Citations

Abstract Introduction: Therapeutic outcomes in B-cell non-Hodgkin’s lymphoma (B-NHL) have substantially improved with the introduction of chimeric antigen receptor T-cell (CAR-T) therapy. Yet, persistent immune dysfunction and underlying metabolic dysregulation remain major obstacles to achieving durable clinical responses in B-NHL. We hypothesize that mitochondrial pathways play a critical role in mediating anti-tumor immunity during CAR-T therapy. Methods: Peripheral blood mononuclear cells were collected from healthy controls (CNTRL, n=5) and patients with advanced stage lymphoma (LYM) who received FDA approved CAR-T (n=32). Samples were collected before lymphodepletion (BL), at peak CAR-T expansion (PK) and one-month post-infusion (M1). Single-cell RNA sequencing was used to interrogate differential mitochondrial gene expression. Samples were obtained from LYM patients with complete remission for >6 months (CR), primary refractory (PD1), or relapsed (PD2) disease. Results: Compared to CNTRLs, LYM patients exhibited reduced expression of cytochrome c oxidase. At BL, CR patients demonstrated broader mitochondrial differential gene expression across all T-cell subsets relative to PD1 and PD2 and showed higher expression of MT-ATP-6, MT-ATP-8, and MT-CO3. Following CAR-T infusion, global mitochondrial gene expression increased across patients corresponding with expansion of CD8 effector T cells (Tem tumor circulating) and activated peripheral memory T cells (Tpm). Certain mitochondrial genes, such as MT-CO1, were durably expressed across LYM patients at BL, PK, and M1 in peripheral and central memory T cells (Tpm, Tcm). At PK, cytochrome c oxidase and ATP synthase genes were upregulated in CR Tpm and Tcm. At M1, MT-ATP-6, MT-ATP-8, MT-CO3 were significantly upregulated in CD8 memory precursor effector T-cells (MPECs) of CR patients compared to both PD1 and PD2. While CR and PD2 patients appeared clinically responsive at M1, CR samples maintained significantly higher MT-ATP-8 expression across T cell subsets (CD8 MPECS, Tpm, Tcm) compared to PD2 (p values 0.008; <0.0001; <0.0001). Conclusions: We report a temporal shift in immunometabolism with CAR-T therapy in LYM. Clinical responders exhibited sustained mitochondrial activity characterized by persistent expression of ATP synthase in CD8 MPECs and cytochrome c oxidase in Tpm and Tcm. In sum, mitochondrial programming may distinguish effective versus dysfunctional T cells and identify targets for therapeutic development. Citation Format: Jacqueline Turner, Panwen Wang, Patrizia Mondello, Melinda Tan, Christoph Schaefers, Chen Wu, Andre de Menezes Silva Corraes, Kevin Regan, Zuoyi Shao, Ma Audrey, Arushi Khurana, Nora N. Benanni, Yucai Wang, Paul Hampel, Saad J. Kenderian, Jonas Paludo, Urshila Durani, Patrick B. Johnston, Jose Caetano Villasboas, Stephen M. Ansell, Haidong Dong, Ying Li, Zeng Hu, Yi Lin. Mitochondrial transcriptome profiles associated with clinical responses to CAR-T therapy in aggressive lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 1213.

Abstract Cellular senescence is a dynamic, multistage biological program that exerts context-dependent effects on tumor initiation, progression, and overall carcinogenesis. Our laboratory has previously demonstrated that the early accumulation of p16Ink4a-expressing (representing strong cyclin-dependent kinase inhibition) senescent alveolar macrophages during tumorigenesis actively facilitates tumor formation and progression by inhibiting the infiltration of cytotoxic T lymphocytes. However, considering the dynamic nature of cellular senescence, distinct senescent cell populations could express high amounts of the alternative cell cycle inhibitor p21Waf1/Cip1 independently of p16Ink4a to potentially catalyze distinct functions. To test this, we have employed transgenic p21-ATTAC (p21-driven apoptosis through targeted activation of caspase 8) mice to investigate the role of p21-expressing cells during Kras-driven adenoma formation. In agreement with our previous observations following clearance of p16-expressing senescent cells, we found that removal of p21+ cells attenuates early tumor development. Western blot and immunofluorescence analyses corroborates a reduction in p21, p16, and multiple members of a putative senescence-associated secretory phenotype (SASP). Although senescent alveolar macrophages remain a critical therapeutic target, here we found that senescent endothelial cells also exhibited elevated expression of p21, p16, and SASP with a high senolytic response. Future studies will include identifying the predominant p21-expressing senescent endothelial subpopulations and elucidating the mechanisms by which endothelial senescence contributes to lung tumorigenesis. Collectively, our findings have unveiled additional senescent cell populations with the potential to drive lung tumorigenesis. Citation Format: Yuanning Du, Luis I. Prieto, Karthikbabu Jeganathan, Cheng Zhang, Hu Li, Darren Baker. Elucidating the role of p21 + senescent cells in early-stage lung tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 2268.

Abstract Prostate-specific membrane antigen (PSMA) is highly expressed in tumor-associated neovasculature in hepatocellular carcinoma (HCC), highlighting its promise as a theranostic target. This prospective study aimed to evaluate the utility of novel biomarkers derived from PSMA positron emission tomography computed tomography (PET/CT) to assess treatment response in advanced HCC patients (pts) receiving first line immune checkpoint inhibitors (ICI). Methods: This study (NCT05176223) enrolled unresectable, advanced HCC pts eligible for first-line ICI (atezolizumab/bevacizumab [A/B] or durvalumab/tremelimumab [D/T]) with measurable disease according to RECIST criteria. Primary endpoints: progression-free survival (PFS) per RECIST 1.1 and mRECIST; overall survival (OS); and best overall response. The survival distribution was estimated using the Kaplan-Meier method. Observed agreement is defined as the proportion of pts whose responses, as classified by PET/CT or CT, were concordant. Weighted kappa and Cohen’s kappa were used to quantify the strength of agreement between PET/CT and CT. Pts completed up to five 68Ga-PSMA PET/CT scans and blood collections. Results: Twenty-six pts were enrolled (25 evaluable) between Oct 2022 and Nov 2024. Median follow up was 22.1 months (m) (Q1, Q3: 14.5-23.7). Median age 68 yrs, 72% male, 88% White, 68% Child-Pugh [CP] A, 32% CP B, 32% Barcelona Clinic Liver Cancer [BCLC] stage B, 68% BCLC stage C, 36% with microvascular invasion; 56% received A/B and 40% received D/T treatment. PSMA was positive in 96% of pts at baseline with median SUVmax 14.3 (range 5.1-40.5) and median background liver SUVmax 3.9 (range 2.1-6.8). Median (95%CI) PFS was 5.6 m (4.6-12.5) by both RECIST and mRECIST. Median (95%CI) OS was 18.6 m (7.2-not estimable), with 56% deceased. The observed agreement between PET/CT adapted PERCIST criteria compared to RECIST and mRECIST in determining the best response was 46% and 50% and weighted kappa of 0.63 (95% CI: 0.37-0.90) and 0.66 (0.41-0.92), respectively. Observed agreement between PERCIST compared to RECIST and mRECIST for responders’ assessment was 67% and 71% with Cohen’s kappa of 0.36 (0.03-0.68) and 0.43 (0.11-0.76), respectively. Conclusion: In this cohort, PSMA PET/CT avidity was observed in all but one pt with advanced HCC, each demonstrating moderate to high SUVmax values. Median OS and PFS were consistent with outcomes reported in clinical trials. Response assessment using 68Ga-PSMA PET/CT according to PERCIST criteria showed good concordance with both RECIST and mRECIST standards. Analysis of immune biomarkers is ongoing. Citation Format: Nguyen H. Tran, Jacob Hirdler, Ajith Antony, Jacob Teske, Sudhakar K. Venkatesh, Amit Mahipal, Michael S. Torbenson, Scott M. Thompson, Thor R. Halfdanarson, Zhaohui Jin, Lionel Aurelien Kankeu Fonkoua, Leslie A. Washburn, Alexander Revzin, Haidong Dong, Robert R. Mcwilliams, Aminah Jatoi, Hani M. Babiker, Mitesh J. Borad, Tanios Bekaii-Saab, Gregory J. Gores, Lewis R. Roberts, Geoffrey B. Johnson, Ajit H. Goenka. Prospective evaluation of 68Ga-PSMA PET imaging in advanced hepatocellular carcinoma patients undergoing first line immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 2611.

Abstract Background: Tarlatamab, a Delta-like ligand (DLL3)/CD3-targeted bispecific T-cell engager (TCE) is FDA approved in patients (pts) with extensive stage small cell lung cancer (ES-SCLC), after progression on frontline chemoimmunotherapy. We aimed to evaluate the immune cell profile in pts who received this therapy in standard-of-care (SOC) practice with progression free survival (PFS) less than and greater than two months (mo). Methods: Patients who received tarlatamab at Mayo Clinic Rochester and consented to immuno phenotyping of blood are included in the present study. Immune phenotyping was performed on whole blood by flow cytometry and analyzed by Kaluza. Data analysis was performed with Microsoft Excel and PRISM. Results: Eighteen patients with median age 64 (range 37-79) were included in the study. 66% of our cohort were women and 83% had present or past history of smoking, with an average of 40 pack years (range 26-60). With a median follow-up of 2 months, the median PFS for the cohort was 1.5 mo (range 0.33-2.76 months). 61% (13/18) of patients had PFS <2mo. 39% (5/18) had PFS>2mo and of which, three patients had partial response with one maintaining stable disease and one patient with mixed response. At baseline (BL), there were no difference in T cell, CD4 or CD8 cell count between patients in the PFS<2mo and PFS>2mo groups. Patients with PFS<2mo had higher exhausted CD8 T cells compared to those in the PFS>2mo group (CD8+PD1+TIGIT+CD57+, PFS<3mo vs >3mo, cells/mL: 7.14±4.28, 1.58±1.37, p=0.009). Additionally, when analyzing the B-cell population, the PFS<2mo group had lower percentage of B cells compared to the group with PFS>2mo at baseline (6.0±7.5, 10.4±14, p=0.02). At day 7, the group with PFS<2mo had lower Treg compared to the group with PFS>2mo (2.88±1.38, 4.60±1.47, p=0.02). Also, the PFS<2mo group had an increase of B cells compared to the group with PFS>2mo at day 7(<2mo vs >2mo: 10.0±14, 4.37±3.07, p=0.04). Finally, the group with PFS>2mo had decrease in total monocytes (mono), classical mono, and immunosuppressive cells (PFS<2mo vs >2mo, Mono: 340±347, 253±106, p=0.04. Classical mono: 305±283, 155±109, p=0.02. CD14+HLA-DRneg: 105.8±96, 12±39, p=0.03) compared to the group with PFS<2mo by day 7. While no changes were seen between BL and day 7 for intermediate mono in PFS<2mo group, PFS>2mo group had decreased post treatment intermediate monocytes (BL vs day 7, cells/mL, intermed mono: 32.5±15,17.7±6.2, p=0.03). Conclusion: In this study investigating the SOC outcomes of tarlatamab, early progression was associated with higher presence of exhausted CD8 T cells, B cells, and immunosuppressive monocytes. Analysis of additional patients will be shared at AACR meeting. Citation Format: Dhauna Karam Prasad, Andre De Menezes Silva Corraes, Malvika Gupta, Audrey Ma, Chen Wu, Zuoyi Shao, Kevin Reagan, Rayaan Kamal, Ashley Potter, Abdullah Al-Ajmi, Syeda Mina, Sykler J. Taylor, Antonious Hazim, Anastasios Dimou, Kaushal Parikh, Mohammed Shanshal, Ailsa Luce, Anna Schwecke, Julian Molina, Aaron Mansfield, Katherine Smith, Lucy Holmes, Haidong Dong, Yi Lin, Konstantinos Leventakos. Immune cell profile changes in patients treated with tarlatamab for extensive stage small cell lung cancer in real world practice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3931.

Abstract Background: Melanoma brain metastases (MBM) represent a biologically distinct and clinically aggressive subset of melanoma. Comprehensive molecular characterization focused on intracranial disease remains limited. We aimed to define the genomic landscape of MBM and compare these findings with public melanoma datasets. Methods: We retrospectively identified 166 patients with histologically confirmed MBM across Mayo Clinic tri-sites (2011-2025). Molecular testing was performed in 123 patients (74.1%). Comprehensive next-generation sequencing (NGS; ≥300-gene platforms including Tempus, FoundationOne, Caris, NeoGenomics, and MayoComplete Solid Tumor Panel) was available in 41 patients (24.7%). Intermediate-depth profiling using the MayoComplete Melanoma Panel (17 genes) was performed in 21 patients (12.7%), and a targeted 5-gene melanoma driver panel (BRAF, NRAS, KIT, GNAQ, GNA11) in 52 patients (31.3%). cfDNA-based NGS was available in 12 patients (7.2%). Genomic alterations were summarized and benchmarked against TCGA-SKCM and MSK-IMPACT datasets via cBioPortal. We considered assay heterogeneity, as Mayo panels varied in sequencing depth and CNV coverage, and hybrid-capture platforms often under-detect TERT promoter hotspots. Results: Patients had a median age of 67 years, and 63% were male. BRAF mutations occurred in 48.8% (BRAF V600E/K 41.6%; non-V600 7.2%). Additional MAPK alterations included NRAS (17.5%), KIT (5.4%), GNAQ (1.2%), and GNA11 (0.6%). In the comprehensive NGS subset, tumor-suppressor alterations included CDKN2A (17.5%), PTEN (7.8%), NF1 (9.0%), TP53 (8.4%), and TERT promoter mutations (22.9%). Median TMB was 11.55 mut/Mb (IQR 5.0-25.5). Co-alterations included BRAF+CDKN2A (7.2%), BRAF+PTEN (4.2%), NRAS+CDKN2A (4.2%), NRAS+PTEN (1.2%), and CDKN2A+PTEN (3.6%); overall, 18.1% harbored MAPK driver + tumor-suppressor co-alterations. Compared with TCGA and MSK cohorts, MBM showed similar MAPK driver frequencies but fewer MAPK + tumor-suppressor co-alterations and lower CDKN2A, PTEN, and TP53 disruption, alongside a more prevalent of TERT promoter mutations (22.9% vs 7% and 2.1%), which may partly reflect coverage differences. Conclusion: MBM exhibit a distinct genomic profile characterized by reduced tumor-suppressor loss, fewer MAPK-tumor-suppressor co-alterations, and higher prevalence of TERT promoter mutations. While assay heterogeneity limits direct cross-cohort comparisons, these patterns suggest potentially distinct biological features of intracranial melanoma and underscore the need for harmonized, MBM-specific molecular studies to guide therapeutic development. Citation Format: Dina Elantably, Joseph B. Parker, Jakob Hamilton, Ahmed Abdelhakeem, Oluwatayo Adeoye, Saivaishnavi Kamatham, Winston Tan, Arkadiusz Z. Dudek, Anastasios Dimou, Matthew S. Block, Robert McWilliams, Svetomir Markovic, Mahesh Seetharam, Roxana Dronca, Ruqin Chen. Genomic landscape of melanoma brain metastases: Real-world analysis and comparison with public melanoma cohorts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 2107.

Abstract Introduction/Objectives: The CARMA1-BCL10-MALT1 (CBM) signalosome plays crucial role in mediating antigen receptor-induced activation of NF-κB transcription factor and subsequent lymphocyte activation. The effector protein of the signalosome, MALT1, functions both as a scaffold to recruit downstream NF-κB signaling machinery, and as a protease to cleave and inactivate multiple substrates including negative regulators of NF-κB. Constitutive MALT1 activation, which can occur as a result of gain-of-function mutations of the B cell receptor, CARMA1, BCL10 or chromosomal translocation involving the MALT1 gene, underlies the pathogenesis of multiple lymphoid malignancies including activated B-cell type-diffuse large B-cell lymphoma (ABC-DLBCL) and MALT lymphoma. We previously identified G-protein-coupled receptor kinase 2 (GRK2) as a tumor suppressor in MALT1-dependent lymphomas which binds MALT1 and inhibits MALT1 scaffolding and proteolytic activities. Accordingly, GRK2 mRNA levels are markedly lower in a subset of DLBCL tumors compared to normal B cells and lower GRK2 level in ABC-DLBCL is associated with reduced patient survival. In current study, we sought to investigate the mechanism of how GRK2 levels are regulated in ABC-DLBCL. Methods/Results: Using DICER1 depleted cells, we showed that globally impaired miRNA processing leads to increased GRK2 protein levels. We then conducted bioinformatic analyses of patient tumor samples and performed screening via microRNA Data Integration Portal to identify microRNAs that target GRK2 in ABC-DLBCL. Further GRK2 3’UTR reporter assay confirmed direct targeting of GRK2 by candidate miRNAs. ABC-DLBCL cell lines, OCI-LY3 and TMD8, which demonstrate reduced GRK2 mRNA expression compared to primary B cells, show elevated expression of candidate GRK2-targeting microRNAs. Stable overexpression of miR-125a, 125b, or 148b in OCI-LY3 or TMD8 cells led to reduced GRK2 expression, enhanced MALT1 activity and increased cell proliferation. Conversely, in vitro inhibition of candidate miRNAs using anti-miRNA Locked Nucleic Acids (LNA) inhibitors led to enhanced GRK2 expression, reduced MALT1 activity and decreased cell proliferation. Importantly, treatment of mice with inhibitors of miR-125b and miR-148b abrogates the growth of ABC-DLBCL xenograft tumors in vivo. Conclusion: We have identified miRNAs that negatively regulate GRK2 expression in ABC-DLBCL. These GRK2-targeting miRNAs serve a pro-tumorigenic role by promoting MALT1 oncoprotein’s scaffold and protease activity. Furthermore, inhibitors of these miRNAs can enhance GRK2 expression and thereby suppress MALT1 activity and MALT1-dependent tumor cell proliferation, both in vitro and in vivo. These studies suggest that microRNA inhibitors which enhance GRK2 expression could represent a novel approach for restraining MALT1-dependent lymphomagenesis. Citation Format: Jing Cheng, Mei Smyers, Matt Trotta, Neil M. Carleton, Lisa M. Maurer, Uma R. Chandran, Min Xia, Ari M. Melnick, Peter C. Lucas, Linda M. McAllister-Lucas. MicroRNAs targeting tumor suppressor GRK2: Novel potential therapeutic strategies for restraining MALT1-dependent DLBCL [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 2061.

Abstract Lipid metabolism plays an important role in lung cancer growth, survival, and therapeutic resistance. Stearoyl-CoA desaturase 1 (SCD1), the enzyme that converts saturated fatty acids (SFAs) into monounsaturated fatty acids (MUFAs), represents a metabolic vulnerability since cancer cells depend on MUFAs for membrane biosynthesis, ER homeostasis, and alternative energy to glucose. SSI-4 (a.k.a MTI-301) is a selective SCD1 inhibitor currently in Phase I clinical evaluation for metastatic, unresectable, or refractory solid cancers, but its activity in non-small cell lung cancer (NSCLC) has not yet been characterized. To evaluate how NSCLC models respond to SCD1 blockade, we performed an initial screen of a panel of 17 human non-small cell lung cancer cell lines treated with 100 nM SSI-4 under defined serum conditions. Cell viability assays identified 9 responding cell lines, and dose-response studies confirmed IC50 values ranging from approximately 0.65 to 45.5 nM. Rescue experiments showed that adding oleic acid, an SCD1 regulated MUFA, reversed SSI-4-mediated growth inhibition, confirming mechanistically that this effect occurs through SCD1 blockade. Western blot analysis confirmed that SSI-4 treatment increased markers of endoplasmic reticulum (ER) stress and apoptosis in sensitive lines, consistent with disruption of lipid homeostasis. In contrast, non-responsive lines exhibited minimal induction of these stress pathways and retained viability despite treatment. Soft agar assays further showed that SSI-4 reduced anchorage-independent colony formation in responsive lines, indicating that SCD1 inhibition suppresses a key malignant growth property in these NSCLC models. Collectively, these findings demonstrate that SSI-4 selectively inhibits proliferation in a subset of NSCLC cells through an SCD1-dependent mechanism by reducing MUFA availability and activating stress and apoptotic signaling. This work establishes a framework for subsequent in vivo studies and lays the foundation for exploring SCD1 inhibition as a potential therapeutic strategy for patients with limited treatment options in NSCLC, while also advancing understanding of the mechanisms by which SCD1 supports tumor survival. Citation Format: Valeria Romina Salerno Gonzales, Lauren Antal, Tamiel Nichole Turley, John A. Copland III. Inhibition of stearoyl-CoA desaturase 1 (SCD1) by SSI-4 as a therapeutic strategy in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 2942.

Abstract Background: Cancer survivorship requires significant contributions from family caregivers at home. This role can be burdensome because family members play a vital role in the physical, functional, and emotional well-being of patients diagnosed with cancer. Although optimum care throughout the care continuum requires significant caregiver support at home, family caregivers' contribution to survivorship care is usually neglected. We provide the preliminary outcomes of caregivers' challenges and experiences in providing care and survivorship support to Black cancer survivors. We also identified ways to provide support for family caregivers. Methods: This qualitative study obtained information from 8 caregivers who care for Black cancer survivors who have completed treatment in the United States. The study used a phenomenological design to obtain data from participants. In-depth interviews focused on participants' lived experiences caring for Black patients with cancer. The study captured caregivers' personal stories of how they dealt with diagnosis, feelings, emotions, reactions, understanding of the disease, prognosis, and treatment options and decision process, as well as survivorship of their care recipients. All interviews were video recorded and transcribed verbatim. The transcript of each participant's interview was reviewed, analyzed, and coded, with emerging themes interpreted. Results: The major cahllenges identified were (1) lack of knowledge of cancer, the disease and treatment course before the diagnoses; (2) home care burden, which include the challenges of combining care for a sick person at home with caring for other members of the family and taking care of domestic chores; (3) patient care navigation, including identifying healthcare professional for specialist care, adequate health insurances, scheduling doctors' appointment, transportation, insurance and treatment paperwork; (4) financial challenges, especially keeping up with job, family income reduction, increase out of pocket spendings, as well as expensive drugs and treatment co-pays. Most of the caregivers agreed that they neglected their personal health while caring for their care recipient. All caregivers wished they received more information and training on how to care for a patient with cancer. Possible solutions identified were care packets providing information on cancer and how to provide care at home, patient care navigation to social determinants of health and financial support programs, counselling for mental health and emotional support, peer support groups for caregivers, health checks, and a contact to call for support. Conclusion: Caring for cancer patients at home is very challenging; having a care packet and caregiving training is important to support survivorship and reduce the caregiving burden experienced by family caregivers. Citation Format: Opeyemi Oreoluwa Bolajoko, Jada Melton, Mary Ellen Young, Folakemi T. Odedina. Perspectives on cancer survivorship: Voices of family caregivers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 1248.

Abstract Ovarian endometrioid carcinoma (OEC) is the second most common histotype associated with the most favorable prognosis among ovarian carcinomas. Similar to endometrial carcinoma, OEC exhibit significant molecular diversity. We aimed to develop a practical immunohistochemical (IHC) prognosticator by integrating IHC biomarkers with clinical substage, and surgical outcomes. This multi-institutional study included participants with primary invasive OEC from the Alberta Cancer Registry (AOVT), Mayo Clinic, and Disease of the Ovary and their Evaluation Study (DOVE). Pathology review excluded misclassified high-grade serous and mesonephric carcinomas leaving 422 OEC cases (AOVT N=158; DOVE N=143; Mayo N=121) with available tumor biospecimens who did not receive neoadjuvant treatment. Clinical characteristics included age, stage, grade, residual disease and 5-year survival. Clinical risk group was defined by combining stage and residual disease: Low (FIGO stage IA/IB & no macroscopic disease), Intermediate (stage IC-II& no macroscopic disease), High (stage III/IV or macroscopic disease). Tissue microarrays were stained for TP53, PMS2, MSH6, PGR, and CTNNB1 using IHC and were scored by a single pathologist. Tumors were hierarchically categorized as TP53-abnormal (TP53abn)/PGR-loss, mismatch-repair deficient (MMRd, via PMS2 and MSH6), nuclear-CTNNB1 (nCTNNB1), or no-specific-immunohistochemical-profile (NSIP). Overall survival (OS) at 5 years was compared across clinical risk and biomarker groups using Cox regression, adjusted for age and site to generate hazard ratios (HR), and 5-year survival rates (5-YSR). High clinical risk group was associated with worse 5-year OS compared to low & intermediate risk (p<0.0001). Hierarchical IHC biomarker groups were also associated with 5-year OS, adjusted for age and study site (p<0.0001), with consistently worse survival for combined TP53abn/PGR-loss (n=17, HR=6.07, 95% CI 2.78-13.26), PGR-loss only (n=55, HR=4.17, 95% CI 2.19-7.94), TP53abn only (n=29, HR=2.04, 95% CI 0.85-4.90), and better survival for nuclear-CTNNB1 (n=146, HR=0.22, 95% CI 0.07-0.65) compared to NSIP (n=132). Within the low-risk group, MMRd, nCTNNB1, or NSIP had greater than 97% 5-YSR, while OEC with TP53abn/PGR-loss or PR-loss only had less than 75% 5-YSR. Within the intermediate group, only nCTNNB1 exceeded a 5-YSR of greater than 97%. Within the high-risk group, 5YSR for nCTNNB1 OEC was 90.9%, compared to only 16.7% for TP53abn/PGR-loss. This IHC-based algorithm refines prognosis beyond clinical substage. It identifies low-risk patients with unfavorable prognosis (TP53abn/PGRloss, PGR loss only) who may benefit from adjuvant therapy, and also patients with favorable prognosis within the intermediate group for whom adjuvant therapy could be de-escalated. Further patient selection for chemo vs. hormone therapy in the high-risk group may be improved by biomarkers. Citation Format: Gamaliel Taengwa, Hunter J. Atkinson, Bryan M. McCauley, Sebastian M. Armasu, Chen Wang, Jennifer A. Doherty, Holly R. Harris, Ellen L. Goode, Martin Koebel, Stacey J. Winham. IHC-based prognostic sub-stratification of ovarian endometrioid carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 1184.

Abstract Background: Personalizing chemoradiotherapy (chemoRT) for locally advanced non-small cell lung cancer (LA-NSCLC) is limited by the lack of early biomarkers that inform response during treatment. Current circulating tumor DNA (ctDNA) molecular residual disease assays predict post-treatment outcomes but lack mid-treatment utility. ctDNA burden estimation has traditionally relied on variant-centric metrics such as maximum variant allele fraction (Max VAF), which rely on mutation-specific signals and may be confounded by histology-dependent shedding variability, allelic imbalance, and clonal hematopoiesis. Here we present circulating tumor fraction estimate (ctFE), a machine-learning composite score that integrates VAF distributions, copy-number alterations, and germline B-allele frequency deviations to approximate global tumor burden using a widely available, tumor-naïve clinical platform. Methods: A burden-based ctFE threshold was derived using pre-treatment plasma from a prospective phase II clinical trial of MR-guided hypofractionated chemoRT (LA-WU, n=26), locked, and applied unchanged to early mid-treatment samples (day 10-14). To test scalability and generalizability, its prognostic performance was validated in two real-world cohorts: 94 LA-NSCLC patients receiving definitive chemoRT (LA-RW) and 309 oligometastatic NSCLC patients receiving consolidative RT (OM-RW). ctFE and Max VAF were compared as continuous predictors across cohorts. Results: ctFE consistently outperformed Max VAF. In LA-WU, pre-treatment ctFE was associated with overall survival (OS HR=1.15, p=0.04) and progression-free survival (PFS HR=1.84, p=0.009), whereas Max VAF was not. Mid-treatment ctFE remained prognostic for PFS (HR=1.14, p=0.026). Early ctFE dynamics defined three molecular response groups with marked OS separation: consistently low, responder, and nonresponder groups (median OS 60.8 vs 13.0 vs 2.9 months, respectively; p<0.001). In multivariable models including both biomarkers, higher ctFE remained independently associated with worse survival in LA-RW (OS HR=1.88, p=0.010) and OM-RW (OS HR=1.37, p=0.040; PFS HR=1.45, p=0.008), whereas Max VAF did not. The locked ctFE threshold stratified OS across all cohorts (LA-WU HR=5.93; LA-RW HR=9.08; OM-RW HR=2.26; all p<0.001). Conclusion: ctFE provides clinically meaningful pre- and mid-treatment risk stratification and consistently outperforms Max VAF across locally advanced and oligometastatic NSCLC cohorts. We show that ctFE is a biologically informative, clinically generalizable and scalable ctDNA burden metric measurable using a tumor-naïve, off-the-shelf assay, supporting its practical utility in biomarker-adapted radiotherapy strategies. Citation Format: Ayesha Hashmi, Jessica Linford, Pradeep S. Chauhan, Kaushal Parikh, Rotem Ben-Shachar, John Guittar, Malvika Pillai, Jyoti Patel, Matteo Bergsagel, Nicholas P. Semenkovich, Kenneth R. Olivier, Sean S. Park, Dawn Owen, David M. Routman, Katie N. Lee, Alex D. Sherry, Aaron S. Mansfield, Daniel Morgensztern, Ramaswamy Govindan, Clifford G. Robinson, Carmen Bergom, Saiama N. Waqar, Bruna Pellini Ferreira, Gregory R. Vlacich, Aadel A. Chaudhuri. Early ctDNA quantification by ctFE outperforms Max VAF for survival stratification across locally advanced and oligometastatic NSCLC treated with radiotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 1183.