Gao, Xin Yuan

The NCCN Guidelines for Prostate Cancer include recommendations for staging and risk assessment after a prostate cancer diagnosis and for the care of patients with localized, regional, recurrent, and metastatic disease. These NCCN Guidelines Insights summarize the panel's discussions for the 2024 update to the guidelines with regard to initial risk stratification, initial management of very-low-risk disease, and the treatment of nonmetastatic recurrence.

2561 Background: Some cancers, including breast, ovarian, pancreatic, and prostate cancers, are traditionally considered “cold” tumors, less likely to trigger an immune response and/or respond to immune checkpoint inhibitors (ICIs). However, some patients with these cancer types may benefit from ICIs. Here we investigate if a high blood tumor mutational burden (bTMB-H) may predict benefit to ICIs in such tumor types. Methods: We retrospectively queried the Guardant Health database for patients with advanced breast (n = 8531), ovarian (n = 1106), upper GI/pancreatic (n = 5110), and prostate (n = 7153) cancer who had ctDNA next-generation sequencing (Guardant360, Redwood City, CA) as part of routine clinical care from 2020-2022. Mutation profiles were evaluated for patients with bTMB-H (based on previously reported 80th percentiles for each tumor type, breast ≥15.31mut/Mb, ovarian ≥14.98mut/Mb, pancreatic ≥11.36mut/Mb, prostate ≥13.4mut/Mb) vs those with bTMB below this threshold (bTMB-L). A subset of cases were analyzed in a multi-institutional clinical cohort with a bTMB of ≥10mut/Mb (n = 35). Results: bTMB-H was observed in 9.5% of patients with breast cancer, 5.1% ovarian, 2.0% pancreatic, and 4.4% prostate. Genes more often mutated in patients with pTMB-H vs pTMB-L in each cancer type included TP53 and PIK3CA in breast cancer; TP53 and CHEK2 in ovarian; ATM and CHEK2 in pancreatic; TP53 and AR in prostate (all p values < 0.01). Patients in the clinical cohort (n = 35) had a median age of 74 (range: 40-85) 29/35 White / 4/35 Black, 27 prostate, 1 breast, 3 upper GI. Patients underwent first ctDNA analysis after a median of 3 (range 0-11) lines of therapy. The median bTMB detected was 16.59 mut/Mb (range: 10.02-152.85); six patients (6/35) were MSI-H. Twenty-three patients received ICI after a median of 6 (range: 0-8) lines of therapy, either alone (9, 39%) or in combination with hormonal therapy (5, 22%), chemotherapy (3, 13%) or targeted therapy (6, 26%). The median time to progression on ICI was 5.0 (95% CI, 3.6-6.4) months and median duration of response was 19.8 months (12.1-20.2). The ORR for evaluable patients was 13% and 74% of patients had progressed on therapy at time of data cut-off. Conclusions: "Cold” tumors represent a meaningful portion of patients with advanced cancer in which ICIs are not typically leveraged, and ctDNA was a feasible tool for identifying patients with bTMB-H who achieved durable responses from ICI-based therapy. The efficacy in this clinical cohort of traditionally “cold” tumors approaches other pan-cancer cohorts that include more traditionally immunoresponsive tumor types; further research is warranted to explore predictive value of bTMB, including potential tumor-specific thresholds, for optimizing patient selection for ICIs.

165 Background: A prior study of patients with advanced cancers treated with immune checkpoint inhibitors (ICI) associated improved overall survival with tissue tumor mutational burden above the 80th percentile in each histology (tTMB-H). TMB can also reliably be calculated via liquid biopsy (bTMB), and trends higher than tTMB in analogous tumors. Here, we generate a plasma-informed benchmark for bTMB-H in advanced prostate cancer and report preliminary data from an ongoing multi-institutional case series of patients treated with ICI. Methods: Circulating tumor DNA (ctDNA) next generation sequencing (NGS) results from 3,504 patients with advanced prostate cancer who received a Guardant360 liquid biopsy within a 12-month period were analyzed. The 80th percentile of TMB was defined as the benchmark for bTMB-H in this cohort, and prevalence of microsatellite instability (MSI-H) was determined. Subsequently, clinical data were collected from patients across five institutions who received pembrolizumab based on bTMB scores or other tumor characteristics (i.e. CDK12 mutation). Results: Overall, mean and median bTMB were calculated as 12.34 mut/Mb and 8.61 mut/Mb, respectively (range: 0 – 1164.75 mut/Mb). The 80th percentile of bTMB was 13.4 mut/Mb and the 90th percentile was 16.6 mut/Mb. 2.6% of patients were both MSI-H and bTMB-H. No patients with bTMB < 13.4 mut/Mb (TMB-L) were found to be MSI-H. Ten patients from five institutions received pembrolizumab (8 monotherapy) after a median of 4.5 lines of prior therapy (Table). Four patients were MSI-H. The 3 patients in the cohort with PSA decreases > 50% had both MSI-H and bTMB ≥ 13.4 mut/Mb. Per RECIST criteria, disease was controlled (CR, PR, SD) in 6 of 7 (86%) patients with bTMB scores ≥ 13.4 mut/Mb. Conclusions: These data continue to affirm that ctDNA NGS is a practical and cost-effective means of assessing potential predictors of ICI activity in patients with advanced prostate cancer. Preliminary data from this growing cohort of patients who have received ICI guided by bTMB scores and other molecular parameters identified via ctDNA NGS, including MSI-H, demonstrate a clinical benefit from therapy. Further studies are warranted for contextualizing individual tumor bTMB scores with established, pathology-specific benchmarks.[Table: see text]

TPS3161 Background: The p53 pathway has been implicated in antitumor immunity, including antigen presentation and T-cell proliferation. Loss of p53 function can increase resistance to immunotherapy across many tumor types. Eprenetapopt (eprenet) is a small molecule that stabilizes the folded structure of p53, resulting in activation of mutant p53 and stabilization of wild-type (WT) p53. It also targets the cellular redox homeostasis, resulting in induction of apoptosis in tumor cells. In vivo, mice carrying supernumerary copies of the TP53 gene harbor a pro-inflammatory tumor microenvironment, an effect recapitulated in TP53 normal-copy mice treated with eprenetapopt. Combining eprenetapopt and anti-PD1 or anti-CTLA4 therapy resulted in enhanced tumor growth inhibition and improved survival in TP53 WT mice inoculated with B16 melanoma and MC38 colon adenocarcinoma cells . Based on these results, we hypothesized that eprenet-induced p53 stabilization may augment response to immunotherapy. To test this hypothesis, we are conducting a phase 1b/2 study of eprenet in combination with pembrolizumab (eprenet+pembro) in pts with solid tumors. Methods: The primary objectives are to determine the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) and to assess the safety and tolerability of eprenet+pembro in pts with advanced solid tumors. The secondary objectives are to estimate the anti-tumor activity and to describe the pharmacokinetics of the combination. Exploratory objectives include assessing predictive and pharmacodynamic markers of response. The study includes a safety lead-in with a 3+3 dose de-escalation design for pts with advanced solid tumors with known tumor TP53 mutation status ( TP53 WT is acceptable) (max 18 pts), followed by expansion cohorts in pts with NSCLC, gastric/GEJ and urothelial cancer (max 100 pts). In expansion, pts with urothelial and gastric cancers must be naïve to anti-PD-1/ L1 therapy. Eprenet is given IV once daily on Days 1–4 while pembro is administered on Day 3 of each 21-day cycle. The RP2D of eprenet+pembro is considered the dose at which ≤ 1 of 6 pts in a cohort has a dose-limiting toxicity (DLT). Primary endpoints are occurrence of DLTs, adverse events (AEs) and serious AEs with eprenet+pembro. Key secondary endpoints are best objective response, progression free survival and overall survival. Exploratory endpoints include gene mutations by next generation sequencing (including TP53), mRNA expression, multiplex immunohistochemistry and transcriptomics, multiplex flow cytometry on peripheral blood mononuclear cells and cytokines in serum. Continuous monitoring of toxicity will be conducted. The trial opened in May 2020 and is actively enrolling patients. Clinical trial information: NCT04383938.

5077 Background: Several ICIs are used in first and subsequent lines of therapy for mRCC, either alone or in combination with another ICI or targeted therapy (TT). There are no data on the efficacy and safety of using an ICI in patients who have already received an ICI in a prior line of therapy. Methods: We reviewed patients with mRCC at 8 institutions who received 2 separate lines of ICI therapy (ICI-1, ICI-2), including as a single-agent and/or combination with other agents. The primary outcomes were overall response rate (ORR) and time to progression (TTP) with ICI-1 and ICI-2. Immune-related adverse events (irAEs) were graded using CTCAEv5.0. Results: 65 patients were included. Median age at diagnosis of mRCC was 60 years (range 30-86) and the majority had clear cell RCC (n=56, 86%). Median follow-up was 3.5 years (95% CI 2.9-4.4). Median lines at which ICI-1 and ICI-2 were received were 1 (1-6) and 3 (2-8) respectively. Reasons for discontinuing ICI-1 were disease progression (n=47, 72%), toxicity (n=15, 23%) or other (n=3, 5%). Therapies received at ICI-2 were single-agent ICI (n=26, 40%), or combinations of ICI with another ICI (n=20, 31%), TT (n=11, 17%) or other agent (n=8, 12%). Responses to ICI-1 and ICI-2 are shown in the Table; ORR to ICI-2 was significantly lower than to ICI-1 (23% vs. 36%, p=0.044). Amongst those who responded to ICI-2 (n=14), 7 (50%) received single-agent ICI, and the remainder received ICI in combination with another ICI (n=4, 29%) or TT (n=3, 21%); 7 patients (50%) had previously responded to ICI-1. The ORR to ICI-2 was higher in responders to ICI-1 (32%) compared to those with SD (17%) or PD (15%) to ICI-1. Median TTP (mTTP) at ICI-2 was shorter compared to ICI-1 (5.3 months vs. 8.5 months, Wilcoxon p=0.024). 29 patients (45%) experienced an irAE with ICI-2; 8 (12%) and 3 (5%) had a grade 3 or 4 irAE respectively, with 3 (30%) of these patients having previously had ≥grade 3 irAE to ICI-1. There were no treatment-related deaths. Conclusions: The ORR to ICI-2 was 23%, which is comparable to that seen with ICI after prior TT. Responses were seen even amongst those receiving single-agent ICI at ICI-2 and the likelihood of response to ICI-2 was higher if a patient had previously responded to ICI-1. No increase in toxicity with ICI-2 was apparent. Additional data from prospective studies are needed to determine whether sequential ICI has a role in treatment of mRCC. [Table: see text]