Spectrum and implications of activating BRAF alterations in advanced prostate cancer (aPC)

220

Background: Activating genomic alterations (GA) in BRAF are rare in aPC and their impact on pathogenesis is poorly understood. However, emerging data suggest that these GA may represent clinically actionable targets (Fenor et al, Clin Transl Oncol, 2022). Using comprehensive genomic profiling (CGP) performed in a single commercial lab, we characterized the GA landscape of BRAF-activated tumors in aPC patients (pts). Methods: Tissue(N=15,864) and liquid (N=7,566) biopsies from aPC pts were profiled using FoundationOne CDx and FoundationOne Liquid CDx CGP assays, respectively. Each assay covers 324 cancer-related genes, including the full coding region of BRAF and introns 7-10, with additional sensitivity in exons 11-18 in the liquid assay. Activating GA were defined as hotspot missense mutations, in-frame indels in the kinase domain, or rearrangements (RE) that preserve the kinase domain. Tissue biopsies from non-aPC cancer types (N= 275,151) were used for comparison. Results: BRAF-activating GA were detected in 520/15,864 (3.3%) tissue biopsies: RE were the most common GA (243 samples, 1.5%), followed by K601E (101, 0.6%), and G469A (58, 0.4%). Median age of pts with BRAF-altered tumors was 69 (interquartile range 63-76), compared to 68 for BRAF wild-type (interquartile range 62-74). Rearrangement breakpoints occurred most frequently in intron 8 (37%), intron 9 (28%), intron 10 (20%), and intron 7 (13%). The most common RE were BRAF N-terminal truncations removing the auto-inhibitory domain (22%), SND1-BRAF fusions (13%), intragenic BRAF deletions of the auto-inhibitory domain (12%), and TMPRS22-BRAF fusions (5%). When studying cases with BRAF-activating GA compared to wild-type, we noted a larger proportion of CDK12 mutations (9.2% vs 5.2%, p=0.018), and a depletion of TMPRSS2-ERG fusions (11% vs 32%, p<0.0001), PTEN GA (17% vs 31%, p<0.0001), and APC GA (4.4% vs 8.9%, p = 0.018); alterations in AR occurred at similar rates (13% vs 13%, p=1.0). In liquid samples, overall BRAF GA were slightly less common (187/7566, 2.5%): 65 (0.9%) RE, 33 (0.4%) K601E, 12 (0.2%) G469A. Examining BRAF-altered samples across all cancer types, aPC had the highest proportions of RE (46%) and one of the lowest frequencies of V600E (0.1%). Conclusions: Activating BRAF alterations are detected in ~3% of aPC, with frequent BRAF-SND1 fusions. BRAF RE represent almost half of aPC BRAF GA, the highest fraction observed across a pan-tumor dataset. In addition, we detected a higher incidence of concurrent CDK12 GA and a lower relative frequency of concurrent PTEN, APC, and TMPRSS2-ERG GA. These findings suggest that genetic activation of BRAF in aPC pts may contribute to tumorigenesis and supports further clinical investigation of therapeutics targeting the MAPK pathway in this molecular subtype.

Prevalence of dietary modification and supplement use in patients with metastatic renal cell carcinoma (mRCC)

662

Background: Mounting data suggests that dietary modification and supplement use, including probiotics, may modulate outcomes with immunotherapy in cancer therapy (Spencer CN et al. Science 2021; Dizman N et al. Nature Medicine 2022). For the first time, we sought to quantify the use of these measures among patients with metastatic renal cell carcinoma (mRCC). Methods: An online survey was administered by Kidney Cancer Research Alliance (KCCure), a non-profit patient advocacy group, between July 22 and Sept 22 to a patient mailing list (N=1,532). Only patients diagnosed with mRCC and under active systemic therapy were included for analysis in the current study. Select questions were directed at dietary modification patterns and supplement usage. Patients were additionally surveyed regarding out-of-pocket spending patterns related to supplement purchases and to what extent they shared information about their supplement intake with their physicians. The student's t-test and Chi-square test were used to compare sociodemographic characteristics between participants who did and did not report supplement intake. Results: Out of 1,062 patients with renal cell carcinoma who participated in this survey, 289 met the inclusion criteria (M:F, 145:143). The median age was 61. The majority of patients identified themselves as white (91%), were from the US (86.8%), and had completed a bachelor's degree (52.9%). 21.1%, 46.1%, and 32.6% lived in urban, suburban, and rural locations, respectively. The most common reported first-line treatments were nivolumab/ipilimumab (32.4%) and axitinib/pembrolizumab (13.1%). 22.4% of respondents reported spending >$100/month on supplements, and 8.3% reported spending >$250/mo. Dietary modifications following a cancer diagnosis were reported by 34.9% of respondents, out of which 19.8% followed the Mediterranean diet and 18.8% adopted a ketogenic diet. 50.8% of respondents reported supplement intake. The most widely utilized supplements were cannabidiol (CBD) oil/marijuana, probiotics, and Vitamin C, reported by 28.0%, 24.2%, and 18.6% of respondents, respectively. 83.4% of respondents noted that they consistently report supplement usage to their physicians. There were no statistically significant associations between supplement use and age, sex, living area, or education. Conclusions: A substantial proportion of patients with mRCC use dietary modification and supplements as an adjunct to their antineoplastic treatment. Interventions such as probiotic use and ketogenic diets, which are the subject of a prospective study in mRCC (NCT05119010; NCT05122546), may already be used by many patients. More careful attention to nutrition and supplement use in clinical trial candidates may minimize the impact of these potential confounders.

A phase I trial to evaluate the biologic effect of CBM588 (Clostridium butyricum) in combination with cabozantinib plus nivolumab for patients with metastatic renal cell carcinoma (mRCC)

TPS4606

Background: Combination therapy with the immune checkpoint inhibitor (ICI) nivolumab (nivo) and the tyrosine kinase inhibitor cabozantinib (cabo) is a new standard of care for first line treatment of patients with clear cell mRCC. However, despite the improved clinical benefit obtained with this regimen, a subgroup of patients still presents with progressive disease as best response (Choueiri et al NEJM 2021). There is now evidence supporting the role of the gut microbiome in mediating ICI activity (Routy et al Science 2018) and certain bacterial species, such as Bifidobacterium spp. in predisposing clinical response in patients with mRCC receiving ICIs (Salgia et al Eur Urol 2020). Moreover, recent evidence from a phase I clinical trial suggests that the addition of CBM588, a live probiotic comprised primarily of Clostridium butyricum, can enhance clinical response in patients with mRCC receiving nivolumab plus ipilimumab without incurring added toxicity (Meza et al ASCO, 2021). Herein we present the study design of an ongoing phase I study evaluating the biological effect of CBM588 in combination with cabozantinib plus nivolumab in patients with mRCC. Methods: This is an open label, randomized, single institution phase 1 trial for patients with confirmed mRCC with clear cell, papillary, or sarcomatoid components, who have not received prior systemic therapy for metastatic disease. A total of 30 eligible patient will be randomized 1:2 to receive either cabo/nivo at the standard dose/schedule (40mg PO QD and 480mg IV /4wks, respectively) alone or with CBM588 dosed at 80mg PO bid. The primary objective of the study is to determine the biologic effect of CBM588 with cabo/nivo in the modulation of the gut microbiome. This will be done by assessing the changes in Bifidobacterium spp. abundance and Shannon index (a measure of microbiome diversity) in stool specimens. Stool will be collected for bacteriomic profiling at baseline and after 12 weeks of treatment. Metagenomic sequencing will be performed using previously published methods (Dizman et al Cancer Med 2020). Secondary objectives include determining the effect of CBM588 on (1) clinical efficacy, through overall survival, response rate, and progression-free survival; (2) systemic immunomodulation, through assessment of changes in circulating Tregs, circulating cytokines/chemokines, etc; and (3) toxicities. A two-group t-test with a one-sided type I error of 0.05 will be used to assess the study primary endpoint. Clinical trial information: NCT05122546 .

Transcriptomic profiling identifies genomic markers associated with benefit from stereotactic body radiation therapy (SBRT) in oligoprogressive metastatic renal cell carcinoma (mRCC)

4555

Background: Addition of SBRT to systemic therapy in oligoprogressive mRCC has been shown to prolong the duration of systemic treatment (Cheung et al Eur Urol 2021; De et al BJUI 2021). To date, the genomic predictors of benefit are unknown. We hypothesized that hypoxia-related genes would be associated with lesser benefit from SBRT. Methods: We retrospectively identified patients (pts) with mRCC who had oligoprogressive disease (progression of < 5 sites) while on systemic treatment and received SBRT without any systemic treatment change or interruption. Clinicopathologic characteristics, whole exome and transcriptome sequencing (Ashion Analytics) data were collected. Duration of systemic therapy (DOT) was quantified as systemic treatment duration prior to oligoprogression (DOT[P]) and after completion of SBRT (DOT[S]). The ratio of DOT[S]/DOT[P] was calculated and patients with a ratio ≥ 1.0 were considered to derive greater benefit from SBRT. The frequency of specific DNA alterations and RNA expression of pts above and below a DOT[S]/DOT[P] threshold of 1.0 was compared using a two-tailed Fischer’s exact and student’s t-test, respectively. Results: In this study, 23 mRCC pts who had oligoprogression during systemic treatment and received SBRT were identified. Within this cohort 16 pts (69.6%; M:F, 12:4) had available genomic data. Median age was 70 years and the most common histology was clear cell (87.5%). At the time of oligoprogression 11 pts (68.8%) were on immunotherapy, 4 pts (25.0%) were on targeted therapy. Median DOT[S] and DOT[P] were 12.6 months (range,0.7-46.3) and 13.4 months (range, 0.5-26.9), respectively, with a median DOT[S]/DOT[P] ratio of 1.4 (range,0.01-3.8). The most commonly mutated genes were VHL (56.3%), PBRM1 (37.5%), and SETD2 (37.5%). Alterations in VHL, PBRM1 and SETD2 were seen in 66.7% vs 42.9%, 33.3% vs 43.9%, and 44.4% vs 28.6% in patients with greater vs lesser benefit from SBRT, respectively (p≥0.05for each). Transcriptomic analysis was available in 9 pts and 1580 genes were noted to be differentially expressed between the groups (p < 0.05). Limiting scope to cancer genes in the COSMIC database, pts with lesser benefit from SBRT had higher expression of CDKN1B, CNBP, and FOXO3 whereas pts with greater benefit had higher expression of RNF43, POLD1 and PBRM1 (p < 0.05 for each). Gene set enrichment analysis showed a trend towards increased expression of hypoxia related genes in pts with lesser benefit. Conclusions: Our data align with existing studies supporting the role of SBRT in oligoprogressive mRCC. In addition, while clinical benefit from SBRT appears to be independent of DNA-level alterations, transcriptomic analysis revealed significant differences in gene expression. Hypoxia-associated signatures may be associated with lesser benefit from radiotherapy.

Prospective assessment of a smartphone-app based mindfulness program for patients with metastatic renal cell carcinoma (mRCC)

324

Background: mRCC is associated with high rates of distress, high levels of symptom burden, and broad impairments in quality of life. In the setting of localized breast cancer, a smartphone application directed at enhancing mindfulness has been developed from a Mindfulness-Based Cancer Recovery program demonstrated to mitigate these factors (Utkarsh et al. Digital Health 2021); we sought to determine if the benefit of a similar application could be translated to patients with mRCC. Methods: Patients were recruited across two sites in the US and Brazil, and were eligible for the study if they had been diagnosed with mRCC, were receiving immunotherapy, reported clinically-relevant anxiety, had a smart phone with internet access, were currently not engaging in meditation, and had not participated in a mindfulness program in the past 5 years. Patients were asked to participate in mindfulness app-based activities for 20-30 minutes each day guided by the Mindfulness-Based Cancer Survivorship Journey program within AM Mindfulness smartphone app (AmDTx™), for a minimum of 4 days per week, over a period of 4 weeks. The application leads the patient through exercises in guided meditation and suggestions for cancer/cancer symptom coping. Patients were assessed at baseline and 2-weeks after using the 4-week smartphone-app based intervention using the Fear of Cancer Recurrence-7 and Functional Assessment of Chronic Illness Therapy-General scales. Reported data is evaluated using paired t-tests with a p-value of < 0.05 considered significant. Results: A total of 23 patients have been recruited to date. Median age was 59 years old; most were male (52%), white/Caucasian (52%), married (69%) and college educated (82%), and primarily receiving treatment with nivolumab (34%) or nivolumab/ipilimumab (30%). The majority of patients (78%) expressed satisfaction and engaged with the intervention; however, a minority (13%) noted that the intervention reminded them of their cancer diagnosis, which was seen as a negative aspect. Preliminary analyses of data after two weeks of the intervention have demonstrated a statistically significant decreases in fear of cancer progression (mean differences: baseline = 22; week 2 = 18, p = 0.012) and increases in quality of life (mean differences: baseline = 77; week 2 = 85, p = 0.001) over time. Physical and emotional well-being also showed significant improvement over time. Complete data with 12 weeks of follow-up will be presented at the meeting. Conclusions: This is the first study to implement an evidence-based, smartphone-accessible psychosocial support tool among mRCC patients. After only two weeks, we noted significant improvements in the fear of cancer progression and quality of life. This preliminary data suggests that this type of low-cost, mobile-app based intervention was acceptable to patients and may be effective at addressing psychosocial distress

Characterization of aberrant alternative splicing landscape in patients with renal cell carcinoma (RCC)

386

Background: Aberrant alternative splicing (AS) events have been implicated in the initiation and progression of various cancers; however, the detailed nature of their role in RCC is yet to be fully elucidated. Our study aims to characterize AS events in RCC tumors using a novel AS pipeline (Bisbee). Methods: We retrospectively identified patients (pts) with RCC who had tumor-normal whole exome sequencing and tumor whole transcriptome sequencing (GEMExtra, Ashion Analytics) performed as part of their routine clinical care. AS events from RNA sequencing data were identified and further characterized as (1) alternative splice 3’ site (A3), (2) alternative splice 5’ site (A5), (3) exon skipping (ES), (4) intron retention (IR), and (5) mutually exclusive exons splice events (MUT). The Bisbee outlier analysis was performed against normal kidney tissues from the GTEx tissue library to further identify tumor-associated splice events. Outlier splice events were categorized as either non-coding/protein loss/silent, isoform switch, novel, or unknown. Results: Overall, 147 RCC pts (77% male) with RNA sequencing data were included in this analysis. Median age at diagnosis was 60 (range 31-94) and 97% of pts had metastatic RCC. The distribution of histology was 85% clear cell RCC followed by 11% papillary RCC. The AS analysis identified 25,928 outlier splice events. Approximately 60% of these were predicted to be protein-coding events, with the majority arising from IR and ES. These were followed by A3, A5, and MUT, in descending order of frequency. We also examined tumor-associated novel outlier events where 70% of analyzed RCC tumor samples noted 34 tumor-associated novel events were present, shared in most of the cohort and found an enrichment for IR events leading to frame disruptions. Data of splice variants will be presented at the meeting. Conclusions: In depth examination of this large cohort suggests that IR resulting from AS events occur frequently within RCC. Further efforts to investigate the association of AS events and clinical outcomes are underway.

Association of intra-tumoral microbiome and response to immune checkpoint inhibitors (ICIs) in patients with metastatic renal cell carcinoma (mRCC)

372

Background: Multiple studies have suggested that the gut microbiome plays a modulatory role in ICI activity and that specific bacteria and/or cumulative microbial diversity may drive response in patients (pts) with mRCC (Routy et al Science 2018; Salgia et al Eur Urol 2020). Even though the tumor microenvironment has substantial bacterial proliferation (Heymann et al Cancer L. 2021), there is a paucity of data assessing the impact of intra-tumoral microbiota in response to ICI therapy. In this study, we sought to explore this association in pts with mRCC. Methods: Pts diagnosed with mRCC who had available RNA sequencing (RNA-seq) data collected in the course of routine clinical care and who were treated with ICIs were retrospectively identified.Intra-tumoral microbiome analysis was performed on formalin-fixed paraffin-embedded samples. Following quality and adapter trimming, RNA-seq reads were mapped to a human genome to filter host reads using the Burrows-Wheeler alignment (BWA) tool. Taxonomic classification was performed using Kraken2 and the absolute abundances of species were estimated using Bracken. The relative abundances among all non-human species were calculated. Statistical testing with Student’s t-test was performed to compare the relative abundance for all species seen within pts who responded to ICIs and those who did not. Results: Among the 28 pts (22:6, M:F) included in this analysis, 24 (86%) had clear cell histology and 20 (71%) were IMDC intermediate/poor risk. All of the samples were collected prior to starting treatment with ICIs and the majority of these (57%) were collected from the primary site. 11 pts (39%) received ICIs as first line treatment and 17 (61%) as second line. Clinical response was seen in 50% of pts included in the study and the most common rendered treatment was nivolumab (17 pts). In the overall cohort, Cutibacterium acne, Moraxella osloensis, and Pasteurella multocida had the highest relative abundances. Additionally, significant differences in relative abundances of specific bacteria were found between ICI responders and non-responders. Among these, Stenotrophomonas maltophilia (p = 0.037) and Corynebacterium sp. zg-917 (p = 0.035) had significantly higher relative abundances in pts who responded to ICIs. Conclusions: This is the first study evaluating the association between intra-tumoral microbiome and response to ICIs in pts with mRCC. Among bacteria associated with response, several have particular relevance – for instance, Corynebacterium spp. have been studied for decades as a possible adjunct to immunotherapeutic agents such as BCG. Efforts are ongoing to validate these findings in a larger cohort.

Prolonging utilization of systemic therapy in oligoprogressive metastatic renal cell carcinoma using stereotactic body radiation therapy

336

Background: SBRT in indicated for the management of locally recurrent and oligometastatic mRCC as per National Comprehensive Cancer Network guidelines. Our study evaluates both the efficacy of radiotherapy (RT) in prolonging systemic treatment along with RT toxicity in the oligoprogressive RCC setting. Methods: A single institution retrospective data collection was performed in which we identified mRCC patients who experienced oligoprogression (defined as <1 sites of progressive disease) while on an FDA approved systemic therapy and were concurrently treated with SBRT, while remaining on the same therapy. Clinicopathologic characteristics and SBRT-related data along with duration of systemic therapy (DOT) were collected. DOT was then quantified into two categories which included the duration of systemic therapy prior to oligoprogression (DOT[P]) and duration of systemic therapy after completion of SBRT (DOT[S]). The ratio of DOT[S]/DOT[P] was calculated to determine the impact of SBRT on systemic treatment prolongation. Results: 23 patients diagnosed with mRCC meeting criteria were identified, 91% (n = 21) with clear cell histology and 9% (n = 2) with papillary histology. At the time of oligoprogression, 15 patients (65%) were on immunotherapy, 7 patients (30%) were on targeted therapy, and 1 patient (5%) was on combination therapy. We noted the preponderance of patients were on a first-line therapy at the time of oligoprogression (n = 10, 43%). A median of 2 (range, 1-3) lesions were treated per patient, with lung being the most frequent site (n = 14, 40%). The median total dose of SBRT was 30 Gy (range, 27-50 Gy) with a median dose per fraction of 6 Gy (range, 3-12 Gy). SBRT related toxicities, all of which were grade <2, were noted in 5 patients (22%), of which fatigue was the most frequent side effect (n = 3, 13%). Median DOT[S] was 13.4 months (range, 0.5-37.7 months) and the median DOT[P] was 12.8 months (range, 0.4-46.3 months). Results demonstrated a median DOT[S]/DOT[P] ratio to be 1.3 (range, 0.01-25.8). Conclusions: Based on our data, we discovered the addition of SBRT to systemic therapy during oligoprogression is not only well-tolerated, but that this treatment had clinical benefit in prolonging time on systemic therapy for patients with mRCC. The utilization of SBRT may prolong lines of therapy, thereby decreasing additional toxicities associated with exposure to new regimens.

Waning efficacy of COVID-19 vaccination at six months in patients (pts) with genitourinary malignancies

185

Background: Short-term effectiveness of COVID-19 vaccination is widely demonstrated, but the emerging real-world data suggest that immunity may wane over-time (Levin et al. NEJM 2021). Herein we aimed to explore the long-term efficacy of the COVID-19 vaccination among pts with genitourinary cancer. Methods: In this study, pts with genitourinary malignancies (prostate, kidney, and bladder cancers) who had not received COVID-19 vaccination were included. Blood samples were collected prior to and after one dose of either an adenovirus- or mRNA-based COVID-19 vaccine at the 2- and 6-month timepoints. Additional blood samples from pts receiving systemic treatment were collected at 3 consecutive therapy cycles following vaccination. Antibody titers were assessed using the SCoV-2 Detect IgG ELISA assay and results were reported as immune status ratios (ISR). T-cell receptor (TCR) repertoire sequencing was performed using the MiXCR software (MiLabs) and custom strips were used to assess TCR abundance and homology clustering. Results: A total of 183 pts were enrolled, and 136 pts provided baseline blood samples. Among these, 59 (8:51 F:M) provided samples for both the 2- and 6-month timepoints by the 10/6/2021 data cut-off. In this subset of pts, median age was 66 (range 48-85) and 33 (55.9%), 25 (42.4%), and 1 (1.7%) pts had prostate, kidney, and bladder cancer, respectively. A majority of the pts (93.2%) were on systemic treatment with 23.7% on immune checkpoint inhibitors, 18.6% on targeted agents, and 1.7% on chemotherapy. The most commonly administered vaccines were BNT162b2 (61.0%) followed by mRNA-1273 (37.3%) and Ad26.COV2.S (1.7%). The mean (±standard deviation) ISR values at baseline and 2 months were 0.68±1.59 and 6.62±1.75, respectively. At the 6-month timepoint, mean ISR was 5.46±1.61; this was significantly lower than the 2-month antibody titers (p < 0.0001), and reflects a reduction of 17.6%. Further data on TCR sequencing will be presented at the meeting. Conclusions: To our knowledge, this is the first data assessing the long-term serologic outcomes of COVID-19 vaccination in pts with cancer. Our data suggest waning immunity over time in cancer pts. Strategies to prolong host immunity against SARS COV-2 (e.g., booster vaccination) are likely warranted.

Characteristics associated with common reasons to pursue genomic profiling among patients with metastatic genitourinary cancers

327

Background: Patients with cancer may possess limited knowledge of emerging modalities in oncology, including genomic profiling (GP) tests, which can create barriers to shared decision making. Effective provider communication can address such barriers but little is understood regarding patients’ perceptions of GP. Methods: In this cross-sectional study, patients who were diagnosed with advanced genitourinary cancers (bladder, renal, and prostate cancers), and were referred for GP responded to a survey to assess reasons to pursue such testing. Clinicopathologic characteristics were collected via chart review. Kolmogorov-Smirnov tests were used to assess associations between reasons to pursue GP and patient characteristics. Results: Data was obtained from a sample of 126 patients (gender: 75% M, 25% F; average age: 67; marital status: 78% married; education: 76% some college; histology: 67% renal cell carcinoma, 19% urothelial, and 14% prostate). The most common reasons to pursue GP by patient response were: to guide treatment (73%), to improve treatment response (32%), to follow physician’s indication (27%), to predict treatment response (23%), to learn about their disease (19%), and to contribute to the science (12%). Notably, older age was significantly associated with three reasons (guide treatment, P = 0.001; physician’s indication, P = 0.03; contribute to the science, P = 0.001). No association was found among younger patients. A higher level of education was associated with the desire to guide treatment (P = 0.001). In contrast, a lower level of education was associated with physician’s indication (P = 0.002). Conclusions: This study highlights important associations between reasons to pursue GP and age and level of education. Differing strategies for information delivery could be considered when communicating GP benefits to older patients and to patients with lower levels of education.

Intestinal microbiome associated with development of grade 3/4 adverse in patients with metastatic renal cell carcinoma (mRCC) treated with nivolumab plus ipilimumab (N/I) and probiotic support: Results from a phase Ib study

374

Background: Treatment with N/I with the addition of CBM588, a live bacterial product comprised primarily of Clostridium butyricum, improved PFS and RR versus N/I alone when used as first line treatment for patients with mRCC (Meza et al ASCO 2021). Increased abundance of certain bacterial species in the gut microbiome have been associated with the development of treatment related adverse events (TREAs) in lung cancer patients receiving immunotherapy (Chau et al BMC Cancer 2021). However, this association has not yet been delineated in the setting of mRCC. Here, we present results of an exploratory analysis assessing the differences in stool microbiome composition between patients who experienced grade (G) 3/4 TREAs and those who did not. Methods: Patients were randomized 2:1 to receive N/I with or without CBM588. Stool collection for bacteriomic profiling was planned at baseline and after 12 weeks of therapy for all randomized patients. Whole metagenome sequencing was performed using previously published methods (Dizman et al Cancer Med 2021) and differences in microbiome composition were measured based on the occurrence of G 3/4 TREAs. Results: 30 patients were enrolled and 29 included in the study. At the time of data cutoff (April 15, 2021) the median follow up was 12.2 months (95% confidence intervals [CI], 10.6-13.8). Grade 3/4 TRAEs were experienced in 52, 50, and 53% of patients in the overall cohort, control, and intervention arms, respectively (p = NS). Among the most common G 3/4 TRAEs, subjects experienced fatigue, diarrhea, and hyperglycemia. Patients with a complete set of stool samples were included for the microbiome analysis (n = 26). In patients who experienced G 3/4 TRAEs, a significantly greater baseline abundance of Escherichia coli, Klebsiella spp. and Blautia spp. (p = 0.02, 0.03, 0.05) were seen when compared to those not experiencing G 3/4 TRAEs. In contrast, Bacteroides intestinalis and B. thetaiotamicron, were observed in significantly higher abundances in baseline stool specimens of patients who did not experience G 3/4 TREAs (p = 0.03 for both). No significant differences were seen for any of these species at the 12-week timepoint. Conclusions: We are among the first to investigate the differences in baseline stool microbiome in mRCC patients experiencing G 3/4 TRAEs while receiving immunotherapy. Our results suggest that certain taxa of bacteria are predictors of the development of serious TRAEs. Larger cohorts are needed to corroborate these findings. Clinical trial information: NCT03829111.

Changes in perception of immunotherapy over time among patients with advanced genitourinary cancers

328

Background: Previous studies have shown that a significant proportion of patients with metastatic genitourinary cancers harbor inaccurate expectations of cure prior to starting treatment with immunotherapy. This study sought to compare changes in perceptions of immunotherapy reported before, and three months after, the start of therapy, as well as treatment side-effects and quality of life. Methods: This longitudinal study enrolled patients diagnosed with advanced genitourinary cancers (bladder, renal, and prostate cancers) prior to commencing immunotherapy. Patients’ perceptions were assessed prior to starting treatment (T0) and three months later (T1). Patients responded to the same survey at both time points assessing expectations of side effects, clinical outcomes (expectation of cure) and quality of life (Functional Assessment of Chronic Illness Therapy-General). Results: Among the 30 patients enrolled, the median age was 67 years old (range, 44-91); most were male (70%), married (80%), and well-educated (70%). Renal cell carcinoma (70%) was the most common form of cancer. Before starting immunotherapy (T0), patients expected (1) fewer side effects (83%) compared with other types of cancer treatment, (2) great efficacy in preventing tumor progression (90%). and (3) increased survival (90%). Notably, the expectation of cure with immunotherapy treatment had changed over time (T0 = 24% vs T1 = 7%; P = 0.001) and overall quality of life had increased (median at T0 = 90 vs T1 = 98; P = 0.01). Three months into treatment (T1), patients perceived themselves as less active (T0 = 70% vs T1 = 63%; P = 0.02), however just 16% reported severe side effects, including fatigue (10%) and diarrhea (10%). In general, patients were satisfied with the management of these side effects (60%). The majority of patients perceived improvement in their condition (50%) and were satisfied with their treatment (60%). Conclusions: This longitudinal study suggests that inaccurate perceptions of cure with immunotherapy may recede over time, with an increased proportion of patients estimating a more accurate (and lower) chance of cure after 3 months of treatment. Patients also reported improved quality of life despite these adjusted expectations of cure.

Association between TERT promoter mutations and clinical outcome with immune checkpoint inhibitor therapy for advanced urothelial cancer

561

Background: Recently published data suggests that the presence of a TERT promoter mutation is predictive of superior overall survival (OS) in patients (pts) with advanced/metastatic bladder cancer (mUC) treated with an immune checkpoint inhibitor (ICI) (Kouchkovsky et al, JITC 2021). We aim to validate the results of this study in a large independent cohort. Methods: Pts with mUC treated at two tertiary cancer centers with available genomic data collected in the course of routine clinical care were identified retrospectively. Pts that had received at least one line of ICI therapy in the metastatic setting were selected. Demographic and treatment data were collected, with pts divided into two groups based on the presence or absence of TERT mutation status ( TERTm or TERTwt, respectively). We evaluated OS from diagnosis of at least muscle invasive disease, progression free survival (PFS), and objective response rate (ORR) with ICI therapy across the two groups. OS in our cohort was compared with findings from pts with bladder cancer in The Cancer Genome Atlas (TCGA) database. Results: From our combined data sets, a total of 166 pts had available genomic data, with 64 TERTm pts (52:12 M:F) and 58 TERTwt pts (32:26 M:F) meeting criteria for inclusion. Median age at diagnosis was 67 in both groups. The site of primary disease was bladder in 54 (84%) TERTm vs. 41 (71%) in TERTwt; 10 (16%) and 17 (29%) had upper tract disease, respectively. 47 (73%) TERTm pts and 40 (69%) TERTwt pts had pure urothelial disease; 17 (27%) and 18 (31%) pts had mixed/pure variant histology, respectively. 37 (58%) and 42 (72%) pts received first-line ICI therapy whereas 27 (42%) and 16 (28%) received subsequent-line therapy in TERTm and TERTwt, respectively. At the time of analysis, there were 24 (38%) patients alive in TERTm, and 23 (40%) patients alive in TERTwt. OS was 35 vs. 36 mos (95% CI 0.62-1.51, P=0.66) in TERTm and TERTwt, respectively. PFS on ICI therapy was 4.6 vs. 5.3 mos (95% CI 0.58-1.34, P≥0.99) in TERTm and TERTwt, respectively. ORR was 75% in TERTm and 50% in TERTwt (P=.004). OS in the TCGA database was 35 mos in TERTm and 47 in TERTwt (P=0.19) from a total of 311 and 127 pts, respectively. Conclusions: In contrast to previously published data, our data show no difference in OS and PFS on the basis of TERT mutational status in pts with mUC treated with ICI therapy. Further analysis from larger datasets is needed to reconcile the role of TERT mutations within this patient population.

Abstract LB196: Comparison of whole exome sequencing and targeted sequencing in patients with advanced bladder cancer

Background: Next generation sequencing (NGS) to identify genomic alterations (GAs) in tumor samples are increasingly used in clinical practice. Targeted sequencing (TS) or whole exome sequencing (WES) are used by various commercially available platforms. Differing methods often result in poor inter-reproducibility, even when testing the same tissue. Bladder cancer has substantial genetic heterogeneity as compared to many other malignancies. The purpose of this study is to compare WES and TS in bladder cancer. Methods: Patients with advanced bladder cancer who had undergone tissue WES (GEM ExTra®) or TS (FoundationOne CDx® [FMI]) in the course of routine clinical care were assessed. Genes with at least one detected GA were selected, with others excluded. All detected GAs were classified as being detected on TS only, WES only, concordant (detected on both platforms), or partially concordant (different GAs detected within the same gene). Variants of uncertain significance were excluded for this study. Results: In our series, 25 patients had WES and 42 patients had TS - 14 patients (21%) had both tests performed. A total of 88 genes were detected to have at least one GA across all samples. Of all detected GAs, 66/162 (41%) were concordant, with 45/162 (28%) and 51/162 (31%) of GAs detected exclusively by WES and TS, respectively. The genes with the highest proportion of concordance when detected, were TERT (70%), TP53 (85%) and ARIDA1A (50%). SOX4 and E2F3 were detected on WES only, while RBM and CHEK2 were detected on TS only. Notably, six TP53 GAs were detected exclusively on TS. TP53, TERT, MLL2/KMT2D, ERBB2 were each partially concordant on one occasion. The difference in the rate of concordant GAs in samples from the same collection site and date (41%), as compared to those in which both differed (35%) were not statistically significant (p=0.54). Conclusions: Although the majority of GAs identified were concordant, each platform exclusively identified GAs with varying clinical significance. SOX4 and E2F3 mutation, shown to correlate with invasive potential in bladder cancer, were detected exclusively on WES. In contrast, RBM and CHEK2 (of known significance in melanoma and breast cancer) were found exclusively on TS. Larger series are needed to further establish the concordance of these approaches.

Citation Format: Neal Shiv Chawla, Zeynep Zengin, Ameish Govindarajan, Sumanta K. Pal. Comparison of whole exome sequencing and targeted sequencing in patients with advanced bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB196.

Efficacy of anti-PD(L)1 therapy for patients (Pts) with advanced urothelial carcinoma (aUC) with primary resistance to platinum-based chemotherapy (PC)

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Background: PC remains standard first-line (1L) therapy for aUC. Approximately 15% of pts exhibit primary resistance (P-R) to PC and ∼25% progress by 4 months. PD(L)1 inhibitors yield objective response rates (ORR) of ∼20% in pts with progression after PC; however, it is unclear if this benefit extends to pts with P-R to PC. We examined the efficacy of anti-PD(L)1 in pts with aUC who experienced P-R to 1L PC. Methods: We conducted a multi-institutional retrospective study of pts with aUC who experienced P-R to PC and were subsequently treated with single-agent anti-PD(L)1 therapy. Eligibility included pts with unresectable or metastatic disease diagnosed after January 1, 2017. P-R to PC was defined as radiographic progression by RECISTv1.1 within 12 weeks from initiation of PC. Pts who developed metastatic disease while receiving (neo)adjuvant PC were eligible. Clinicopathologic variables were collected. ORR to anti-PD(L)1 was the primary endpoint. Secondary endpoints included time to treatment failure (TTF, defined as time from start of anti-PD(L)1 therapy to next line of therapy, hospice or death) and overall survival (OS) were estimated using Kaplan-Meier method. Multivariate (MV) analysis using Cox regression evaluating factors associated with OS was performed. Results: Overall, 42 pts were included: 74% male, median age 65 (28-90); 79% ever smokers; 21% mixed histology; 31% received definitive locoregional therapy. Metastatic sites at diagnosis of aUC included: lymph node only (19%), liver (29%), bone (38%) and lung (33%). At diagnosis of aUC, ECOG PS was 0 in 26%, 1 in 52% and unknown in 21%. 1L PC included cisplatin (76%) and carboplatin (24%) based regimens. Anti-PD(L)1 was received either 2L (98%) or 3L (2%). Overall, ORR to anti-PD(L)1 was 17%: CR (2%), PR (14%), SD (14%), PD (57%) and unknown (12%). Of the 24 pts with PD as best response to anti-PD(L)1, only 9 (38%) received subsequent therapy. Overall, median TTF was 4.2 mo (95% CI 2.8-6.7 mo) and median OS was 7.4 mo (95% CI 4.2-11.1 mo). ORR in patients with a PDL1 combined positive score ≥ 10% (n=6) was 0%: 1 SD and 5 PD. MV analysis for OS from start of anti-PD(L)1 is shown (Table). Conclusions: P-R to PC portends a poor prognosis in pts with aUC. While a subset of patients may respond to anti-PD(L)1 therapy, the majority of pts do not derive benefit. Alternative agents, e.g. antibody drug conjugates and FGFR inhibitors, and combination-therapy should be investigated for this high risk population.[Table: see text]

A phase 2 study using ipilimumab, nivolumab, and trabectedin for previously untreated metastatic soft tissue sarcoma

11562

Background: Sarcoma cells are most immunogenic earlier in the disease course and before treatment when the immune system can recognize and destroy them. Hypothesis: Immune checkpoint inhibitors would be most effective when given to previously untreated patients with metastatic soft tissue sarcoma. Methods: Eligible patients for this Phase 2 study are previously untreated patients ≥ 18 years of age with unresectable or metastatic soft tissue sarcoma, with measurable disease by RECIST v1.1. Immune checkpoint inhibitors Ipilimumab (I) and Nivolumab (N) were given with Trabectedin (T), a marine derived alkaloid with defined doses of I (1 mg/kg i.v. q 12 weeks), N (3 mg/kg i.v. q 2 weeks), and T (1.2 mg/m2 i.v. q 3 weeks). Primary endpoints: (1) Objective response rate by RECIST v1.1 via CT scan or MRI, (2) Progression-free survival (PFS): from first day of treatment to disease progression or death due to any cause; otherwise, it is censored at the time of last follow-up, and (3) Overall survival: from first day of treatment to death due to any cause; otherwise, it is censored at the time of last follow-up. Results: There were eighty-two evaluable subjects, having completed the first cycle of I, N, and T and have had a CT or MRI scan at the 6-week follow-up period. Best Overall Response by RECIST v1.1 = 7 CR (2 surgical CR), 9 PR, 54 SD, and 12 PD. Disease control rate was 85.4%. The median PFS was >6.4 (range: 0-32) months; 6-month PFS rate: 57.3%. The median OS was >12.0 (0-38) months; 6-month OS rate: 78.8%. Safety analysis: The most common Grade 3 TRAEs include increased ALT (26), anemia (11), increased AST (9), and fatigue (8). Common Grade 4 TRAEs include thrombocytopenia (2), increased AST (2), increased ALT (2), and increased CPK (2). There was one Grade 5 TRAE of rhabdomyolysis (1). Conclusions: Taken together, these results suggest that first-line combinatorial therapy with I, N, and T are (1) synergistic, and (2) may be equal or superior to, and safer than, standard first line therapy for advanced/metastatic soft tissue sarcoma. Clinical trial information: NCT03138161.

First results of a randomized phase IB study comparing nivolumab/ipilimumab with or without CBM-588 in patients with metastatic renal cell carcinoma

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Background: Recent evidence suggests that the gut microbiome is a potent mediator of immune checkpoint inhibitor (ICI) activity in metastatic renal cell carcinoma (mRCC), with both specific bacterial species and cumulative microbial diversity driving response (Routy et al Science 2018; Salgia et al Eur Urol 2020). We examined whether the butyrate-producing bacterium Clostridium butyricum, the key constituent of CBM-588, could modulate the gut microbiome in patients (pts) with mRCC receiving nivolumab/ipilimumab (N/I) and secondarily improve clinical outcome. Methods: An open-label, randomized study was conducted, with key eligibility criteria including confirmed clear cell and/or sarcomatoid mRCC, intermediate/poor risk by IMDC criteria and no systemic therapy for metastatic disease. Patients were randomized 2:1 to receive either N/I+CBM-588 or N/I alone. N/I was dosed at 3 mg/kg and 1 mg/kg IV every 3 weeks for 12 weeks, followed by N at 480 mg IV every 4 weeks. CBM-588 was dosed orally at 80 mg bid. Stool was collected for bacteriomic profiling at baseline and 12 weeks. Metagenomic sequencing was employed using previously published methods (Dizman et al Cancer Med 2020). The primary endpoint of the study was change in Bifidobacterium spp. from baseline to week 12. Secondary endpoints included change in microbial diversity and clinical outcomes including response rate (RR) and progression-free survival (PFS). Results: 30 pts were randomized between April 2019 and Nov 2020; 1 pt was excluded after genomic sequencing clarified a diagnosis of sarcoma. Among 29 evaluable patients (21:8 M:F), median age was 66, 10 pts (34%) had sarcomatoid features and 24 pts (83%) were intermediate risk. Metagenomic sequencing of paired stool specimens showed an 8-fold increase in B. bifidum and a 6-fold increase in B. adolescentis in pts receiving N/I+CBM-588 from baseline to week 12. C. butyricum was detected only in pts receiving CBM-588. Pathogenic species (e.g., Escherichia. coli and Klebsiella spp.) were more prevalent in pts not receiving CBM-588. RR was significantly higher among pts receiving N/I+CBM-588 vs N/I alone (59% vs 11%; P = 0.024). Median PFS was also prolonged with the addition of CBM-588 to N/I (NR vs 11 weeks; P < 0.001). No significant difference in grade 3/4 toxicities were observed between study arms. Conclusions: This is the first randomized, prospective study to suggest enhancement of ICI response with a live bacterial product. The observed clinical impact is corroborated by biologic findings supporting gut modulation by CBM-588. Clinical trial information: NCT03829111.

A phase 2 study of talimogene laherparepvec, nivolumab, and trabectedin (TNT) in advanced sarcoma

11567

Background: Combination trabectidin (T) and nivolumab (N) has been shown to be a safe and effective therapy in soft tissue sarcoma (STS). Intratumoral injection of talimogene laherparepvec (TVEC) has a local oncolytic effect, and increases immune response via enhanced recruitment of antigen presenting cells, and thereby cytotoxic immune response. This study aims to determine if the addition of TVEC to combination trabectedin and nivolumab is effective and safe in advanced sarcoma. Methods: Eligible patients include patients ≥ 18 years of age with locally advanced unresectable or metastatic STS, measurable disease by RECIST v1.1, and at least one accessible tumor for TVEC intratumoral injection. N (3 mg/kg i.v. q 2 weeks), T (1.2 mg/m2 i.v. q 3 weeks) and TVEC (1x10e8 PFU/ml q 2 weeks depending on tumor size) were administered. A test dose of TVEC (1x10e6 PFU/ml) was initially given, followed three weeks later by full dose TVEC. Primary endpoint: Progression-free survival (PFS); Secondary endpoints: (1) Best overall response during treatment period, (2) PFS rate at 6 and 9 months, (3) Overall survival (OS) rate at 6, 9, and 12 months, (4) Incidence of conversion from unresectable to resectable tumor, and (5) Incidence of treatment-related adverse events. Interim. Results: There were 36 evaluable subjects under the Modified Intention-to-Treat (MITT) population, having completed the first cycle of TNT and a CT or MRI scan at the 6-week follow-up period. The most common histological subtypes include leiomyosarcoma (9), liposarcoma (5), spindle cell sarcoma (3), pleomorphic sarcoma (2), Ewing’s sarcoma (2), and other (5). Median number of prior lines of therapy was 4 (range 1-8). Best Overall Response by RECIST v1.1 = 3 PR, 27 SD, 5 PD. One patient, with previously unresectable disease was taken for resection and was found to have 100% necrosis on surgical pathology. Disease control rate (CR+PR+SD) was 86.1%. The median PFS was 5.5 (range: 1-18) months; 6-month PFS rate: 62.1%. Median PFS on therapy immediately preceding this trial was 2.0 months (range = 1-14 months). There were 47 evaluable subjects for OS analysis under the Intention-to-Treat (ITT) population having received at least one dose of T and N. The median OS was 9.0 (range 0-20) months; 6-month OS rate: 73%. Safety analysis: There were 47 evaluable subjects under the ITT population. 28% of these patients experienced ³1 SAE. The most common grade 3/4 TRAEs include anemia (12), increased ALT (8), fatigue (4), thrombocytopenia (4), neutropenia (4). There were no grade 3/4 TVEC injection site reactions. 22% of patients in the MITT cohort remain on study. Conclusions: These results suggest that combination therapy with TNT appears to be as effective as standard therapy, with no new safety signals seen. Furthermore, median PFS exceeded that of the immediately preceding lines of therapy in this heavily pre-treated cohort. As data matures, further data will be reported. Clinical trial information: NCT03886311.

Radiomic features of renal cell carcinoma primary and metastatic sites as predictors of TERT and BAP1 mutations

282

Background: TERT and BAP1 mutations are associated with poor clinical outcome in patients (pts) with metastatic renal cell carcinoma (mRCC) (Dizman et al JITC 2020; Joseph et al J Urol 2016). In this study we explore radiogenomics as a non-invasive method to identify these alterations. Methods: Pts with mRCC who had genomic testing in the course of routine clinical care were included in the current analysis. Pts were assessed with the GEM Extra assay, a CAP-accredited, CLIA-certified test encompassing paired tumor-normal whole exome sequencing (WES) and tumor whole transcriptome sequencing (TGen; Phoenix, AZ). Pts underwent CT imaging; radiomic analysis was performed on the segmented metastatic and primary lesions. Features were independently correlated with TERT and BAP1 mutation status to generate Pearson correlation values (PCVs). Results: 92 pts (65:27 M: F) were included in the analysis; of these, the majority of pts (84%) had clear cell histology. Alterations in the TERT gene were seen in 12 pts. In these pts 1,325 radiomic features of the primary tissue were examined and 251 features correlated with a PCV ≥ |0.2|. Of these, 42 features were correlated with a PCV ≥ |0.3|. Highest correlation with TERT mutation was seen with Gray Level Cooccurrence Matrix (GLCM) and First Order Features (FOF). 9 pts had BAP1 mutation with 5 detected in primary tumor and 4 in metastatic sites. Analysis of primary tumor imaging yielded no significant associations between radiomic features and BAP1 mutation. However, out of approximately 1,500 radiomic features noted in metastatic sites, 111 features correlated with BAP1 mutation with a PCV ≥ 0.2. Of these, 15 features correlated with a PCV ≥ 0.3. The radiomic features with the highest correlation with BAP1mt were Gray Level Dependence Matrix (GLDM) and GLCM. Conclusions: By identifying a correlation between radiomic features of TERT mutation in primary tumors and BAP1 mutation in metastatic sites, our work may ultimately yield a non-invasive method of discerning mutational status in patents with mRCC. Efforts are ongoing to validate our findings within The Cancer Imaging Archive.

Denosumab in advanced/unresectable giant-cell tumour of bone (GCTB): For how long?

BACKGROUND

Giant-cell tumours of bone (GCTB) are RANK/RANK-ligand (RANKL) positive, aggressive and progressive osteolytic tumours. Denosumab, a RANKL inhibitor, was FDA-approved for adults and skeletally mature adolescents with unresectable GCTB or when surgical resection is likely to result in severe morbidity. Data on long-term toxicity and activity of denosumab monthly 'GCTB-schedule' (120 mg per 12/year, 1440 mg total dose/year) are lacking.

METHODS

Patients with GCTB receiving denosumab, 120 mg on days 1, 8, 15, 29 and every 4 weeks thereafter, from 2006 to 2015 treated in two centres were included. Long-term toxicity was evaluated.

RESULTS

Ninety-seven patients were identified. 43 patients underwent resection of the tumour with a median time on denosumab treatment of 12 months (range 6-45 months). Fifty-four patients had unresectable GCTB's (male/female 23/31, median age 35 years [range: 13-76 years], 26% presented with lung metastases, 31% had primary tumor located to the spine, 63% were relapsed after previous surgery) with a median time on denosumab of 54 months (9-115 months). In the unresectable GCTB group, tumour control and clinical benefits were observed in all patients undergoing denosumab, whereas 40% of patients discontinuing denosumab had tumour progression after a median of 8 months (range 7-15 months).

ADVERSE EVENTS

Overall, six (6%) patients developed osteonecrosis of jaw (ONJ): 1/43 (2%) in the resectable group, 5/54 (9%) in the unresectable group, with a 5-year ONJ-free survival of 92% (95% CI 84-100). Only patients with prolonged treatment experienced mild peripheral neuropathy (6/54, 11%), skin rash (5/54, 9%), hypophosphataemia (2/54, 4%) and atypical femoral fracture (2/54, 4%).

CONCLUSIONS

Prolonged treatment with denosumab has sustained activity in GCTB, with a mild toxicity profile. The dose-dependent toxicity observed recommends a careful and strict monitoring of patients who need prolonged treatment. Decreased dose-intensity schedules should be further explored in unresectable GCTB.