods: AA men > 18 years of age and had developed mCRPC on next generation hormonal therapies (NHTs) were eligible for this study. Patients received avelumab 10mg/kg IV every 2 weeks while remaining on NHTs until clinical or radiographic disease progression. This pilot, single-arm phase 2 prospective study was designed to enroll 13 patients with primary endpoint to assess > 50% reduction in PSA (PSA50). Radiographic assessments were planned every 12 weeks until progression or two years, whichever came first. Results: Of the eight patients enrolled, there were three screen-failures: +hepatitis titer (n = 1), rapid clinical deterioration (n = 1) and not confirmed CRPC (n = 1). Median age at time of enrollment was 62 (54-73) with median PSA 7.2 (3.6 – 8.63). Five patients received at least one dose of avelumab and remained on abiraterone acetate with steroid (n = 4) or enzalutamide (n = 1). Median duration on NHTs prior to enrollment was 364 days (95% CI, 260.9-467.1). Median time from screening to cycle 1 was 8 days (3-14). One patient withdrew consent after a single dose of avelumab. Two patients had rapid clinical progression within 8 weeks of starting avelumab. One patient received 9 cycles of avelumab and progressed. One patient experienced a grade 4 adverse event after 2 doses of avelumab with clinical progression during treatment delay. None of the five enrolled patients achieved a PSA50. The median time on study to PSA progression was 35 days (95 CI%, 0-94.8) with median time to radiographic progression of 44 days (95 CI%, 0-118.5). Adverse events occurred in 80% (n = 4/5) of cases. One of the 11 reported grade 3/4 adverse events was related to study drug (G3 hyperglycemia). The study was closed to further accrual prior to the pre-planned completion due to safety concerns related to lack of efficacy of study intervention and rapid clinical progression. Conclusions: The addition of avelumab did not demonstrate clinical activity in AA men with mCRPC who progressed on abiraterone acetate or enzalutamide. The short time interval between PSA progression and radiographic and/or clinical progression is concerning and notable to be much shorter than previously reported pivotal phase III trials. This suggests potential for very significant clinical implications regarding not only future clinical trial designs but also clinical management in this underrepresented ethnicity. We will report updated analysis with longer follow-up (NCT03770455). Clinical trial information: NCT03770455.

18F-fluciclovine positron emission tomography (PET) in metastatic castration-resistant prostate cancer (mCRPC) treated with abiraterone acetate

TPS171

Background: Conventional imaging of prostate cancer has limitations in staging, restaging after biochemical relapse, and response assessment. Functional imaging with positron emission tomography (PET) can target various aspects of tumor biology and has shown to be superior in the detection of prostate cancer compared with conventional computed tomography (CT) and bone scans. 18F-Fluciclovine, a synthetic amino acid transported across mammalian cell membranes by amino acid transporters that is upregulated to a greater extent in prostate cancer cells than in surrounding tissue, is currently approved for PET imaging for patients with biochemical recurrence. The role of 18F-Fluciclovine PET scans in monitoring response to novel hormonal therapies such as abiraterone acetate is unclear. We hypothesize that 1) using 18F-Fluciclovine PET scanning will allow a more sensitive assessment of mCRPC patients at the initiation of systemic therapy with abiraterone acetate and 2) the changes observed in 18F-Fluciclovine PET will correlate better with the serologic changes in PSA, allowing superior disease monitoring, than conventional imaging modalities. Methods: This single-arm, pilot study (NCT04158245) will describe the changes in 18F-Fluciclovine PET scan and compare these results with PSA and conventional computerized tomography (CT) and bone scans, in mCRPC patients treated with abiraterone acetate plus prednisone. Patients must have a detectable baseline PSA of ≥ 2 ng/mL and metastatic disease detected on conventional CT and bone scans. The use of docetaxel in the hormone-sensitive setting is allowed. Twelve patients will be treated with abiraterone 1000 mg daily plus prednisone 5 mg (or dexamethasone 0.5 mg) daily for mCRPC and get 18F-Fluciclovine PET and conventional CT and bone scans at baseline and 12 weeks after starting abiraterone therapy or at disease progression. PSA progression will be defined as a repeated increase in PSA of at least 2 ng/dL and 25% from nadir values, at least 1 week apart, according to PCWG3 criteria and clinical or radiographic progression by RECIST version 1.1. The co-primary objectives of the study include the 18F-Fluciclovine PET changes at baseline and 12 weeks after abiraterone acetate for mCRPC and the comparison between 18F-Fluciclovine PET and conventional scans. Secondary and exploratory endpoints include PSA response, PSA progression and genomic alterations by next-generation sequencing. As of 12 September 2020, this trial is actively enrolling. Clinical trial information: NCT04158245.

Multi-institutional evaluation of the clinical outcomes and genomic correlates of African Americans with metastatic castration-sensitive prostate cancer (mCSPC)

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Background: Prostate cancer incidence and mortality is higher in African American (AA) as compared with non-AA men. The outcomes of mCSPC have significantly improved through treatment intensification yet, AA representation in those studies was suboptimal. We aimed to report the clinical, treatment outcomes and genomic data of AA men with mCSPC. Methods: Retrospective analysis of consecutive AA men with mCSPC at six Academic Institutions. The primary objective was to report the baseline characteristics and treatment patterns of mCSPC AA patients. The secondary objectives included the germline and somatic data and the clinical outcomes including PSA response, progression-free survival and subsequent treatments. Results: A total of 71 patients, median age 63 years (range, 41-84) with 58% Gleason 8-10, initial PSA of 69.8 ng/mL (0.02-7650), 59% with de-novo and 55% with high-volume (CHAARTED criteria; 20% visceral) disease, were included in this analysis. Twenty-two patients (31%) were treated with androgen deprivation therapy (ADT; 67% prior to year 2017), while 24%, 45% and 3% received docetaxel (median 6 cycles), abiraterone acetate and enzalutamide, respectively. Two patients received triplet therapy with ADT/docetaxel plus abiraterone or enzalutamide. Undetectable PSA was achieved in 35% after a median of 8.9 months (1.8-22.3). Among patients with mCSPC who received radiation therapy to prostate (n = 8), 89% had low volume disease. At time of cut off, thirty-two patients developed CRPC and the estimated median time to CRPC was 2.9 years (95% CI, 1.6-4.2). Subsequent therapies (n = 29) included abiraterone acetate (41%), enzalutamide (24%), bicalutamide (10%), radium-223 (7%), chemotherapy (7%), sipuleucel-T (3%) and others (7%). Five patients (8%) had pathogenic germline alterations (n = 2 BRCA1; n = 1 HOXB13, PALB2 and PMS2). Additionally, the most common somatic alterations among tested patients (n = 27) included CDK12, SPOP, TMPRSS2-ERG fusion, and TP53, all in 11% frequency. Of note, n = 2 BRCA1 and n = 1 high MSI/TMB. Conclusions: In one of the largest reported cohorts to our knowledge, mCSPC AA presented with a high number of de-novo and high-volume disease and might harbor a different germline and somatic genomic profile. The outcomes were comparable to contemporary phase III trials with treatment intensification, yet 31% were treated with ADT. Despite the known limitations associated with retrospective analysis, these data support prior observations where AA might have better initial PSA responses to ADT-based strategies compared with Caucasians, requiring further validation.

Family history and pathogenic/likely pathogenic germline variants in prostate cancer patients

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Background: Recent literature highlights the importance of germline genetic testing in prostate cancer (PCa) patients. Surprisingly, a literature review indicates that family history records are incomplete in published studies. Methods: Prospective and complete family history data were gathered from 496 men in a single institution with a personal history of PCa who underwent germline genetic testing using a panel of at least 79 genes (Invitae testing) from 2016-2020. Comprehensive FH were obtained in all PCa patients in this database and analysis of prevalent FH was assessed at the time of sample collection. Age, race, metastastes at any time, and Gleason score were also ascertained. MUTYH heterozygotes were not considered pathogenic. Results: Pathogenic/likely pathogenic variants (PV/LPVs) were not associated with age at diagnosis, race, or presence of metastasis. Men with Gleason scores 8-10 at time of diagnosis were more likely to have PV/LPV ( P= 0.004). One or more first degree relatives (FDR) with any cancer with was not predictive for germline PV/LPVs for men with PCa ( P= 0.96). Analysis of patients with one or more FDR with breast, prostate, ovarian, or pancreatic cancer revealed that only FDR with breast cancer ( P = 0.028) or ovarian cancer ( P = 0.015) was predictive for PV/LPVs. Though one or more FDR with prostate cancer did not predict a PV/LPV in the overall panel, further analysis indicate that a history of a FDR with PCa was predictive for PV/LPV in a DNA damage repair (DDR) gene ( P= 0.044). Conclusions: In men with a personal history of PCa, germline PV/LPVs were associated with a FDR with breast or ovarian cancer. A FDR with PCa was predictive for PV/LPV in DDR genes. These data emphasize the contribution of FH to germline genetic testing results in a cohort with complete ascertainment of cancer in first degree relatives.

Treatment response in the intact primary renal mass (P-Rmass) and its relationship to the overall response to treatment in patients with metastatic renal cell carcinoma (mRCC)

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Background: With the approval of more effective systemic treatments (syst Rx) such as tyrosine kinase inhibitors (TKI) and immune checkpoint inhibitors (ICI), the impact of cytoreductive nephrectomy (CN) on response to Rx and survival remains unknown. The majority of patients (pts) previously enrolled in clinical trials have had radical nephrectomy (RN) or CN prior to syst Rx. Therefore, the response of the P-Rmass to ICIs and the effect of intact P-Rmass on response to syst Rx is not well described. Methods: A retrospective review of 209 pts with mRCC who were treated with ICI in the first or second-line was conducted. Following the appropriate regulatory process, collaborators from 5 US sites collected clinical, pathological, and outcome data via chart review. The response was investigator-assessed for all pts with at least one post-treatment scan or evidence of clinical progression after treatment initiation. Overall radiographic response (ORR) includes complete response (CR) and radiographic response (Rad-resp) to treatment. Disease control rate (DCR) includes CR, Rad-resp, and stable disease. Results: Median age at diagnosis was 63 yrs and 69% were male. 102 pts (49%) had localized disease at diagnosis and underwent radical or partial nephrectomy, 3 (1%) had ablation/radiation of P-Rmass, 26 (12%) had CN, 9 (4%) had CN after an excellent response to syst Rx, 12 (6%) had a previous nephrectomy but developed a new Rmass (measurable target lesion), and 57 (27%) did not have CN and had an intact P-Rmass. 176 (84%) pts had clear cell histology. 27 (14%) and 23 (12%) had known sarcomatoid and rhabdoid features, respectively. Overall, 77 (37%) pts had a measurable Rmass while receiving syst Rx. 84 (40%), 93 (45%), and 10 (5%) pts received ICI (Ipilimumab/Nivolumab or Nivo), TKI, or Pembrolizumab/Axitinib in the first-line. 143 (68%) and 70 (33%) pts received second- and third-line treatment. 103 (72%) and 28 (19%) pts received ICI and TKI in the second-line, respectively. The best ORR and the Rad-resp in the intact P-Rmass in evaluable pts are summarized in the table below. ORR to ICI in the first or second-line were numerically higher in pts with an intact P-Rmass compared to pts who had nephrectomy, but this difference was not statistically significant (p= .38 and .35 respectively). Conclusions: The intact P-Rmass had a good response (62-70%) to the first-line syst Rx. Although the overall Rad-resp rates to ICI are numerically higher in pts with intact P-Rmass, this difference was not statistically significant. [Table: see text]

EPID-03. SINGLE INSTITUTIONAL CLINICAL AND GENETIC ANALYSIS OF METASTATIC PROSTATE CANCER WITH AND WITHOUT BRAIN METASTASES

BACKGROUND

Brain metastases (BMs) from metastatic prostate cancer (mPCa) are rare so little is known about clinical, genetic, and anatomic risk factors (RFs) for developing BMs. This single-center review of mPCa patients evaluates RFs for BM development.

METHODS

We reviewed records of mPCa patients at Tulane from 1991 – 2020 to evaluate disease, treatment, cell free DNA, and germline mutations between men with mPCa without confirmed BMs (smPCa) and men with mPCa and confirmed BMs (mPCaBMs).

RESULTS

We reviewed 580 patients with mPCa, of whom 11 had BMs (1.9%). Median age of stage 4 disease was 60.9 and 67.6 for men with mPCaBMs and smPCa respectively. Most mPCaBMs patients had Gleason 8 disease (81.8%) and higher median initial PSA (32 ng/mL) compared to 52.5% and 22.5 ng/mL for patients with smPCa. The development of castrate resistant disease (p=0.30) and overall survival (p=0.53) did not differ between the two populations. There were no differences in frequency of pathogenic mutations for the 68.9% (mPCaBMs) and 72.7% (smPCa) of patients with available genetic testing. Among the 11 mPCaBMs patients, 81.8% had supratentorial and 45.5% had infratentorial involvement (36.4% both). Forty-five percent had adjacent bony metastasis. Median time from SMs to BMs was 65 months (5.28 – 163.63 months), and median survival after diagnosis of BMs was 6.23 (0.49 – 70.82) months after treatment with WBRT, SRS, or GK.

CONCLUSIONS

The higher incidence of BMs likely reflects Tulane’s aggressive mPCa population. Interestingly 45% of BMs occurred from direct bony extension. Although 45% had infratentorial disease reflecting posterior fossa predilection, 82% of patients with BMs had supratentorial metastases. Our data suggest that men with mPCaBMs have aggressive disease and younger age at diagnosis. Due to sample size, no clinical or genetic statistically significant RFs for BMs were identified.

Outcomes With First-Line PD-1/PD-L1 Inhibitor Monotherapy for Metastatic Renal Cell Carcinoma (mRCC): A Multi-Institutional Cohort

Introduction: The treatment landscape of metastatic renal cell carcinoma has advanced significantly with the approval of combination regimens containing an immune checkpoint inhibitor (ICI) for patients with treatment-naïve disease. Little information is available regarding the activity of single-agent ICIs for patients with previously untreated mRCC not enrolled in clinical trials. Methods: This retrospective, multicenter cohort included consecutive treatment-naïve mRCC patients from six institutions in the United States who received ≥1 dose of an ICI outside a clinical trial, between June 2017 and October 2019. Descriptive statistics were used to analyze outcomes including objective best response rate (ORR), progression-free survival (PFS), and tolerability. Results: The final analysis included 27 patients, 70% men, median age 64 years (range 42-92), 67% Caucasian, and 33% with ECOG 2 or 3 at baseline. Most patients had intermediate risk (85%, IMDC) with clear cell (56%), papillary (26%), unclassified (11%), chromophobe (4%), and translocation (4%) RCC. All patients had evidence of metastatic disease involving the lungs (59%), lymph node (41%), CNS (19%), liver (11%), adrenal gland (11%), and bone (11%). The median time on ICI was 3.1 (0.1-26.8) months, and the median PFS was 6.3 (95% CI, 0-18.6) months. Among the 21 patients with an evaluable response, the best ORR was 33%, including two complete responses and five partial responses. The ORR was 29% (n = 1 complete response, n = 5 partial response) in clear cell and 5% (n = 1 complete response) in non-clear cell RCC. Adverse events (AEs) of any cause were reported in 37% and included fatigue (11%), dermatitis (11%), diarrhea (7%), and shortness of breath (7%). Significant AEs (30%) included shortness of breath (7%), acute kidney injury (4%), dermatitis (4%), Clostridium difficile infection (4%), cerebrovascular accident (4%), and fatigue (7%). Three patients discontinued therapy due to grade 4 AEs. Conclusions: In this multi-institutional case series, single-agent ICI demonstrated objective responses and was well tolerated in a heterogeneous treatment-naïve mRCC cohort. ICI monotherapy is not the standard of care for patients with mRCC, and further investigation is necessary to explore predictive biomarkers for optimal treatment selection in this setting.

Clinical activity of pembrolizumab in metastatic prostate cancer with microsatellite instability high (MSI-H) detected by circulating tumor DNA

To report a multi-institutional case series of patients with advanced microsatellite instability high (MSI-H) prostate adenocarcinoma identified with clinical cell-free DNA (cfDNA) next-generation sequencing (NGS) testing and treated with immune checkpoint inhibitors. Retrospective analysis of patients with metastatic castration-resistant prostate cancer (mCRPC) and MSI-H tumor detected by a commercially available cfDNA NGS assay Guardant360 (G360, Guardant Health) at eight different Academic Institutions in the USA, from September 2018 to April 2020. From a total of 14 MSI-H metastatic prostate cancer patients at participating centers, nine patients with mCRPC with 56% bone, 33% nodal, 11% liver and 11% soft-tissue metastases and a median PSA of 29.3 ng/dL, were treated with pembrolizumab after 2 lines of therapy for CRPC. The estimated median time on pembrolizumab was 9.9 (95% CI 1.0 to 18.8) months. Four patients (44%) achieved PSA50 after a median of 4 (3–12) weeks after treatment initiation including three patients with >99% PSA decline. Among the patients evaluable for radiographic response (n=5), the response rate was 60% with one complete response and two partial responses. Best response was observed after a median of 3.3 (1.4–7.6) months. At time of cut-off, four patients were still on pembrolizumab while four patients discontinued therapy due to progressive disease and one due to COVID-19 infection. Half of the patients with PSA50 had both MSI-H and pathogenic alterations in BRCA1 and BRCA2 in their G360 assays. The use of liquid biopsy to identify metastatic prostate cancer patients with MSI-H is feasible in clinical practice and may overcome some of the obstacles associated with prostate cancer tumor tissue testing. The robust activity of pembrolizumab in selected patients supports the generalized testing for MSI-H.

First-line PD-1/PD-L1 inhibitor monotherapy for advanced renal cell carcinoma (aRCC): A multi-institutional cohort

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Background: Combination regimens containing a programmed cell death protein 1 (PD-1) or a programmed cell death ligand 1 (PD-L1) inhibitor improve the clinical outcomes of previously untreated aRCC. These regimens are clinically active but are associated with adverse events (AEs). One prospective study (KEYNOTE-427) has shown clinical activity of pembrolizumab monotherapy in aRCC. We aimed to describe the utilization and outcomes of single-agent PD-1/PD-L1 in previously untreated aRCC patients (pts). Methods: Consecutive pts treated with front-line PD-1/PD-L1 monotherapy for aRCC were included. Descriptive statistics were used to analyze outcomes including overall response rate (ORR), progression-free survival (PFS) and safety. Results: A total of 28 pts (median age 60; 32% ECOG 2/3; intermediate/poor risk 86%/14%; 35% non-clear cell aRCC) were identified. Common sites of metastases included lung (57%), lymph nodes (39%), bone (21%) and brain (21%). Pts received pembrolizumab (n = 9), avelumab (n = 1) or nivolumab (n = 18) due to pt/physician’s decision (46%), poor performance status (29%) or clinical trial (21%). In evaluable pts (n = 24), the ORR was 33% in ccRCC and 30% in nccRCC. With a median follow up of 13 months (mo), the median PFS was 6.3 mo (CI 95%, 1.5-11.1) and 16 pts progressed on therapy. Frequent AEs (57%) included fatigue (21%), myalgias/arthralgias (11%) and hypothyroidism (7%). No significant grade AEs (G3+) were noted. After progression on PD-1/PD-L1 (n = 16), 39% received a subsequent anti-VEGF (cabozantinib n = 6; sunitinib n = 4; pazopanib n = 1), 42% went to hospice or died and 21% were lost to follow up. Conclusions: First-line single-agent treatment with PD-1/PD-L1 inhibitors showed a favorable safety profile and clinical activity in patients with clear cell and non-clear cell aRCC who were not considered for a combination regimen. [Table: see text]

Comparison of germline mutations in African American and Caucasian men with metastatic prostate cancer

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Background: The relevance of germline mutations in metastatic prostate cancer is well established; however, comparison of germline genetics in African American (AA) versus Caucasian (CA) men with metastatic prostate cancer (PCa) is limited. Methods: Germline data from self-identified AA and CA metastatic PCa patients (pts) were collected from 5 academic cancer centers. Various commercial cancer-specific germline testing panels were used to evaluate 12-86 genes. Pathogenic (P) or likely pathogenic (LP) mutations, and variants of unknown significance (VUS), were reported according to ACMG guidelines. Self-reported family history (FH) was annotated for 99% of pts. Statistical analyses included Chi-squared and Fischer’s exact tests. Results: A total of 821 metastatic PCa pts were assessed: 152 AAs and 669 CAs. For P/LP alterations, AAs had a frequency of 11.2% (17/152) as compared to a frequency of 14.6% (98/669) in CAs (p = 0.302). AA pts were more likely to have a VUS than CA pts, 61% vs 43% respectively (OR = 2.09, 95%CI [1.45, 2.99], p < 0.001). BRCA mutations were similar between races, but AA were more likely to have a BRCA1 P/LP alteration (OR = 6.00, 95% CI [1.33, 27.09], p = 0.025). AA pts were less likely to have a P/LP alteration in a non-BRCA gene (OR = 0.34, 95% CI [0.15, 0.80], p = 0.013). Among DNA repair genes, there were no significant difference between AA and CA pts (p = 0.574); however, there was a trend toward AA pts having fewer P/LP alteration in a non-BRCA DNA repair genes (OR = 0.26, 95% CI [0.06, 1.08], p = 0.071). In pts with >1 first degree relative (FDR) with ovarian cancer, P/LP germline alterations were more likely in CAs (OR = 2.33, 95% CI [1.05, 5.17], p = 0.043); but there were no significant differences in AAs (p = 0.098). Those with >2 FDRs with PCa were more likely to have a P/LP change in CAs (OR = 2.32, 95% CI [1.04, 5.15], p = 0.043), but there were no difference in AAs (p = 0.700). In pts with ≥2 FDRs with breast cancer, P/LP germline alterations were more likely in both AAs (OR = 9.36, 95% CI [1.72, 50.84], p = 0.019) and CAs (OR = 3.92, 95% CI [1.79, 8.59], p = 0.001). Conclusions: We did not observe a difference in the overall frequency of germline P/LP alterations between AA and CA men with metastatic PCa but VUSs were more common in AA men. These AA men have an overall frequency of BRCA mutations similar to CA men; however, BRCA1 mutations were more prevalent in these AAs. Non-BRCA P/LP mutations are significantly less frequent in AA pts. A positive family history of >2 FDRs with breast cancer was associated with P/LP alterations in both AA and CA pts.

Family history and germline alterations in metastatic prostate cancer patients

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Background: Recent literature has highlighted the importance of germline genetic testing in metastatic prostate cancer (PCa)patients (pts). This retrospective study evaluated family history (FH), evaluate treatment outcomes in metastatic patients with pathogenic germline mutations, and compared family history in Caucasian (CA) and Africans Americans (AA). Methods: At Tulane Cancer Center, 428 metastatic PCa pts had germline testing in at least 79 genes. Comprehensive family histories were obtained in all. Analysis of prevalent FH, including breast, ovarian, prostate, and pancreatic cancers was assessed for all metastatic pts. Statistical analyses including chi square were performed. Results: 64 (64/428; 14.9%) pts had at least one or more pathogenic mutations, while 166 (166/428; 38.7%) had were normal. The remaining 199 (199/428; 46.4%) of pts had a variant of uncertain significance (VUS). Pts with a DNA repair pathogenic mutation were more likely to have >2 family members affected by cancer, regardless of cancer type or degree of relationship (p=0.0047); 6 pts without any family history of cancer had a pathogenic mutation. In CA, the presence of either a breast or PCa family history was associated with pathogenic germline findings (p=.022/.0367) However, in AAs neither breast nor prostate cancer predicted pathogenic germline alterations. Conclusions: The correlation between family history of breast and PCa cancer in CA pts with pathogenic mutations is notable as is the finding of >2 family members with cancer predicting germline pathogenic alterations. With AA pathogenic pts, there was no correlation of family history of breast and PCa, which highlights the need to learn more about the genetic factors which influence AA prostate cancer risk.[Table: see text]

Circulating tumor DNA (ctDNA) landscape in metastatic castrate-resistant prostate cancer patients with germline alterations

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Background: Circulating tumor-DNA (ctDNA) in mCRPC patients (pts) provides a viable approach for examining the genetic landscape of prostate cancer. In this follow-up, we report ctDNA variants in germline tested mCRPC pts. Methods: ctDNA alterations in 73 genes were detected using Guardant360 (G360) assays. Alteration types assessed were missense, frameshift, insertions, splice variants, truncations, amplifications (amp), deletions, and other. Pts included in the analysis received germline genetic testing (Invitae Corporation, San Francisco, CA) and ctDNA assays at various treatment timepoints. Statistical analyses were performed using chi-square and fisher exact test with p-value <0.05 for significance. Results: Germline and ctDNA testing was completed in 270 mCRPC pts. 13% (35/270) of pts had pathogenic germline alterations. Germline alterations detected were BRCA2 (43%, n=15), ATM (8.5%, n=3), CHEK2 (8.5%, n=3), and BRCA1 (6%, n=2). Of the 673 alterations detected in G360 assays, TP53 (25%, n=167) and AR (17%, n=117) were most commonly observed. ctDNA alteration breakdown for germline negative/positive pts is summarized in Tables A/B. Germline negative pts had more AR alterations compared to germline positive (p = 0.023). Also, germline negative pts presented with more amps (p < 0.001) and germline positive pts with more frameshift alterations (p = 0.005). The association of ctDNA alteration to clinical outcomes in germline positive/negative pts was also assessed and is ongoing. Conclusions: Pts with germline positive alterations had few somatic AR alterations and higher frequency of deleterious mutation in comparison to their germline negative counterparts.[Table: see text][Table: see text]

Comparison of Caucasian and African-American DNA repair alterations in men with metastatic prostate cancer

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Background: Data on germline DNA repair defects and VUS rates are sparse in African American (AA) men with metastatic prostate cancer (PCa). Methods: Germline testing data from two centers with a significant percentage of metastatic AA PCa patients were combined and compared to Caucasian American (CA) with metastatic PCa. Fourteen canonical DNA repair genes (ATM, BARD1, BRCA1, BRCA2, BRIP1, CHEK2, MLH1, MSH2, MSH6, NBN, PALB2, PMS2, RAD51C, RAD51D) were assessed in all tested patients (pts) using a pathogenic/likely pathogenic (P/LP) classification. Variants of unknown significance (VUS) were assessed in an Invitae-derived dataset with consistent VUS reporting. Results: A total of 105 AA men with metastatic disease were evaluated and 7/105 of these men (6.67%) had P/LP alteration. Among the AA pt alterations, there were 4 pts with BRCA2, 2 pts with BRCA1, and 1 pt with PALB2. A total of 39/417 (9.3%) of CA metastatic patients had P/LP alterations in the canonical 14 genes. No differences were detected in the AA vs CA metastatic comparison (p=0.39). A total of 1/105 (0.95%) AA pts and 23/418 (5.5%) CA had non-BRCA P/LP mutations. The number of non-BRCA P/LP mutations were lower in the AA as compared to the CA men (p=0.045). When evaluating VUS calls in the metastatic AAs using Invitae multi-gene panels, 28/92 (30.43%) pts had a VUS in the canonical 14 genes as compared to 67/366 (18.31%) of the CA men. AAs were more likely than CA to have a VUS (p=0.010). These data indicate that metastatic AA pts and CA are not significantly distinct in the P/LP alterations in 14 canonical DNA repair genes but that there were lower percentages of P/LP in the AA non-BRCA gene subset. Further, when assessing these genes, it is clear that a VUS is more likely to be called in the AA men. Conclusions: Among men with metastatic PCa, AAs have similar rates of inherited P/LP alterations in 14 well accepted DNA repair genes as compared to CA men, however the non-BRCA gene P/LP alterations were less frequent among the AAs. Variants classified as a VUS were clearly higher in these AA pts as compared to the CA pts.

Androgen receptor cfDNA longitudinal mutational analysis in metastatic castrate-resistant prostate cancer

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Background: Androgen receptor (AR) mutations commonly occur in metastatic castrate resistant prostate cancer (mCRPC). Methods: Circulating tumor DNA (ctDNA) data were obtained from Guardant 360 assays throughout the clinical course of mCRPC patients (pts). Retrospective analysis for any pt with ≥ 3 Guardant assays at least 4 weeks apart were reviewed. Patients must have at least 1 AR mutation or amplification to qualify for inclusion. Statistical analyses, including chi-sq and longitudinal analyses, were conducted. Results: Of the 259 patients with Guardant testing, a total of 88 patients had at least 3 Guardant tests; of these, 59 (67%) had at least one AR alteration. Patients had a median of 4 Guardant assays (range 3-10). Patients with AR amplification, AR mutation or both were identified (23, 20, 16 respectively). The most common and clinically relevant AR mutations found alone or in combination with amplification were T878A (22%), L702H(19%), W742C (19%), and H875Y (10%). These particular functional AR mutations occurred alone in 16 patients. Only 3 patients had neither amplification nor common AR mutation. 17/59 patients were found to have at least one common AR mutation and amplification at some point (on same or different Guardant). One patient had seven different AR mutations with no amplification and two other patients had 3 AR mutations. Remainder of patients had either AR amplification or ≤ 2 alternative mutations. Patients with an AR amplification were 0.1138x (95% Cl 0.0289 - 0.4491) significantly less likely of having a common known functional mutation (p <0.002) at any point. Conclusions: Patients with the most frequently identified known functional AR mutations are less likely to have AR amplification in pts with mCRPC; these common AR mutations have been shown to be associated with resistance to 2nd generation androgen deprivation. Further clinical correlation between treatment regimen and %cfDNA of these and other non-AR driver mutations is planned.

Zur Totalsynthese des Human-Big-Gastrins I und seines 32-Leucin-Analogons (Vorläufige Mitteilung) / Total Synthesis of Human Big Gastrin I and the 32-Leucine Analogue (Preliminary Communication)

A new total synthesis of the tetratriacontapeptide amide corresponding to the proposed primary structure of human big gastrin I is described. The synthetic route was based on the preparation of six suitably protected fragments, related to sequence 28 - 34, 23 - 27, 21 - 22, 15-20, 9 - 14, and 1 - 8, to be used as building blocks for the total synthesis. The protecting groups were selected according to the Schwyzer-Wünsch strategy of maximum side chain protection based on tertiary alcohols, also for the imidazol function of histidine. Subsequent assembly of the six fragments by three different pathways using the highly efficient Wünsch-Weygand condensation procedure to ensure minimum racemization, followed by deprotection of the synthetic products via exposure to trifluoroacetic acid and final purification by ion-exchange chromatography on DEAE-Sephadex A-25 and partition chromatography on Sephadex G-25, led to human big gastrin I, homogeneous within the limits of the analytical methods used. The biological activity of the synthetic product proved to be 50 percent higher than that of human little gastrin I. The 32-leucine analogue of human big gastrin I was prepared in the same way.

Genomic copy number alterations in clear cell renal carcinoma: associations with case characteristics and mechanisms of VHL gene inactivation

Array comparative genomic hybridization was used to identify copy number alterations in clear cell renal cell carcinoma (ccRCC) patient tumors to identify associations with patient/clinical characteristics. Of 763 ccRCC patients, 412 (54%) provided frozen biopsies. Clones were analyzed for significant copy number differences, adjusting for multiple comparisons and covariates in multivariate analyses. Frequent alterations included losses on: 3p (92.2%), 14q (46.8%), 8p (38.1%), 4q (35.4%), 9p (32.3%), 9q (31.8%), 6q (30.8%), 3q (29.4%), 10q (25.7%), 13q (24.5%), 1p (23.5%) and gains on 5q (60.2%), 7q (39.6%), 7p (30.6%), 5p (26.5%), 20q (25.5%), 12q (24.8%), 12p (22.8%). Stage and grade were associated with 1p, 9p, 9q, 13q and 14q loss and 12q gain. Males had more alterations compared with females, independent of stage and grade. Significant differences in the number/types of alterations were observed by family cancer history, age at diagnosis and smoking status. Von Hippel–Lindau (VHL) gene inactivation was associated with 3p loss (P<E-05), and these cases had fewer alterations than wild-type cases. The fragile site flanking the FHIT locus (3p14.2) represented a unique breakpoint among VHL hypermethylated cases, compared with wild-type cases and those with sequence changes. This is the first study of its size to investigate copy number alterations among cases with extensive patient, clinical/risk factor information. Patients characterized by VHL wild-type gene status (vs sequence alterations) and male (vs female) cases had more copy number alterations regardless of diagnostic stage and grade, which could relate to poor prognosis.

Cerebellar growth in very low birth weight infants

OBJECTIVE

The aim of this study was to assess cerebellar growth of very low birth weight infants from birth to discharge and compare it with term infants.

STUDY DESIGN

Very low birth weight infants were matched by gender, adequacy of weight to gestational age at birth and postmenstrual ages at hospital discharge to term newborns. Exclusion criteria were central nervous system malformation, peri-intraventricular hemorrhage, cerebellar hemorrhage and meningitis. Transverse cerebellar diameter was measured by cranial ultrasound at birth and at hospital discharge in cases, and at birth in matched controls. Very low birth weight infants had magnetic resonance imaging done in the first year.

RESULT

Cerebellar growth was similar in very low birth weight infants without periventricular leukomalacia and controls, and smaller in cases with periventricular leukomalacia than in controls.

CONCLUSION

We suggest that cerebellar growth is normal in the absence of supratentorial injury.

TP53, EGFR, and KRAS mutations in relation to VHL inactivation and lifestyle risk factors in renal-cell carcinoma from central and eastern Europe

Renal-cell carcinomas (RCC) are frequent in central and eastern Europe and the reasons remain unclear. Molecular mechanisms, except for VHL, have not been much investigated. We analysed 361 RCCs (334 clear-cell carcinomas) from a multi-centre case-control study for mutations in TP53 (exons 5-9 in the whole series and exons 4 and 10 in a pilot subset of 60 tumours) and a pilot 50 tumours for mutations in EGFR (exons 18-21) or KRAS (codon 12) in relation to VHL status. TP53 mutations were detected in 4% of clear-cell cases, independently of VHL mutations. In non-clear-cell carcinomas, they were detected in 11% of VHL-wild-type tumours and in 0% of tumours with VHL functional mutations. No mutations were found in EGFR or KRAS. We conclude that mutations in TP53, KRAS, or EGFR are not major contributors to the RCC development even in the absence of VHL inactivation. The prevalence of TP53 mutations in relation to VHL status may differ between clear-cell and other renal carcinomas.

Cancer testis antigen expression and immune responses by prostate cancer patients: Implications for prognosis and immunotherapy

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Background: Prostate cancer (PC) is the most frequent malignancy in men and it continues to be one of the most common fatal cancers. Treatment options in advanced castration-resistant prostate cancer (CRPC) are limited. Cancer testis (CT) antigens are expressed in a variety of human cancers, but not in normal tissues except for MHC deficient spermatogonia, and represent promising targets for immunotherapy. Little is known about CT antigen expression in relation to disease progression. The aim of this study was to investigate which CT antigens are expressed and immunogenic and hence represent promising targets for patients with prostate cancer and correlate these findings with clinicopathological characteristics. Methods: To determine the expression of 6 CT antigens in prostate cancer immunohistochemistry was performed on tissue micro arrays. We investigated 6 CT antigens (NY-ESO.1, MAGE-C1, MAGE-C2, GAGE, MAGE-A1 and MAGE-A4) in benign hyperplasia (n=45), early (n=388) and late stage (n=71) prostate cancer. To determine the occurrence of spontaneous antibodies against cancer testis antigens, ELISA and Western blot was performed for NY-ESO-1, MAGE-C1 and MAGE-C2 with sera from prostate cancer patients. Results: CT antigens are increasingly expressed in late stage prostate cancers. As an exception we found MAGE-C2 to be expressed early in the course of disease, frequently inducing MAGE-C2 specific antibodies. In later stage metastatic prostate cancer patients NY-ESO-1 is more often expressed, inducing NY-ESO-1 specific antibodies. Conclusions: Cancer testis (CT) antigens are prognostic markers, frequently inducing immune responses and may be suitable for immunotherapeutic intervention in patients with prostate cancer.

No significant financial relationships to disclose.

Pharmacogenetic analyses of hematotoxicity in advanced gastric cancer patients receiving biweekly fluorouracil, leucovorin, oxaliplatin and docetaxel (FLOT): a translational study of the Arbeitsgemeinschaft Internistische Onkologie (AIO)

BACKGROUND

Docetaxel-based chemotherapy regimens have demonstrated activity in advanced gastric cancer (AGC). However, a high rate of grade 3/4 hematotoxicity was reported with these regimens. Our purpose was to identify pharmacogenetic markers with potential to detect patients with increased risk to encounter severe hematotoxicity following treatment with 5-fluorouracil, leucovorin, oxaliplatin and docetaxel (FLOT).

PATIENTS AND METHODS

Polymorphisms of genes involved in DNA repair, drug transport and metabolism were determined in 50 AGC patients receiving FLOT within a phase II trial. DNA was extracted from peripheral blood. Genotyping was carried out using PCR-based techniques.

RESULTS

Patients possessing TS-group A genotypes (2R/2R, 2R/3RC, 3RC/3RC) were at increased risk for grade 3/4 hematotoxicity compared with patients harboring a TS-group B genotype (2R/3RG, 3RC/3RG, 3RG/3RG). In all, 59% (20 of 34) of patients with TS-group A genotypes developed grade 3/4 hematotoxicity compared with 25% (4 of 16) of those having TS-group B genotypes (P=0.035). Grade 3/4 neutropenia occurred in 53% (18 of 34) of TS-group A patients compared with 19% (3 of 16) in TS-group B patients (P=0.032). Multivariate analyses identified TS-group A genotypes as significant predictors of grade 3/4 overall hematotoxicity {odds ratio (OR) 4.62 [95% confidence interval (CI) 1.22; 17.44], P=0.024} and neutropenia [OR 5.74 (95% CI 1.03; 32.08), P=0.047].

CONCLUSION

TS-promoter polymorphisms may be associated with hematotoxicity in AGC patients receiving FLOT.