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Abstract Background Extramammary Paget disease (EMPD) is a rare cutaneous adenocarcinoma. While localized disease has an excellent prognosis, metastatic EMPD is aggressive with no standardized systemic therapy. This study characterizes the clinicopathologic and molecular landscape of metastatic/recurrent EMPD to identify therapeutic vulnerabilities. Patients and methods We conducted a retrospective cohort study of 26 patients with metastatic or distantly recurrent EMPD treated at Mayo Clinic (2000-2025). Descriptive statistics were used to summarize baseline characteristics. Survival outcomes were estimated using Kaplan–Meier methods, with group comparisons performed using log-rank testing. Continuous variables were compared using nonparametric tests, and categorical variables were analyzed using appropriate comparative tests. Pathway-level genomic correlations with TCGA reference cohorts were assessed using Spearman rank correlation. Treatment responses were retrospectively evaluated from radiologic reports. Results The cohort was predominantly male (73.1%) and White (92.3%), with a median age of 68 (IQR, 53-79). Lymph nodes were the most common metastatic site (61.5%). The median overall survival (OS) was 20.0 months (95% CI, 0-40.4). IHC showed universal CK7 and GATA3 positivity, with 80% androgen receptor (AR) expression. HER2 was positive (3+) or amplified in approximately one-third of cases. NGS revealed frequent mutations in TP53 (68.8%), ERBB2 (50%), and CDKN2A/B (50%). A “triple-hit” deletion at the 9p21 locus (CDKN2A/B/MTAP) was identified in 25% of cases. Genomic profiling showed strong similarity to HER2+ breast and urothelial carcinomas. HER2-directed therapy was associated with longer overall survival (median OS 73.0 months [95% CI, 0-177.9] vs 19.0 months [95% CI, 0-41.4]; HR 0.50 [95% CI, 0.0-177.9], P = .3), although this difference did not reach statistical significance. Conclusion Metastatic EMPD exhibits distinct clinicopathologic and molecular features, including high AR and HER2 expression, TP53 and CDKN2A/B alterations, and similarity to systemic HER2+ malignancies. The observed activity of HER2-directed therapies in this cohort suggests the potential value of further investigating biomarker-guided treatment strategies in metastatic EMPD. NGS-guided profiling may inform precision treatment strategies, including AR-targeted therapy and emerging MTAP-directed approaches.

TPS6126 Background: Oral cavity cancers (OCC) are a rare subtype of head and neck cancer (HNC) with poor outcomes and limited second-line treatment options in the recurrent or metastatic (R/M) setting. Treatment-related morbidity and repeated local recurrences in OCC result in significant impairment of function and quality of life. Rural OCC patients comprise a sizable portion (50%) of our practice and are usually of lower socioeconomic status with lack of access to specialist care. They also have multiple barriers to treatment access and ancillary services, translating to poorer clinical outcomes. There is a critical need for effective and accessible therapies for R/M OCC in rural patients. Triple oral metronomic chemotherapy (TOMC) with Methotrexate, Erlotinib and Celecoxib (MEC) suppresses angiogenesis and activates antitumor microenvironment in HNC. Studies using TOMC in R/M OCC outside the US show reasonable efficacy (6-month OS 52.9%), better safety and lower cost compared to standard second line options. We hypothesize that a decentralized clinical trial with TOMC in R/M OCC is feasible, safe and effective in addition to being economical and accessible for rural patients. Methods: MC240701 is a single institution, open label, decentralized, single arm pilot study of MEC in patients with R/M OCC. Eligible pts must be ≥18 years old, have pathologically confirmed R/M OCC not amenable to curative-intent therapy, ECOG 0-2 and adequate organ function. At least 1 measurable lesion by RECIST 1.1 OR non-measurable disease (evident mucosal lesions, CNS/bone disease, lesions not meeting RECIST criteria) is permitted. Patients must have received standard first line immunotherapy with or without chemotherapy OR should be unable/unwilling to receive first line treatment. Key exclusion criteria include patients unable to take pills by mouth, serious medical co-morbidity or autoimmune disease, immunocompromised patients and other active malignancy. Primary endpoint is to demonstrate feasibility of decentralized clinical trials, secondary outcomes include overall response rate, progression free and overall survival and toxicity. Additional goals are to evaluate patient impact of decentralized treatment through surveys and interviews After initial screening and evaluation, patients are remotely consented and will receive study drugs by mail. All patients will receive the same treatment of Methotrexate 9mg/m 2 PO weekly, Erlotinib 150 mg PO daily, and Celecoxib 200 mg PO BID, each cycle will be 28 days. Treatment will continue until disease progression or treatment tolerance, study duration is for 2 years. All subsequent clinical and laboratory monitoring and response assessments (every 3 cycles) will be remotely performed or have an option for local testing. Enrollment began July 2025 and 4 out of planned 25 patients have been accrued. FDA IND:174540. Clinical trial information: NCT06997068 .

e18026 Background: Immune checkpoint inhibitor (ICI) therapy is part of standard of care first-line therapy for recurrent or metastatic (R/M) HNSCC. However, less than 20% of patients (CPS ≥1) have an objective response to ICI monotherapy, and most tumors progress within ~3 months. We sought to improve the proportion of patients who benefit from a chemotherapy-free regimen by combining intratumoral (IT) VV1 oncolytic virus (VSV-IFNβ-NIS) injections with the anti-PD-1 antibody, cemiplimab. We report a pre-planned analysis of Simon's stage 1 results. Methods: We activated a phase 2 study testing the efficacy of first line IT VV1 plus cemiplimab in 1 st line patients with R/M HNSCC. A Simon's two-stage design was employed whereby 10 patients would be accrued in stage 1, and if 3 or more responses were observed, 12 additional patients would be accrued for stage 2. The primary endpoint was objective response rate (ORR) per investigator (RECIST 1.1). Eligible patients had untreated R/M HNSCC from primary oropharynx, oral cavity, hypopharynx, or larynx sites with CPS ≥1. Patients had to have at least one measurable lesion amenable to IT injection. Treatment comprised of IT injections to 1-5 lesions of oncolytic VV-1 virus and IV cemiplimab 350 mg on day 1, repeated every 21 days. Each lesion could be injected 3 times; a 4th injection was allowed if a partial response (PR) was achieved after 3 injections. Cemiplimab could be continued for up to 2 years until progression or unacceptable toxicity. Results: Patient and tumor characteristics, as well as efficacy and toxicity are summarized in the table below. Ten patients were treated at the time of Stage 1 analysis, with 3 showing a confirmed PR for ORR of 30%. Responder CPS scores were 45, 12 and 20%. Two of the responders subsequently showed progression after 6.2 and 9.9 months, the third has maintained PR at 7.7 months to date. Eight of 10 patients showed decrease in the sum of target lesion size (mean decrease of 16%; range -57 to 77%). One grade 2 event of ICI nephritis resolved with corticosteroid treatment. Conclusions: Three patients showed confirmed PR by RECIST 1.1 in Simon's stage 1, meeting criteria to proceed to Simon's stage 2. A total of 22 patients in the HNSCC will be enrolled. VV1 plus cemiplimab shows promise in first line R/M HNSCC based on these initial results. Clinical trial information: NCT04291105 . Patient demographics. N (treated) 10 Sex 20% female Median age (y) 60 (54 – 76) Oropharynx 7 HPV+ 7 Oral cavity 3 PD-L1 CPS median (range) 7.5 (1-45%) Locoregional injection 3 Distant injection 6 Local and distant injection 1 Best response (RECIST 1.1) PR 3 SD 5 PD 2 Adverse Events #pts any VV1/cemiplimab-related G3 AE 4 Lymphopenia 3 Elevated ALK 1

6123 Background: Pemetrexed (PTX) is safe and tolerable with responses reported in pts with R/M SGC. Given enhanced responses with PTX and pembrolizumab (PMB) for lung cancer, we hypothesized that PTX and PMB will have activity for SGC. Herein we present the efficacy results in pts with adenoid cystic carcinoma (ACC). Methods: MC200708 is a single arm phase II study of PTX and PMB in pts with R/M SGC (NCT04895735) with 2 cohorts: ACC (cohort A) and non-ACC (cohort B). Key eligibility criteria: ≥18 years, ECOG 0-1, measurable disease. Prior ICI and/or PTX was allowed. Key exclusion criteria: serious comorbidities, autoimmune disease and brain metastases. Simon’s 2-stage design was used for each cohort. Primary endpoint was overall response rate (ORR) for Cohort A but was amended to clinical benefit rate (CBR=SD+PR+CR) due to prolonged SD in several pts. Secondary endpoints: progression free survival (PFS), overall survival (OS), and toxicity. Exploratory analyses in Cohort A1 (post-amendment pts) included PSMA PET imaging and circulating PSMA extravesicles (EVs) as a biomarker. All pts received PTX 500 mg/m2 IV + PMB 200 mg IV q3 weeks until progression or treatment intolerance. Imaging was q3 cycles. Results: 20 pts (11 Cohort A + 9 Cohort A1) were enrolled from August 2021-Feb 2025. All 20 patients were eligible and received ≥ 1 cycle of treatment. Median age was 60.5 yrs, 50% male, performance status 0 (80%) or 1 (20%). 11 pts had no prior therapies (55.0%). The remaining pts had 1 (35%) or 2 (10%) prior lines of therapy. 75% of pts had no prior ICI. In Cohort A, the ORR was 0% (0 of 11). Cohort A1 met criteria for success based on CBR with 1 PR (12.5%) and 5 SD (62.5%) in the first 8 pts. For the whole cohort of 20 patients, the ORR was 5% (95% CI: 0.1-24.9) and the CBR rate was 75% (95% CI: 51-91) with 1 PR and 14 pts with SD. The duration of response for the 1 PR patient was 12.4 months. The median duration of response for the 15 pts with SD was 7.5 (2.0-29.7) months. 3 pts (15%) had PD and 2 pts (10%) went off prior to response assessment. Median cycles of treatment was 4 (2-30). In the 17 pts who discontinued, treatment was stopped in 9 (53%) for PD, 4 (23.5%) due to adverse events (AE), and 4 (23.5%) due to physician/patient preference. With a median follow-up of 14.5 months (1.5-39.2), the 1-year PFS rate is 52.1% (32.6 – 83.2%) and the OS rate is 82.1% (95% CI: 65.6 – 100%). The overall grade 3+ AE rate regardless of attribution was 80% (16/20). The most common grade 3 AEs were lymphocyte count decrease (40%), hypertension (20%), fatigue (10%), and pneumonitis (10%). 2 pts had a grade 4 AE (lymphocyte count decrease and thrombotic thrombocytopenic purpura). There were no treatment-related deaths. Analysis of correlative studies for Cohort A1 with PSMA imaging and EV biomarker ongoing. Conclusions: PTX and PMB has modest activity in pts with R/M ACC with CBR of 75% and prolonged benefit for some patients. Clinical trial information: NCT04895735 .

IMPORTANCE Neoadjuvant chemoimmunotherapy has high rates of pathologic response and improved prognosis among solid tumors. Its role in head and neck squamous cell carcinoma (HNSCC) remains understudied. OBJECTIVE To summarize the efficacy associated with neoadjuvant chemoimmunotherapy regimens in HNSCC and to compare the efficacy associated with neoadjuvant chemoimmunotherapy vs immunotherapy alone in locoregionally advanced resectable HNSCC prior to definitive surgery. DATA SOURCES A librarian-led systematic review was conducted using multiple electronic databases, including Medline, EMBASE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Scopus, following Preferred Reporting Items for Systematic Reviews and Meta- Analyses (PRISMA) guidelines. Databases were queried from inception to October 2024. STUDY SELECTION Inclusion criteria included prospective interventional trials that have completed accrual, with results published in English. Only trials of resectable, treatment-naive HNSCC were included. Exclusion criteria included lack of reporting on pathologic response or Response Evaluation Criteria In Solid Tumors (RECIST) version 1.1 response. DATA EXTRACTION AND SYNTHESIS Two investigators independently conducted title, abstract, and full-text reviews per PRISMA guidelines. Primary outcomes extracted were major pathologic response (MPR) and complete pathologic response (CPR) at surgery and complete response (CR) on imaging by RECIST 1.1. Secondary outcomes included 1-year overall survival (OS) and toxic effects. MAIN OUTCOMES AND MEASURES A meta-analysis was performed using a binary random-effects model to determine the pooled proportion of primary outcomes in the immunotherapy and chemoimmunotherapy groups. Heterogeneity was reported as I 2 . RESULTS A total of 751 patients (502 [77%] male; age range, 27-87 years) across 23 studies were included in the meta-analysis, including 357 patients (47%) who underwent chemoimmunotherapy, 102 patients (14%) who underwent dual-agent immunotherapy, and 292 patients (39%) who underwent single-agent immunotherapy. Pooled rates of MPR plus CPR were 66% (95% CI, 58%-73%; I 2 = 0.59) for chemoimmunotherapy, 18% (95% CI, 6%-29%; I 2 = 0.65) for dual-agent immunotherapy, and 6% (95% CI, 3%-9%; I 2 < 0.01) for single-agent immunotherapy. Across all groups, 1-year OS rates ranged from 88% to 96% for single-agent immunotherapy, 88% to 96% for dual-agent immunotherapy, and 88% to 100% for chemoimmunotherapy. Grade 3 to 5 adverse events were reported in 61 of 210 patients (29%), 2 of 67 patients (3.0%), and 36 of 210 patients (17%) among the reporting studies in the single-agent immunotherapy, dual-agent immunotherapy, and chemoimmunotherapy groups, respectively. CONCLUSIONS AND RELEVANCE These findings suggest that neoadjuvant chemoimmunotherapy regimens were associated with higher pathologic and radiographic response rates compared with immunotherapy alone in locoregionally advanced HNSCC. These results call for phase 3 trials comparing these neoadjuvant regimens head to head.

Caudal type homeobox 2 (CDX2) is an intestine-specific transcription factor that serves as a diagnostic marker of enteric differentiation and may also reflect tumor behavior and therapeutic susceptibility. Emerging evidence suggests that CDX2 expression may predict sensitivity to fluoropyrimidine-based therapy independent of tissue of origin. We report a retrospective case series of three patients with metastatic adenocarcinoma (aggressive variant prostate, minor salivary gland, and intestinal-type sinonasal tract) exhibiting strong CDX2 nuclear expression. In all cases, tumors were refractory to or lacked established standard systemic therapy. Treatment decisions were informed by the CDX2-positive enteric phenotype, leading to the initiation of fluoropyrimidine-based regimens. Response was assessed using PET-CT and MRI. All three patients achieved marked metabolic and clinical responses, including a sustained complete metabolic response in the prostate cancer case and durable disease control in the salivary gland and sinonasal tumors. These findings highlight CDX2 as a potential biomarker requiring validation, which may identify tumors intrinsically susceptible to fluoropyrimidines regardless of anatomical origin. CDX2 immunohistochemistry is widely available and inexpensive, and may complement genomic profiling in rare malignancies or in settings where standard treatment algorithms are limited. This report is hypothesis-generating and not intended to estimate response rates or treatment efficacy.

TPS2677 Background: Despite the success in hematologic malignancies, CAR T therapies face significant challenges in solid tumors due to the lack of tumor-specific targets that distinguish cancer from normal cells. EGFR plays a critical role in oncogenesis across several cancers and is often upregulated (TCGA 2022). While monoclonal antibodies targeting EGFR have demonstrated efficacy, these approaches are often limited by on-target, off-tumor toxicities, such as skin rash, which constrains dose escalation and efficacy (Macdonald, et al. J Am Acad Dermatol . 2015). A2B395 is an allogeneic, logic-gated, EGFR-targeted Tmod CAR T therapy designed to address these limitations and provide a convenient and consistent off-the-shelf option. This therapy incorporates 2 CARs: an activator targeting EGFR, and a blocker targeting HLA-A*02. The activator recognizes EGFR on both tumor and normal cells, while the blocker inhibits CAR T activity against normal cells with preserved HLA expression and decreases the risk for graft-versus-host disease (Hamburger, et al. Mol Immunol . 2020). To address potential host-vs-graft response, an shRNA expression module targeting B2M is included in the Tmod construct, which significantly reduces major histocompatibility complex class I levels and subsequent host immune response (DiAndreth, et al. Clin Immunol. 2022). Importantly, the Tmod system is modular and adaptable to multiple targets. Initial data on autologous Tmod CAR T therapy suggest reduced off-tumor toxicity and encouraging clinical efficacy (Grierson, et al. SITC 2024. Abstract 588). A2B395 represents a novel approach for EGFR-expressing solid tumors with HLA-A*02 LOH. Methods: DENALI-1 (NCT06682793) is a phase 1/2, open-label, nonrandomized study evaluating the safety and efficacy of A2B395 in adults. Patients are enrolled through BASECAMP-1 (NCT04981119), a master prescreening study that identifies patients with HLA LOH at any time in the course of their disease via next-generation sequencing (Tempus AI, Inc.). Key inclusion criteria include histologically confirmed recurrent unresectable, locally advanced, or metastatic cancers associated with EGFR expression, including colorectal, non-small cell lung, squamous cell head and neck, triple negative breast, and renal cell cancers. Patients must have received ≥1 line of prior therapy, such as a checkpoint inhibitor, molecular targeted therapy, or chemotherapy. The primary objective of phase 1 is to evaluate safety, tolerability, and the recommended phase 2 dose (RP2D) using a Bayesian optimal interval design for dose escalation. The dose-expansion phase will confirm RP2D and collect biomarker data. Phase 2 will assess overall response rate per RECIST v1.1. Clinical trial information: NCT06682793 .

Importance Circulating tumor human papillomavirus DNA (ctHPVDNA) is an important biomarker for the presence of HPV-associated oropharyngeal squamous cell carcinoma (OPSCC), but little is known about early postoperative kinetics of ctHPVDNA clearance. Objective To investigate early postoperative kinetics of ctHPVDNA in patients with HPV-associated OPSCC. Design, Setting, and Participants This prospective cohort study was conducted at a single tertiary care center from January 4, 2020, to January 26, 2023. Patients with newly diagnosed HPV-associated OPSCC undergoing surgical management were enrolled. HPV status was defined as positive if findings of p16 immunohistochemistry and/or HPV DNA in situ hybridization and/or E6/E7 RNA in situ hybridization were positive. Exclusion criteria included history of prior head and neck cancer and metastatic disease at presentation. Data were analyzed from September 1, 2024, to April 25, 2025. Exposures Transoral robotic surgery with concurrent neck dissection. Main Outcomes and Measures Blood was drawn prior to surgery (pretreatment), 1 to 2 days after surgery (postoperative days 1 to 2), and approximately 2 weeks after surgery (postoperative week 2; range, 8 to 20 days). ctHPVDNA was quantified by a tumor tissue–modified viral (TTMV) HPV DNA test. Correlations were tested between the pretreatment and postoperative day 1 to 2 TTMV HPV DNA levels using Gaussian regression. Concordance between detectability at postoperative day 1 to 2 and postoperative week 2 was explored using negative predictive value and positive predictive value. Results Of 57 included patients with detectable pretreatment TTMV HPV DNA, 51 (89%) were male, and the median (IQR) age was 59 (54-66) years. A total of 35 patients (61%) had blood draws at all 3 time points; 16 (28%) had detectable TTMV HPV DNA on postoperative day 1 to 2. Pretreatment and postoperative day 1 to 2 TTMV HPV DNA levels had a medium positive linear correlation ( r = 0.31; 95% CI, 0.04-0.54). Undetectable TTMV HPV DNA on postoperative day 1 to 2 blood draw had a negative predictive value of 0.95 (95% CI, 0.74-1.00) for an undetectable level on postoperative week 2 blood draw, but a detectable level on postoperative day 1 to 2 blood draw only had a positive predictive value of 0.19 (95% CI, 0.04-0.46). Of the 16 patients with detectable TTMV HPV DNA pretreatment and at postoperative day 1 to 2, only 3 (19%) continued to have detectable TTMV HPV DNA at postoperative week 2. One patient had undetectable levels at postoperative day 1 to 2 and detectable levels at postoperative week 2. Conclusions and Relevance In this study, ctHPVDNA detectability early after surgery did not predict detectability at 2 weeks after surgery. ctHPVDNA clearance early after surgery could predict a negative test at 2 weeks. A negative blood draw finding on postoperative day 1 may be used to omit a postoperative blood draw at 2 weeks for minimal residual disease detection in future clinical trials.

ABSTRACTBackgroundRecurrent squamous cell carcinoma (SCC) of the head and neck (SCCHN) remains a formidable clinical challenge despite available treatments. The phosphatidylinositol 3‐kinase (PI3K) pathway has been identified as a potential therapeutic target, and alpelisib, a selective PI3Kα inhibitor, has demonstrated efficacy in certain malignancies. Combining this targeted therapy with immunotherapy has been suggested in previous studies as a promising strategy to bolster the immune response against cancer.CasesA 69‐year‐old woman with locoregional recurrence of PIK3CA‐mutated SCC of the left maxilla and cervical nodal metastases. Several chemotherapeutic regimens, including cisplatin, docetaxel, 5FU, chemoradiotherapy, and mono‐immunotherapy, resulted in disease progression. Alpelisib combined with pembrolizumab led to a sustained response for 9 months. A 58‐year‐old man with recurrent metastatic PIK3CA‐mutated SCC of the oropharynx, involving the left lung, hilar, and mediastinal lymph nodes. Despite prior palliative radiation and platinum‐based chemotherapy with pembrolizumab and cetuximab, treatment with alpelisib and nivolumab resulted in a partial response. Severe hyperglycemia and rash led to treatment discontinuation.ConclusionOur findings highlight the potential of this innovative therapeutic combination, suggesting a need for further investigations in this setting.

Metastatic CUP is complex, especially NCUP. Precision oncology is crucial for rare, aggressive cancers. A 54-year-old had HER2+ neuroendocrine carcinoma of unknown origin. T-DXd treatment, response, re-challenge show importance of genomics and caution.