Citations

TPS4616 Background: Osseous metastases (OM) occur in approximately 30% patients with advanced RCC. Despite therapeutic advances, OM are associated with poor survival and risk of symptomatic skeletal events (SSEs). Cabozantinib targets multiple tyrosine kinases, including vascular endothelial growth factor (VEGF) receptors and MET (Mesenchymal-Epithelial Transition factor), which are overexpressed in OM, contributing to cabozantinib’s enhanced bone activity. Radium-223, an alpha-emitting bone-seeking radioisotope, prolongs survival in men with metastatic castration-resistant prostate cancer to the bone. Building on this therapeutic approach targeting OM, our pilot study of radium-223 with VEGF inhibition in RCC with OM has also shown safety, improvement in circulating bone turnover markers, and early efficacy (McKay et al, CCR 2018). To address the unmet need to improve SSE rates and outcomes in RCC and OM, we designed a study investigating cabozantinib with or without radium-223 in patients with RCC with OM (NCT04071223). Methods: This is an open-label, multicenter randomized phase-2 study. Key inclusion criteria include metastatic RCC of any histology with ≥1 OM, at least 1 OM without prior radiation, any number of prior therapies, and Karnofsky performance status ≥ 60%. Use of a bone protecting agent is required unless contraindicated. Patients are randomized 1:1 to cabozantinib with (Arm A) or without (Arm B) radium-223. The starting dose of cabozantinib for Arm A is 40 mg by mouth daily to be escalated to 60 mg daily after cycle 1 (1 cycle = 28 days) if no persistent grade 2 or grade ≥3 toxicity. Radium-223 is administered at a fixed dose of 1.49 microcurie/kg IV every 28 days x 6 doses. The starting dose for cabozantinib in Arm B is 60 mg daily. The primary endpoint is SSE-free survival. Secondary endpoints include safety, progression-free survival, overall survival, time to first SSE, objective response rate, time to subsequent anti-cancer therapies, quality of life (QoL) measures, and correlative analyses including liquid biopsy and tumor tissue analysis. The study is designed to have 85% power to detect an improvement in 6-month SSE-free survival rate from 65% to 78% with one-sided α = 0.05 significance. To ensure 124 evaluable patients, target accrual is 134 (67 per arm). The group-sequential design includes a safety run-in and an interim analysis for futility when 50% of the expected number of events have been observed. The safety run-in, performed in the first 12 patients randomized to combination therapy, did not demonstrate dose limiting toxicities. Final data analysis will occur when 99 events have been observed. The study was activated in July 2020 and accrual is ongoing throughout the National Clinical Trials Network (NCTN). Continued site participation and enrollment are essential to evaluate this therapeutic strategy. Clinical trial information: NCT04071223 .

9578 Background: Anti-PD1 immunotherapy has shown improved clinical outcomes in patients (pts) with advanced cSCC, and recently, in the neoadjuvant setting for resectable disease. Pathological (path) response is predictive of recurrence in melanoma and recent NeoIT trials suggests the same in cSCC; however, an analysis of clinical outcomes in pts with resectable cSCC treated with intended anti-PD1-based NeoIT in larger datasets remains unknown. Methods: Pts with resectable cSCC treated with intended anti-PD1-based NeoIT from 17 cancer centres globally were included. Baseline patient and disease characteristics, treatment regimen, path response and recurrence-free survival (RFS) or progression-free survival (PFS) were collected and examined. Results: 134 pts with resectable cSCC were treated with intended anti-PD1-based NeoIT. Median age was 75 years old (range, 39-97), 72% (n=97) were male. One fifth (22%, n=29) were immunocompromised and 43% (n=58) had ECOG PS of ≥1. Of 125 (93%) pts with known primary cSCC, 82% (n=102) were from the head & neck. Most pts (79%, n=106) were stage III/IV. The majority had anti-PD1 monotherapy (91%, n=122) and 9% (n=12) had anti-PD1+/-investigational agent. Median follow-up from commencement of NeoIT was 10 months (95% CI, 9 - 12). Nearly half of the pts (49%, n=66) underwent surgery; 37 (56%) pts had major pathological response (MPR; ≤10% viable tumour cells at the surgical specimen; 31 [47%] had complete path response [0% of viable tumour cells] and 6 [9%] had near complete path response [1-10% of viable tumour cells]), 6 (9%) had partial path response (pPR; >10% and ≤50% of viable tumour cells), and 23 (35%) had path non-response (pNR; >50% of viable tumour cells). Of the 66 pts who underwent surgery, 11% (n=7) had recurrence (5 loco-regional and 2 distant recurrence), all non-MPR pts (1 pPR and 6 pNR). 12-months RFS was improved with MPR vs non-MPR (100% vs 79%, p=0.004). 52% (n=34) pts had adjuvant treatment (23 anti-PD1 alone, 7 anti-PD1+/-investigational agent, 2 platinum and 2 cetuximab). Within non-MPR pts, 12 had adjuvant treatment (3 recurred; 25%), while 17 did not have adjuvant treatment (4 recurred; 24%). Fifty-one percent (n=68) of pts did not have surgery; 9 (13%) due to progressive disease (PD) and 53 (78%) due to clinical response. Of the 53 pts with a clinical response, 5 (9%) subsequently progressed. Fourteen (10%) pts have died, 6 (4%) related to cSCC; 2 had surgery (non-MPR) and 4 did not have surgery (all due to PD). Conclusions: Anti-PD1-based NeoIT is an active regimen in resectable stage II-IV cSCC and is associated with high clinical response and MPR rates. No pts with MPR from NeoIT has recurred to date, however, 9% of pts who did not have surgery due to clinical response eventually progressed. These findings highlight the importance of further research to investigate the role of surgery in this subgroup of patients.

9503 Background: Neoadjuvant ± adjuvant immunotherapy improves event-free survival relative to adjuvant immunotherapy alone for patients with high-risk resectable stage III melanoma. However, the optimal regimen balancing efficacy and tolerability is not known. T-cell immunoglobulin and ITIM domain (TIGIT) is a promising immune checkpoint but its therapeutic potential in stage III melanoma is underexplored. Methods: In this phase II trial, patients with resectable, macroscopic stage III melanoma received four 21-day neoadjuvant cycles of 1200mg IV atezolizumab (atezo, anti-PD-L1) + 600mg IV tiragolumab (tira, anti-TIGIT), followed by therapeutic lymph node dissection (TLND) and eight 21-day adjuvant cycles of 1200mg IV atezo. Primary endpoints were pathologic response (of all patients initiating neoadjuvant therapy) and recurrence-free survival (RFS) from the time of TLND in patients who were operated on per protocol and received adjuvant therapy. Secondary endpoint was adverse events (AEs); exploratory endpoints included event-free survival (EFS) and distant metastasis-free survival (DMFS). Results: Thirty-four patients, median age 59 years, were accrued and initiated neoadjuvant atezo/tira. 76.5% had >1 metastatic lymph node involved at baseline and 73.5% presented with Stage IIIC disease. All 34 patients were evaluable for AEs, pathologic response and EFS. Four patients were diagnosed with metastatic disease during neoadjuvant treatment, while 30 had TLND per protocol and 28 received adjuvant treatment and were evaluable for RFS and DMFS. Major pathologic responses (MPR, ≤10% viable tumor) were observed in 16/34 patients (47.1%, Table). With 19.9 months median follow-up from registration, 12-month EFS was 72.0% (95% CI 57.9 to 89.5%). With 16 months median follow-up from operation, 12-month RFS was 73.3% (n=28, 95% CI 56.9 to 94.5%), while 12-month DMFS was 86.0% (n=28, 95% CI 72.2 to 100%). In the 16 patients with an MPR, 2 did not receive adjuvant treatment and were followed for 33.3 and 10.8 months without recurrence/death. In the remaining 14 patients, 12-month RFS and 12-month DMFS were both 91.7% (95% CI 77.3 to 100%). 5 patients (14.7%) experienced any grade 3+ AE with 2 (5.9%) at least possibly related to the neoadjuvant regimen. Conclusions: Among patients with high-risk resectable stage III melanoma, neoadjuvant atezo/tira was a promising regimen with a favorable safety profile and warrants further study. Identification of predictive biomarkers will allow for optimization of neoadjuvant therapy for individual patients. Clinical trial information: NCT03554083 . Pathologic response. N=34 Major Pathologic Response 16 (47.1%) Pathologic complete response (no viable tumor) 13 (38.2%) Near-pathologic complete response (0.1−10% viable tumor) 3 (8.8%) Pathologic partial response (>10.0−50% viable tumor) 2 (5.9%) Pathologic non-response (>50% viable tumor) 12 (35.3%) No per protocol operation 4 (11.8%)

2085 Background: Primary Central Nervous System Lymphoma (PCNSL) is a rare and aggressive non-Hodgkin lymphoma with no approved treatments for relapsed/refractory (R/R) patients, representing a critical unmet need. MyD88 mutations in ~70% of PCNSL patients drive Interleukin-1 receptor associated kinase 4 (IRAK4) activation, promoting NF-κB signaling, inflammation, and tumor progression. Emavusertib, a potent oral IRAK4 inhibitor, crosses the blood-brain barrier and shows preclinical synergy with Bruton tyrosine kinase inhibitors (BTKi), re-sensitizing BTKi-resistant cell lines. This study evaluates the molecular and pharmacokinetic (PK) data associated with responses to emavusertib + ibrutinib combination therapy in R/R PCNSL patients. Methods: The safety, clinical activity, and potential biomarkers of emavusertib in R/R PCNSL are being investigated in the ongoing open-label, Phase 1/2 TakeAim Lymphoma trial (NCT03328078). Pre-dose and 1.5-hour post-dose plasma samples were collected on Cycle 3 Day 1, Cycle 5 Day 1 and Cycle 7 Day 1. Cerebrospinal fluid (CSF) samples were obtained via a lumbar puncture within 1.5 hrs of collection of the post-dose plasma PK sample on Cycle 3 Day 1. Mutation analysis was based on patients’ molecular pathology reports provided by trial sites. Sequencing of archival tissues, CSF and plasma are in progress. Results: As of 06 December 2024, CSF concentration data were available for 7 PCNSL patients. The mean emavusertib concentration in CSF was 81.3 ng/ml (54.7-104.0) in patients receiving 100 mg emavusertib BID (n = 4). In patients receiving 200 mg emavusertib BID (n = 3), the mean emavusertib concentration in CSF was higher at 175.7 ng/ml (114.8-209.4), which is 2.2X the mean value in patients who received 100 mg emavusertib BID (p-value = 0.02). All 7 patients received 560 mg ibrutinib QD, and the ibrutinib concentrations in the CSF were consistent with findings from previously published clinical studies. MyD88 mutation status was available for 7 patients of which all had prior exposure to BTKi regimens. Among these, 6 patients had MyD88 mutation of which 4 patients had responded (3 complete responses and 1 partial response) to emavusertib + ibrutinib combination with duration of response (DOR) up to 18.9 months with data collection ongoing. Conclusions: Preliminary CNS pharmacokinetic data demonstrates that emavusertib concentration in CSF increases with increasing emavusertib dose. Patients with MyD88 mutations showed expected promising preliminary efficacy to emavusertib + ibrutinib combination and may overcome BTKi resistance. Enrollment in this trial is ongoing. Clinical trial information: NCT03328078 .

TPS4632 Background: There is currently no Food and Drug Administration (FDA)-approved treatment for intermediate-risk non–muscle-invasive bladder cancer (IR NMIBC), defined as recurrence of low-grade (LG) Ta within 1 year, solitary LG Ta > 3 cm, multifocal LG Ta, high-grade (HG) Ta (≤3 cm), and/or LG T1. Nadofaragene firadenovec-vncg is the first FDA-approved intravesical nonreplicating gene therapy for treating high-risk BCG-unresponsive NMIBC with carcinoma in situ (CIS) ± papillary tumors. In a nonrandomized, multicenter, open-label, repeat-dose, phase 3 study, 53.4% of participants (55/103) with CIS ± HG Ta/T1 achieved complete response 3 months after the first instillation. Nadofaragene firadenovec was well tolerated, with no grade 4/5 study drug-related AEs. Because maintenance treatment with nadofaragene firadenovec following tumor resection may improve clinical outcomes in patients with IR NMIBC, the ABLE-32 open-label randomized study is being conducted to evaluate the efficacy of nadofaragene firadenovec administered every 3 months versus observation in participants with IR NMIBC. Methods: This phase 3 study includes approximately 100 global sites with 454 anticipated participants. Adults aged ≥18 years, diagnosed with new or recurrent IR NMIBC, and having undergone transurethral resection of bladder tumor within 60 days prior to randomization are eligible. Participants will be randomly assigned 1:1 to receive nadofaragene firadenovec or continue observation. The nadofaragene firadenovec group will receive quarterly doses unless disease recurs or progresses. The observation group will be followed quarterly and may receive nadofaragene firadenovec if IR NMIBC recurs within 24 months. All participants will be evaluated for recurrence and progression using cytology, cystoscopy, and for-cause biopsy for up to 5 years. The primary endpoint is recurrence-free survival (RFS), from randomization to first documented recurrence, progression, or death. Secondary endpoints include RFS at 12 and 24 months and safety. Exploratory endpoints include effect on potential biomarkers and health-related quality of life. Final results are expected in 2031. Clinical trial information: NCT06510374 .

TPS4630 Background: Bacillus Calmette-Guérin (BCG) is the standard first-line therapy for patients with high-risk non–muscle-invasive bladder cancer (NMIBC) with carcinoma in situ (CIS) ± papillary tumors; however, patients whose disease is unresponsive to BCG therapy are unlikely to benefit from further courses of BCG. Bladder-preserving treatment options for patients with BCG-unresponsive NMIBC with CIS ± Ta/T1 include intravesical gene therapy (nadofaragene firadenovec-vncg), intravesical chemotherapy (gemcitabine and docetaxel), and immunotherapy (intravenous pembrolizumab and intravesical nogapendekin alfa inbakicept-pmln). In a pivotal phase 3 study, 53.4% of participants (55/103) with BCG-unresponsive NMIBC with CIS ± Ta/T1 achieved a complete response (CR) within 3 months of a single instillation of nadofaragene firadenovec, and of them, 45.5% (25/55) maintained a CR at 12 months. Nadofaragene firadenovec in combination with chemotherapy or immunotherapy may further improve clinical efficacy. ABLE-22 (NCT06545955) is an interventional study evaluating the safety and efficacy of nadofaragene firadenovec alone or in combination with chemotherapy (gemcitabine and docetaxel) or immunotherapy (pembrolizumab) in participants with high-risk BCG-unresponsive NMIBC. Participants not responding at month 3 will be offered reinduction. Methods: ABLE-22 will include approximately 40 to 75 sites across the United States and Canada; sites in Asia, Australia, and Europe may be included. Participants (anticipated N = 150) will be randomly assigned 1:1:1 to receive nadofaragene firadenovec (n = 50), nadofaragene firadenovec plus gemcitabine and docetaxel (n = 50), or nadofaragene firadenovec plus pembrolizumab (n = 50). Adults aged ≥18 years with documented NMIBC with CIS ± Ta/T1 that is unresponsive to ≥2 courses of BCG therapy within the last 12 months are eligible to enroll. The primary endpoint is CR (defined as absence of low- and high-grade NMIBC) at months 3 or 6, as participants with persistent NMIBC (any CIS, low-grade Ta, and > 3 cm or multifocal high-grade Ta) will be offered reinduction once, at month 3. Secondary endpoints include durability of CR, incidence of muscle-invasive progression, cystectomy-free survival, pathologic staging, overall survival, and safety. Durability of CR will be followed up to month 36 (assessed quarterly for the first 24 months); all other secondary endpoints will be assessed up to and including month 36. Exploratory endpoints include changes in expression of potential biomarkers in blood and urine. Results from this investigational, randomized, multicenter, open-label study evaluating the safety and efficacy of nadofaragene firadenovec alone or in combination with chemotherapy or immunotherapy are expected July 2028. Clinical trial information: NCT06545955 .

e22572 Background: Pancreatic cancer is a highly lethal malignancy that disproportionately impacts older populations, contributing significantly to global disease burden. Disability-adjusted life years (DALY) serve as a comprehensive metric to quantify the combined impact of mortality and morbidity. This analysis of the Global Burden of Disease Study-2021 (GBD-2021) aims to characterize trends in DALY rates attributable to pancreatic cancer among individuals aged 70 years and older across 204 nations. Methods: Data on DALY associated with pancreatic cancer for individuals aged 70+ were extracted for 204 nations from the GBD-2021 study for the years 1990 and 2021. Estimated annual percent change (EAPC) with 95% confidence intervals (CI) were calculated from 1990 to 2021. Results: The DALY rates were accessed among individuals aged 75 and older diagnosed with pancreatic cancer. In 1990, Greenland exhibited the highest DALY rate globally (2825.65), but by 2021, this position was surpassed by the United Arab Emirates (2775.52), with Greenland declining to the second-highest rate (2082.43). On the other hand, Turkmenistan had the lowest DALY rates in 1990, but by 2021, Mozambique had taken this position, with Turkmenistan ranking 170th. Despite the observed DALY rates from 1990 to 2021, Turkmenistan experienced the highest change (EAPC: 15.23, 95% CI: 10.88–21.18), followed by the Republic of Cabo Verde (EAPC: 12.88, 95% CI: 8.14–18.75) and Mongolia (EAPC: 4.53, 95% CI: 2.90–6.88). A decrease in DALY was observed in over 24 nations, with the Republic of San Marino recording the largest decline (EAPC: -0.37, 95% CI: -0.55, -0.12), followed by Bermuda (EAPC: -0.26, 95% CI: -0.43, 0.03) and Greenland (EAPC: -0.26, 95% CI: -0.45, -0.009). Conclusions: From 1990 to 2021, DALY rates related to pancreatic cancer among individuals aged 70 and older rose worldwide, particularly in Turkmenistan, the Republic of Cabo Verde, and Mongolia. There is a pressing need for global adoption of screening programs to enable early detection and treatment of these cases. Metric Region 1990 2021 EAPC with 95% CI (1990-2021) HIGHEST DISABILITY-ADJUSTED LIFE YEARS (DALYS) PERCENT CHANGE Turkmenistan 19.66 319.09 15.22 (10.88–21.18) Republic of Cabo Verde 98.12 1361.76 12.88 (8.14–18.75) Mongolia 172.14 952.05 4.53 (2.90–6.88) LOWEST DISABILITY-ADJUSTED LIFE YEARS (DALYS) PERCENT CHANGE Republic of San Marino 1323.96 834.01 -0.37 (-0.55, -0.12) Bermuda 1696.97 1249.11 -0.26 (-0.43, 0.03) Greenland 2825.66 2082.43 -0.26 (-0.45, -0.009)

e22570 Background: Aging into the seventh decade of life marks a pivotal shift in cancer susceptibility, with pancreatic cancer (PC) emerging as one of the most relentless threats to global health. This study utilizes three decades of Global Burden of Disease (GBD) data to unravel unprecedented insights into the prevalence and incidence of PC among adults aged 70 and older. Methods: We analyzed data from the GBD study to assess the temporal trends in the incidence and prevalence of PC from 1990 to 2021. The Annual Percentage Change (APC) and Average Annual Percentage Change (AAPC), along with 95% confidence intervals (CI), were utilized to assess the overall trends, with statistical significance evaluated using p-values. Results: Over the past three decades, the global burden of PC has surged significantly. In 1990, the global incidence of PC stood at 45.12 per 100,000, escalating to 54.47 per 100,000 by 2021. Likewise, global prevalence increased from 30.33 per 100,000 in 1990 to 40.60 per 100,000 in 2021, with incidence rates consistently exceeding prevalence, suggesting an accelerating number of new cases of PC worldwide. The AAPC analysis revealed a significant upward trajectory in both global incidence (AAPC: 0.6085, 95% CI: 0.5801, 0.6273 p < 0.000001) and prevalence (AAPC: 0.9467, 95% CI: 0.9188, 0.9659 p < 0.000001) of PC. Following the APC analysis, several notable trends emerged. The global incidence of PC experienced its most substantial increase between 2003 and 2010 (APC: 1.0806, 95% CI: 0.9817, 1.3206 p < 0.000001), while the slowest growth in incidence occurred from 1990 to 2003 (APC: 95% CI: 0.9817, 1.3206 p = 0.000400). Conversely, the global prevalence of pancreatic cancer saw its most pronounced rise between 1998 and 2001 (APC: 2.0389, 95% CI: 1.2005, 2.1962 p < 0.000001), with the slowest increase occurring from 1994 to 1998 (APC: 0.4632, 95% CI: 0.2544, 1.9767 p = 0.001200). Conclusions: The persistent rise in both incidence and prevalence of PC over the past three decades underscores a critical global health challenge, with a marked acceleration in recent years. These findings highlight the urgent need for targeted interventions and a deeper understanding of the factors driving this expanding burden, particularly as the incidence consistently outpaces prevalence. Metric Overall 1990 2021 AAPC with 95% CI (1990-2021) INCIDENCE RATES PER 100,000 Global Incidence 45.12 54.47 0.61 (0.58, 0.63) PREVALENCE RATES PER 100,000 Global Prevalence 30.33 40.60 0.95 (0.92, 0.97)

2072 Background: Methylation of the MGMT gene promoter (MGMTp) is a critical biomarker to inform GBM prognosis and guide treatment decisions, including clinical trial eligibility. Rapid reporting of MGMTp methylation can help stratify patients early and facilitate clinical trial referral during the crucial post-operative period where treatment options are being considered by patients and physicians alike. Methods: We developed a probe-based ddPCR method to detect and quantify MGMTp methylation. Assay specificity was assessed using bisulfite-converted, unmethylated DNA. Assay linearity and Limit of Detection (LoD) were determined using MGMTp methylated cell line DNA samples of decreasing fractional abundances (35%, 5%, and 0.5%) and decreasing DNA inputs (30ng, 10ng, 3ng,1ng and 0.5ng). The limit of Blank (LoB) was calculated using 16 replicates of unmethylated bisulfite-converted PBMC DNA, and DNA from tonsil FFPE samples (n = 9). Reproducibility studies were conducted on two different days with two different operators. Accuracy and concordance were assessed using an in-house MGMTp methylation pyrosequencing assay as an orthogonal method to analyze11 melanoma and one glioblastoma cell line. Preliminary clinical validation was conducted via analysis of FFPE tumor DNA from 34 GBM patients with clinical MGMTp methylation pyrosequencing results. Results: The MGMTp methylation ddPCR assay demonstrated 100% specificity to detect promoter methylation. The method linearly quantified both total DNA and methylated DNA along a range of input DNAs with conserved fractional abundances. The LoB was 0.036% and 0.034% using PBMC and tonsil FFPE DNA, respectively. The LoD was 0.075%. The bisulfite conversion and assay were highly reproducible, with a coefficient of variation < 20%. Among the 12 cell lines analyzed by both pyrosequencing and ddPCR the concordance was 100%. Ten of 11 GBM tumor samples identified as MGMTp methylated by the clinical pyrosequencing assay were also identified as methylated by the ddPCR assay. Five of 23 clinically unmethylated tumors were positive in the ddPCR assay with generally very low fractional abundances (0.08%, 0.12% 0.3%, 0.97% and 10.11%). Conclusions: We report preliminary validation of a highly sensitive and specific ddPCR assay to detect MGMTp methylation. Given the minimal sample requirements and rapid turnaround time for ddPCR assays, this test could eventually be utilized in clinical laboratories to quickly report MGMTp methylation status for GBM patient management.

2053 Background: Recurrent gliomas are highly aggressive brain tumors, often resistant to conventional treatments. Immune checkpoint inhibitors (ICI) have emerged as promising therapeutic agents by targeting tumor cells through immune modulation. However, clinical trials have demonstrated limited efficacy in recurrent gliomas. This study aimed to identify potential factors influencing treatment efficacy of ICIs in recurrent gliomas. Methods: This retrospective study, conducted across the Mayo Clinic following IRB approval, included patients ≥ 18 years diagnosed with adult-type diffuse gliomas. Eligible patients received treatment with at least 2 cycles of ICI for recurrent glioma between 2014 – 2024. Patients treated with ICIs as initial therapy were excluded. Clinical, radiographic, histological, and molecular data were analyzed, with missing information excluded. Responders to ICI were defined as patients who did not meet iRANO criteria for progressive disease based on first radiographic response assessment (and confirmatory follow up imaging as needed for possible pseudo-progression). Survival outcomes [Progression-Free Survival (PFS) and Overall Survival (OS)] and potential predictive variables were analyzed using the Kaplan-Meier method and Cox-Regression Analyses. Results: 67 patients met eligibility criteria (mean age: 45.1 ± 15.0 years; 64.2% male; 94% white). 64 (95.5%) patients received Pembrolizumab, 2 (3%) Nivolumab, and 1(1.5%) combined Ipilimumab/Nivolumab, with a median treatment duration of 2.77 (1.39 – 19.4) months. All had prior alkylating chemotherapy. The OS (from diagnosis) for IDH wildtype (IDH-WT, n = 36), IDH mutant, 1p/19q non-co-deleted (IDH-MUT, n = 17) and IDH mutant, 1p/19q co-deleted (OLIGO, n = 14) gliomas were 3.1, 9.2, and 18.6 years, respectively. The median PFS from time of ICI was 2.23 (0.69 – 27.3) months. 24 (36.9%) patients were identified as Responders. PFS was not significantly different between patients with IDH-MUT and IDH-WT gliomas (2.30 vs 2.07 months, p = 0.593). However, patients with OLIGO gliomas had a significantly higher PFS compared to IDH-WT gliomas (5.16 vs 2.07 months, p = 0.021). The proportion of responders was greatest in OLIGO gliomas, however, did not reach statistical significance (IDH-WT, 31.4%; IDH-MUT, 29.4%; OLIGO, 61.5%, p = 0.120). Overall PFS was not impacted by patient age, sex, and extent of initial resection. When analyses were limited to Responders, the PFS for IDH-WT, IDH-MUT and OLIGO gliomas were 5.75, 7.01 and 10.8 months, respectively ( p = 0.434). Conclusions: Patients with recurrent OLIGO gliomas may have a longer PFS with ICI therapy compared with recurrent IDH-WT and IDH-MUT gliomas. However, there is significant variability in ICI treatment efficacy between patients. Further molecular profiling is in progress to evaluate additional predictive biomarkers of response.