Rare Subtype Research Articles

Seco-iridoid glycosides and flavonoid glycosides from the Gentiana olivieri Griseb and their anti-inflammatory activities

Three undescribed seco-iridoid glycosides, one undescribed flavonoid glycoside, and three known glycosides were isolated and identified from Gentiana olivieri Griseb. The structures of these compounds were determined through spectroscopic analysis and ECD calculations. Olivierisecosides NP (1–3) were identified as aromatic conjugated seco-iridoid glucosides, among them olivierisecoside N was representing a particularly rare subtype known as the morroniside seco-iridoids. The compounds 2, 3, 5, and 6 exhibited significant inhibition of COX-2 expression, particularly compound 5 which demonstrated the most pronounced inhibitory activity with IC50 value of 23.33 ± 0.51 μM. This study provides evidence for the potential development and utilization of G. olivieri as a source of anti-inflammatory components.

Optimus-Era Dose Finding for Rare Cancers.

Advances in cancer biology and diagnostics have led to the recognition of a multitude of rare cancer subtypes, emphasizing the pressing need for strategies to accelerate drug development for patients with these cancers. This paper addresses the unique challenges of dose finding in trials that accrue small numbers of patients with rare cancers; strategies for dose optimization are proposed, in line with evolving approaches to dose determination in the age of the US Food and Drug Administration's Project Optimus.

Multiomic analysis in ovarian clear cell carcinoma to gain insight into biology and therapeutic opportunities.

e17540 Background: Ovarian clear cell carcinoma (OCCC) is a rare subtype with distinct histologic and molecular features. The prognosis of advanced/recurrent OCCC treated with standard of care surgery and platinum-based chemotherapy remains poor due to inherent chemoresistance. Therefore, there is an urgent need to identify novel biological insights and personalized treatment approaches to improve outcomes. Methods: Participants were referred to the SMMART Program at the OHSU Knight Cancer Institute. Archival or fresh tissue was obtained from metastatic sites and processed through a multiomics platform that included immunohistochemistry (Ki67, HER2, CD4, CD8, PD-L1), fluorescent in-situ hybridization, targeted next-generation sequencing panel (225 genes), whole transcriptomic sequencing, chromosomal microarray, and multiplexed analysis of 67 key cancer proteins and phosphoproteins on the Nanostring GeoMx Digital Spatial Profiler. Results: 5 participants were enrolled with an average age of 62 years (range 52-72). Therapeutically relevant findings included detectable HER2 expression by IHC (2+, N=2; 3+, N=2), HER2 amplification by FISH (N=2), and high HER2 and phospho-HER2 protein expression compared to a breast cancer cohort (phospho-HER2 supports active HER2 signaling in the tumor cells). Additional findings include TMB <10 muts/Mb (N=5), microsatellite stable (N=5), Ki67 40-60% (N=4), mild to moderate CD4 and/or CD8 infiltration (N=4), PD-L1 >1% (N=3), low homologous recombination deficiency score (N=4), chromosomal losses including ATM, SMAD4, RB1, and TP53, and single nucleotide variations in ARID1A (N=4). Two participants with HER2 expression were treated with off-label trastuzumab deruxtecan for 6 or 7 cycles yielding significant clinical benefit. Participant A (HER2 = 3+, FISH negative) had an exceptional response while Participant B (HER2 = 2+, FISH amplified) had stable disease. The toxicity profile was consistent with literature. Conclusions: Our OCCC cohort revealed elevated HER2 expression with or without genomic amplification in 4/5 cases. Two participants experienced clinical benefit when treated with trastuzumab deruxtecan, supporting further exploration of HER2 antibody drug conjugates in this aggressive disease. More study is needed to determine the frequency of HER2 overexpression and amplification in OCCC, the importance of HER2 on OCCC pathophysiology, and the therapeutic benefit of targeting HER2 in this population.

Overall survival and patterns of care for women with rare ovarian cancers: A prospective study from the Australian National Gynae-Oncology Registry (NGOR).

e17554 Background: Ovarian cancer (OC) is a heterogenous group of malignancies, most of which are rare. Data on patterns of care and survival of the most-rare sub-groups of OC (incidence rates < 6 per 100,000) in the real-world setting is limited. This study aims to describe patterns of care and overall survival (OS) for women with rare ovarian cancers in Australia. Methods: Clinical data were sourced from the NGOR and assessed for accuracy and completeness. High grade serous and endometrioid OC subtypes were excluded. Due to incompleteness of survival follow-up data, 3-year OS was only calculated for the state of Victoria. Results: Data on 2812 women with newly diagnosed OC from 2017-2023 within NGOR were collected and 716 women were subsequently identified with rare subtypes of OC. The 5 sub-types with the highest incidences were clear cell (n = 168, 23.4%), mucinous (n=151, 21.1%), adult granulosa cell (n=111, 15.5%), low grade serous (n=98, 13.7%) and carcinosarcoma (n=59, 8.2%). A further 23 additional rare subtypes included germ cell tumours and sex cord stromal tumours. The median follow-up time was 2.6 years and median age at diagnosis was 55 years. Most women had an ECOG 0-1 performance status (n=551, 77.0%). The primary treatment modality was surgery only (n=360, 50%), followed by surgery and systemic therapy (n = 317, 44.2%), systemic therapy only (n=28, 3.9%) and no treatment (n=11, 1.5%). Most women were discussed at a multi-disciplinary meeting (n=701, 97.9%). The diagnosis was confirmed on histology for all women. The 30-day post-operative adverse events (Clavien-Dindo >III severity) was 3.6 % (n=26), with the highest rate of post-operative events in the carcinosarcoma group of 12% (n=6). Using Fisher’s exact test across the 5 most common sub-types described above, there were significant differences in treatment modalities (p<0.001), rates of 30-day post-operative events (p=0.002), age adjusted charlson comorbidity index (p<0.001) and metropolitan versus remote regional status (p=0.007) between the sub-types. Survival at 3 years for these five sub-types of rare OC within the state of Victoria are summarised in the table. The highest 3-year OS was in adult granulosa and low grade serous sub-types. Conclusions: This is a large, real-world analysis of patterns of care and survival for women with rare sub-types of OC. Combining data with international sites will likely further enhance research on patterns of care and outcomes for women with rare OC. [Table: see text]

Primary Pulmonary Meningioma With Associated Multiple Micronodules: A Case Report With Comprehensive Diagnostic Overview

ABSTRACTBackgroundPrimary pulmonary meningioma (PPM) is an exceedingly rare neoplasm originating in the meninges within the lung. Despite sharing similarities with its central nervous system (CNS) counterparts, PPM presents unique diagnostic challenges and therapeutic considerations owing to its infrequent occurrence.CaseThis case report describes a 73‐year‐old male who underwent chest computed tomography (CT), which revealed a mass in the posterior basal segment of the right lower lobe, suggestive of a low‐grade malignant tumor approximately 30–40 mm in size. Single‐port video‐assisted thoracoscopic surgery (VATS) was performed to resect the mass via localized lesion excision (lung wedge resection). Intraoperative frozen section pathology indicated a low‐grade malignant epithelial tumor, leading to a decision for maximal lung function preservation, considering the patient's advanced age. The surgical team opted for a localized excision to ensure negative margins. Histopathological analysis confirmed the diagnosis of epithelioid PPM, a rare subtype even among PPM cases (World Health Organization [WHO] Grade I). The patient was discharged 9 days after surgery without complications and resumed normal daily activities 1 month postoperatively. The rarity of PPM precludes a standardized treatment protocol, with surgical resection as the primary approach. However, the efficacy of adjunctive therapies remains uncertain due to limited evidence.ConclusionThis case report contributes to a better understanding of PPM and emphasizes the importance of a comprehensive diagnostic evaluation and individualized treatment planning for this rare entity.

Patient Preferences for Treatment in Relapsed/Refractory Acute Leukemia in the United Kingdom: A Discrete Choice Experiment.

Acute leukemia is a cancer of the white blood cells which progresses rapidly and aggressively. There are two types: acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). The latter has a rare subtype: acute promyelocytic leukemia (APL). For some patients, following first-line treatment, remission is not achieved ("refractory disease"), and for others the leukemia returns after achieving remission ("relapse"). For these individuals, outcomes are typically poor. It is, therefore, important to understand patients' treatment priorities in this context. Building upon formative qualitative research, an online survey containing a discrete choice experiment (DCE) was designed to explore patients' treatment preferences in the relapsed/refractory setting. The DCE attributes were mode of administration; quality of life during treatment; chance of response; duration of response; and quality of life during response. Each respondent completed twelve scenarios containing two hypothetical treatments. Participants were eligible if they lived in the United Kingdom and had a diagnosis of acute leukemia. The data were analysed using a latent class model. A total of 95 patients completed the survey. The latent class analysis identified two classes. For both, chance of response was the most important attribute. For class 1, every attribute was important, whereas for class 2, the only important attributes were quality of life (during treatment and response) and chance of response. A greater proportion of respondents would fall into class 1 overall, and those with ALL or APL and those more recently diagnosed were more likely to be in class 2. Our results indicate that patients are strongly concerned about the chance of response, as well as quality of life (to a lesser extent), when faced with different treatment options in the relapsed/refractory setting. However, there is significant preference heterogeneity within the patient population, and other treatment characteristics also matter to many.

Evaluation of mixed response in tumor size and survival in patients with rare cancers treated with dual checkpoint inhibitor therapy (DART SWOG S1609).

2514 Background: RECIST criteria evaluate changes in tumor burden and have been utilized in cancer research for decades. Changes in the sum of maximum diameters of “target” lesions are used to designate patients into response categories, including complete response, partial response, stable disease, and progressive disease. However, not much is known about the implications of mixed response, where lesions within a patient show contrasting responses to systemic treatment. Here we evaluate the data from the Dual Anti-CTLA-4 and Anti-PD-1 Blockade in Rare Tumors (DART) SWOG S1609 to investigate the association between mixed response and survival among patients treated with dual checkpoint inhibitor therapy. Methods: A total of 796 patients were enrolled on the S1609 DART trial, a basket trial evaluating ipilimumab plus nivolumab across solid rare tumor subtypes. All patients had RECIST-measurable disease at the study entry. Patients were excluded from the analyses due to: ineligibility, n=47; not receiving any protocol therapy, n=23; death before day 65 (landmark for analysis based on first scan), n=86; 1 target lesion, n=153. Thus, 487 patients were analyzed. A 5mm cut-off for increase/decrease in lesions was used to define a mixed response. Cox regression models were used to evaluate associations between survival (landmarked at day 65, stratified by basket) and response category (reference of Stable Disease). Results: 6 groups were identified among the 487 patients: no lesions changed more than 5 mm (n = 105), all lesions increased more than 5mm (n = 69), all lesions decreased more than 5mm (n = 39), one+ lesion increased more than 5mm and one+ lesion decreased more than 5 mm (n = 24), one+ lesion increased more than 5mm and one+ lesion did not change more than 5 mm (either direction) (n =155), one+ lesion decreased more than 5mm and one+ lesion did not change more than 5 mm (either direction) (n =95). Hazard ratios and median survival (mOS) are shown (Table). Conclusions: This is the first evaluation of the association between mixed response and survival outcomes among patients with various tumors receiving dual checkpoint therapy. Our results suggest that survival outcomes are driven by the “worst” performing lesion; in other words, having an increase in any lesion is associated with worse outcomes, even if not all lesions increase. [Table: see text]

A retrospective, descriptive analysis of a single-center experience with patients with metaplastic breast cancer.

e13173 Background: Metaplastic breast cancer (MpBC) is a subtype of breast cancer (BC) that is commonly triple negative (TN) and chemotherapy (CT) resistant. Despite CT resistance, standard of care therapy is administered according to receptor status, regardless of metaplastic histology. Randomized data regarding optimal treatment of this rare histologic subtype are lacking. Methods: This was a retrospective analysis of MpBC patients (pts) treated at Miami Cancer Institute (MCI) between 2017 and 2021. Pts were identified using COTA real-world Analytics, an analytics platform enabling rapid investigation of longitudinal real-world data. Pt demographics, pathologic characteristics, staging, treatment, and survival outcomes were collected and analyzed. Results: 46 pts with MpBC were identified. Median age at diagnosis was 60.5 years, and 83.7% were post-menopausal. 84.8% were White, 10.9% were Black, and 54.3% were Hispanic (all White). 80.4% (n=37) had TNBC (ER < 1% and HER2 negative by ASCO CAP guidelines). 13.0% of pts (n=6) had spindle cell morphology and these pts had numerically lower 5-yr overall survival (OS) compared to those with non-spindle cell morphology; (83.3%; 95% CI 53.5%-100% vs 91.7%; 95% CI 82.7%-100%). Of 21 pts (45.7%) who underwent germline genetic testing, a pathogenic variant was detected in 2 (9.5%); (BRCA2, PALBB2). At diagnosis, 93.5% (n=43) had early-stage disease, 2.2% (n=1) had de novo metastatic breast cancer (MBC), 2 were unknown. Of the early-stage pts, 12 (27.9%) had stage 1, 19 (44.1%) stage 2, and 6 (14.0%) stage 3 BC. Of 43 pts with treatment records available, 34 (79.1%) received CT and 20 (46.5%) received anthracycline-based CT in the early-stage setting. Of those who received CT, 50% (n=17) were treated in the neoadjuvant setting, and 2 pts (11.8%) achieved pathologic complete response (pCR). Median distant recurrence free survival (DRFS) and OS were not reached in the overall cohort. Two-year OS was 90.5% (95% CI 81.6%-99.4%) and two-year DRFS was 78.9% (95% CI 66.6%-91.2%). Of the 43 pts with early-stage MpBC at diagnosis, 11 (25.6%) developed MBC with lung as the most common site of metastasis. Only 15.2% (n=7) of tumors underwent somatic mutation analysis and 71.4% (5/7) were PIK3CA-mutated. Of the pts who developed MBC, median progression-free survival with cytotoxic chemotherapy was 9.0 months (95% CI 5.0-13.0). Conclusions: MpBC represents an aggressive phenotype of BC and optimal guidance regarding treatment is lacking. Consistent with published literature, a high proportion of MpBC in this study were TN (>80%). Our dataset represents the largest cohort to date of Hispanic pts with MpBC. Despite the poor outcomes historically reported with MpBC, median DRFS and OS were not reached in this cohort, with short follow up. Further prospective randomized data on the optimal treatment of MpBC is warranted and a larger multi-institution review is planned.

Hematopoietic stem cell transplant for adults with mixed phenotypic acute leukemia.

6517 Background: Mixed phenotype acute leukemia (MPAL) is a rare acute leukemia subtype characterized by expression of lymphoid and myeloid lineage markers on blasts. Consequently, the role of hematopoietic stem cell transplant (HCT) consolidation is unclear. We conducted a retrospective study of MPAL patients treated at our institution integrating the impact of transplant status, chemotherapy, and initial response on survival. Methods: We evaluated patients with MPAL at Fred Hutchinson Cancer Center from 1/2005 – 9/2022, some of whom were previously reported (Huang et al, ASH 2023). Independent pathology review using 2022 WHO criteria verified MPAL diagnosis. Potentially transplant eligible patients were defined as those <75 years of age, diagnosed at least 6 months prior to data retrieval date, and alive 100 days after diagnosis with an evaluable induction response. Log-rank and Cox proportional hazard models were used to compare survival and adjust for baseline covariates. Survival was landmarked at 100 days. Results: Of 55 total patients, 42 were potentially HCT eligible and 30 received HCT (71.4%; 20/30 myeloablative). Patients who did not complete HCT were similar in age (median 46.2, range 18-70 vs median 50.3, range 24 – 74, p = ns) and had similar ECOG (ECOG 0-1 86.6% vs 75.0%, p = ns) at diagnosis. Nine of 12 non-transplanted patients had age-adjusted HCT-CI score ≤ 3. Patients receiving a HCT had better progression free survival (PFS) (p = 0.025) and were more likely to be alive at 48 months (61.6% vs. 32.4%, p = 0.011) with a median overall survival (mOS) of not reached (NR) (95% CI, 43 months – NR) compared to a mOS of 13 months (95% CI, 9 months – NR) for those not transplanted. Given that our prior work showed that the type of induction chemotherapy did not influence OS (p = 0.40) or remission status (p = 0.16) (Huang et al. ASH 2023), we investigated impact of remission status at the time of transplant. Differences in PFS and OS persisted when stratifying patients by induction response status with HCT status (PFS p = 0.0048; OS p < 0.0001). Patients who had a complete response (CR) followed by HCT had the longest mOS = NR (17 of 24 patients alive after 48 mo). Patients who had resistant disease (RD) and completed HCT had mOS = 43 months (95% CI, 43 months– NR). Patients who achieved CR but did not undergo HCT had mOS = 19 months (95% CI, 11 months – NR). Patients who had RD and did not undergo HCT had median OS of 6 months (95% CI, 6 – NR). The hazard ratio for death among patients who underwent HCT was 0.28 (95% CI 0.077 – 0.99, p = 0.049). Conclusions: HCT consolidation was significantly correlated with improved survival (p = 0.011). While potentially biased by selection and limited by small sample size, patients benefitted from undergoing a HCT regardless of response to prior therapy (p < 0.0001). This study suggests that patients with MPAL in CR after induction chemotherapy as well as those with less than complete responses should be considered for HCT consolidation.

ImmunoSarc II master trial (phase II of sunitinib and nivolumab): Results from the dedifferentiated chondrosarcoma (DDCS) cohort—A GEIS, ISG and UCL study.

11506 Background: Dedifferentiated chondrosarcoma (DDCS) is a rare aggressive CS subtype with a dismal prognosis and no standard of care systemic therapy. For those with advanced, metastatic disease, retrospective chemotherapy studies demonstrate short-term median progression-free survival (PFS) of around 3 to 5.5 months. Benefit from checkpoint and tyrosine kinase inhibitors has been reported, however clinical trial data is scarce, and endpoints are not well defined, thus benchmarking outcomes is challenging. The IMMUNOSARC I master-trial exploring sunitinib plus nivolumab in multiple sarcoma subtypes, detected potential activity in DDCS leading to a specific cohort within the phase II trial IMMUNOSARC II (NCT03277924). Methods: Patients (pts) with ECOG 0-1, centrally confirmed and progressive, measurable DDCS were eligible and treated with sunitinib 37.5 mg/d for 14 days (induction phase), followed by 25 mg/d, in combination with nivolumab 240 mg every 2 weeks until progressive disease (PD) or intolerance. Imaging assessments were performed every 8 weeks. Main endpoint was 6-m PFSR with one-arm survival design (type I error α 0.05, power 0.90, H0 40%, H1 70%) and a Brookmeyer-Crowley like test was assumed with at least 14 of 23 pts required without progression at 6 months. Results: Between December 2019 and October 2023, 24 pts with a median age of 60 years (38-76) were enrolled in 7 centres. Sixteen pts (66%), were male. Pts had received a median of 1 (0-2) prior lines of therapy. In total, 23 pts were evaluable with a median follow-up of 20.1 months (95%CI: 11.6-28.6). Median PFS, according to local site assessment, was 5.6 months (95%CI: 4.5-6.7); the 6m-PFSR was 10 of 23 pts (46%); (95%CI: 23-66) and median overall survival 10.3 months (95%CI: 6.7-13.9). In 19 pts with RECIST measurable response, 5 pts (26.3%) achieved a partial response; 10 (52.6%) stable disease and 4 (21.1%) PD. End-of-treatment reasons were PD in 21 pts (87%), toxicity 1 pt (4.2%) with two pts (8.4%) ongoing. For safety population, the most relevant study drug-related G3-4 toxicities were neutropenia (20.9%), anemia (16.7%), and increased ALT (12.5%). Conclusions: Sunitinib and nivolumab demonstrated encouraging activity in advanced DDCS that did not meet the primary endpoint, but compares favourably with previous analyses of cytotoxic and targeted therapy. The combination is worthy of further exploration in conjunction with reaching a consensus on clinically meaningful endpoints in this challenging population. Translational studies to identify potential predictive biomarkers are ongoing. Clinical trial information: NCT03277924 .

PD-1 inhibitors versus conventional therapies for adjuvant treatment of resected acral melanoma: A systematic review and meta-analysis.

e21555 Background: Acral melanoma (AM) is a rare and aggressive melanoma subtype with unique characteristics in western Caucasian population, but mostly prevalent in Asian population. FDA has approved pembrolizumab and nivolumab for the adjuvant treatment of melanoma. However, its role in AM is still unclear. In US and mainland of China, high-dose interferon alfa was once approved, while in other part of the world, there was no standard treatment for adjuvant therapy of AM. Thus, we performed a meta-analysis to summarize the efficacy of anti-PD-1 monotherapy in patients with AM in adjuvant setting and derive implications for early-stage AM management. Methods: A systematic review of electronic databases was conducted to identify studies that assessed relapse-free survival (RFS) and overall survival (OS) between adjuvant PD-1 and conventional therapy (interferon (IFN) / chemotherapy) or observation alone in patients with AM. RFS was the primary endpoint, OS was the secondary endpoint. We estimated RFS/OS using the fixed-effect model. Statistical analyses in our study were carried out using Stata 12.0 (Stata Corp LP, College Station, TX, USA). Results: Five retrospective studies that totally involving 516 patients with AM were recruited, including 3 China studies and 2 non-China studies. Among them, there were 260 PD-1, 74 IFN, 178 OBS and 4 chemotherapy, respectively. Adjuvant PD-1 inhibitor achieved better efficacy than conventional therapy, showing significant improvement both in RFS (HR 0.76, 95%Cl 0.61-0.95) and OS (HR 0.57 0.37-0.88). This trend of RFS/OS benefit was observed in all subgroups, includes control treatment (OBS/IFN) or study region (China/non-China). Conclusions: Our data supports that patients with resected AM are more likely to derive benefit from adjuvant PD-1 comparing to conventional treatment or observation alone. Perspective studies are warranted to explore the role of adjuvant PD-1 in AM. [Table: see text]

Clinicopathological features of hepatoid adenocarcinoma of the stomach: A multicenter retrospective study.

Hepatoid adenocarcinoma of the stomach (HAS) is a rare and aggressive subtype of gastric cancer (GC), accounting for less than 1% of all cases. It is characterized by frequent liver metastasis recurrence and a poorer prognosis than conventional GC. However, established treatment guidelines for HAS are currently not available.In this report, we present the results of a clinicopathological study of 19 patients diagnosed with HAS, including seven patients with liver metastasis, conducted by the Hiroshima Surgical Study Group of Clinical Oncology (HiSCO) between 2016 and 2018. The aim of the study was to retrospectively observe the outcomes of HAS with gastrectomy and hepatectomy for liver metastasis and determine relevant prognostic factor. We also examined the criteria and outcomes of hepatectomy for liver metastasis and aimed to suggest the optimal treatment for HAS, including chemotherapy. A total of 2147 patients underwent gastrectomy for GC at HiSCO-affiliated institutions during the study period; 19 patients, all male with a mean age of 70.9 years, were diagnosed with HAS by hematoxylin-eosin and immunohistochemical staining. Patients underwent gastrectomy at varying pathological stages: six at Stage I, three at Stage II, seven at Stage III, and three at Stage IV. Ten patients received postoperative chemotherapy and the 5-year survival rate was 67.7% after gastrectomy. Among the seven patients with pre or postoperative liver metastasis, five patients underwent hepatectomy. Although one patient had recurrence, the 3-year survival rate was 100% after hepatectomy. Contrary to previous reports suggesting a 3-year survival rate of approximmately 30% for HAS, our findings indicate that the prognosis for HAS may not be as poor as reported previously. This study contributes valuable insights into the management and potential treatment strategies for HAS.

Cytogenetic and molecular features of mixed-phenotype acute leukemia in US veterans and its potential impact on therapy.

e18535 Background: Mixed phenotype acute leukemia (MPAL) is a rare and heterogeneous subtype of acute leukemia. Per the 2022 WHO criteria, it is categorized based on its predominant immunophenotypic lineage (B vs. T) and the presence of a Philadelphia chromosome (Ph+) or a KMT2A rearrangement. While many other cytogenetic and molecular abnormalities have been described, due to the rarity of this disease, neither their incidence nor the role of targeted therapies has been well defined. We conducted a retrospective study of all veterans with MPAL diagnosed between 2000-2023 to examine the impact of different clinical, immunophenotypic, cytogenetic, molecular, and treatment strategies on overall survival (OS). Methods: Electronic medical record data from the Veterans Affairs Informatics and Computing Infrastructure database were used to identify 320 patients diagnosed with MPAL between 2000-2023 using the text utilization integration feature to query all notes. All patient charts were reviewed manually. Pathology reports and clinical notes were reviewed to collect data on diagnosis, treatment, and outcome. To date, 74 patients have been identified and included in this preliminary analysis. Cox regression analyses were used to compare OS between patients with different MPAL subtypes, cytogenetic, and molecular features as well as different treatment approaches. Multivariate analysis was performed with controls for age, race, and BMI. Results: In line with prior research, decreases in OS were seen among older patients > 65 yo compared to patients <30 yo and those who received an AML induction over ALL induction regimen with HR of 8.28 (p 0.04) and 2.02 (p 0.03) respectively. Patients who had a transplant had significantly improved OS with a HR of 0.19 (p <0.001). Of the 32 patients who had potentially targetable mutations, 14 received targeted maintenance therapy with either Ph+ or FLT3 inhibitors. Patients who got targeted maintenance therapy (including FLT3 inhibitors) had an OS of 55 months compared to 17 months for those who did not. 50% of those patients who did not get maintenance therapy went to transplant and 31% of patients who did get maintenance therapy went to transplant yet these patients still had improved OS. Conclusions: This preliminary data demonstrate that while MPAL is a complex and heterogeneous disease, a significant portion of patients have targetable mutations. Further studies evaluating targeted therapies such as FLT3, IDH, and menin inhibitors in MPAL patients may be warranted. [Table: see text]

Transcriptomic and epigenetic characterization of mucinous adenocarcinoma of the cervix.

e17518 Background: Mucinous adenocarcinoma of the cervix (MAC) is a rare and aggressive histologic subtype of cervical cancer with poorer prognosis than its more common counterparts, usual type endocervical adenocarcinoma (UEA) and squamous cell carcinoma (SCC). MAC is also known to be less responsive to standard chemotherapy and radiation approaches used to treat cervical cancer. In this study, we sought to identify transcriptomic and epigenetic features of MAC that distinguish MAC from UEA and SCC, and to identify features that may contribute to poorer prognosis in MAC compared to UEA and SCC. Methods: Clinical data, gene expression, miRNA expression, and methylation data for 17 MAC, 27 UEA, and 247 SCC from The Cancer Genome Atlas Cervical Cancer Project were obtained and analyzed. Clinical data were compared for the histologic groups using Fisher’s Exact, ANOVA, and Kruskal-Wallis statistics where appropriate. Kaplan-Meier curves were used for survival analyses. Gene expression data was analyzed using DESeq2 for differential expression of mRNA. Pathway enrichment analysis of gene expression data was completed using Qiagen IPA Core Analysis software. Comparative marker selection was used to determine differential expression of miRNA, and differential methylation across histologic subtypes. Analyses were completed both by histology and by disease-progression status. Data across all three platforms were integrated to evaluate for potential explanatory relationships of interest. Results: RNAseq analysis revealed a number of genes differentially expressed in MAC as compared to UEA and SCC. Several of these genes were also found to be differentially expressed in samples from patients with disease progression compared to those without known disease progression including increased expression of PPARGC1A, SLC2A1, and ZNF703 and decreased expression of NR4A3. Analysis also revealed hypomethylation at CpG probe sites mapping to SLC2A1 and decreased expression of miRNAs known to target SLC2A1 and PPARGC1A in MAC tumors . Pathways involving translation regulation, EIF2 signaling, and oxidative phosphorylation were downregulated in MAC whereas pathways involving mitochondrial dysfunction, glucose metabolism, and estrogen receptor signaling were upregulated in MAC. Downregulation of immune and inflammatory response pathways and upregulation of tumor-supporting macrophage activation was seen in MAC tumors with disease progression. Conclusions: We identified novel transcriptomic and epigenetic features and altered pathways in MAC, as well as those features and pathways associated with poorer prognosis in this population. These findings may contribute to further confirmatory research and lead to novel therapeutic strategies for this rare cancer.

The genetic risk architecture of mucosal melanoma.

10595 Background: Mucosal melanoma (MM) is a rare and aggressive subtype of melanoma. Outcomes for MM are significantly worse than for cutaneous melanoma (CM). While somatic mutations induced by UV radiation are known to cause CM, less is known about environmental and genetic alterations associated with MM. High penetrance alleles have been identified in familial cases of CM but the contribution of germline mutations to development of MM is not understood. Further, whilst population-based risk has been elaborated in CM, little is known for MM. The aim of this study is to characterize the germline genetic architecture of MM from high penetrance alleles to patient population genetics. Methods: A large retrospective cohort of MM patients (n=247) seen at MD Anderson Cancer Center were identified. Demographics, primary tumor sites, and presence of somatic mutations in BRAF, NRAS and KIT were extracted. Germline sequencing was performed on PBMC derived genomic DNA from the cohort using a gene panel of 322 major cancer genes. Frequency of identified germline alleles were compared to expected population control rate based on TOPMED using Fisher’s exact test. For genome wide association analysis (GWAS), genotyping will be performed on the MM cohort and the control group using the Infinium Global Screening Array. Cancer-free controls matched 3:1 based on MM cohort demographics have been assembled from existing case-control studies at MD Anderson. Following standard quality control procedures, we will impute variants from TOPMed using the Michigan Imputation Server. SNPtest v2.5.268 software will be utilized to perform association tests, using a multivariate logistic regression model incorporating gender and principal components. In addition to variants that may surpass a genome-wide significance score, we will inspect results for an enrichment of cancer genes. Results: Median age of MM cohort is 63, female predominant (60%), primarily White (84.6%), with gastrointestinal (36%), genitourinary (34%) and head & neck (30%) being the most common MM subtypes. Characteristics of the cohort were representative of the US MM population. Somatic mutations in KIT (26%) were most common. Germline mutations were found in 10.9% of the cohort, with most common detected variations in MITF (c.G952A:p.E318K) (2.4%) at OR of 13.9 (95%CI 5.0, 30.9), and CHEK2 (c.1100delC:p.T367fs) (1.6%) at OR of 16.4 (4.4, 42.9) compared to population control rate. Conclusions: Our study is the first to demonstrate the distribution of germline mutations in the largest cohort of MM patients. The MITF E318K allele is a known risk factor for CM, while CHEK2 1100delC allele has mixed evidence for conferring CM risk. GWAS data are currently being analyzed and these updated results will be presented in the context of the comprehensive analyses of germline risk alleles in MM patients.

High-grade surface osteosarcoma: A National Cancer Database study of demographic characteristics.

e23508 Background: High-grade surface osteosarcoma (HGSO) is an extremely rare malignant subtype of osteosarcoma. HGSO often affects long bones, particularly the femur, and is the rarest subtype of surface osteosarcomas. Though data is limited, current information suggests this cancer presents with a poor prognosis, generally affecting adults aged 20 to 40. Current treatment standards involve wide resection and chemotherapy. The National Cancer Database (NCDB) was examined to establish the demographic factors among HGSO patients and identify diagnostic and treatment trends. Methods: A retrospective cohort study from 2005-2020 was conducted using the NCDB. A total of 99 patients were found with a histologically confirmed diagnosis of high-grade surface osteosarcoma (ICD-9194-3). Factors such as gender, age, race, insurance status, rural/urban residence, treatments, mortality rates, and Charles/Deyo scores were analyzed using descriptive statistics, and trends in incidence were interpreted via regression analysis. Results: Yearly HGSO incidence rates increased from 2005 to 2020 (R2 = 0.19). The average age of diagnosis was 41 years (SD = 24.9, range = 10-90) with men diagnosed (54%) slightly more than women. The majority of patients were non-Hispanic white (73%), had private insurance (55%), and lived in a metropolitan area with over 250,000 in population (89%). The average patient was diagnosed at a hospital 40.4 miles away from their home (SD = 84.9, range 0.4-648.4 miles). Most patients (55%) were in stage II at diagnosis, and 86% of patients had a Charlson-Deyo comorbidity score of 0. The most common primary site of this malignancy was the long bones of the lower limb and associated joints (67%), while the upper extremities (8%) and pelvic bone (8%) served as less common primary sites. Surgery was the most common primary treatment (62%). Data from 69 patients revealed the 90-day mortality post-surgery was 3%. The mean survival rate was 70% at two years and 52% at five years. Conclusions: To the best of our knowledge, this study represents the first NCDB analysis of HGSO. Our analysis demonstrated that HGSO occurs most often, but not exclusively, within the lower extremity long bones, which may be an important diagnostic distinction. It was previously indicated that the average age at HGSO diagnosis is 20-40 years, but our analysis suggested it is closer to 40. Our analysis revealed a five-year survival rate of 52% which is worse than prior studies have indicated. Demographic data has revealed the majority of patients were non-Hispanic white, privately insured, and living within a metropolitan area. This trend may suggest access to healthcare resources is influencing this cancer’s diagnosis and treatment. Further research is warranted to explore whether the demographic patterns seen in HGSO are indicative of biological causes or socioeconomic factors that are significantly influencing diagnosis.

Descriptive analysis of brain metastases (BM) of solid neoplasms in an academic hospital from a low- and middle-income country (LMIC) with a Hispanic population.

e14015 Background: Multidisciplinary management of BM of solid cancers integrates different combinations of treatment modalities. The scarcity of SRS centers has prevented widespread adoption of this therapy for appropriately selected patients. Methods: One-hundred eighteen (51.7% female, 48.3% male, median age 59 years) BM patients from a National Health Institute from Mexico (INCMNSZ) were included and analyzed. Results: The most common primary tumors were lung and breast cancers (25 cases each, representing 21% of the whole cohort), kidney cancer (14%), male germ cell tumors (10%), metastatic carcinoma of unknown primary (CUP) (5%), upper- and lower- gastrointestinal cancers (5%), thyroid differentiated cancers (5%), followed by melanoma, prostate, ovarian, hepatobiliary cancers and sarcoma (3% each of them) and urothelial carcinoma (2%) being the least common. No biopsy was reported for only one case. The most common histomolecular tumors were adenocarcinoma of the lung (17 cases), renal cell carcinoma (17), triple negative (TN) breast cancer (BC) (9), HER-2+ BC (7), Nonseminomatous germ cell tumor (7), CUP (6), ER+/HER-2+ BC (5), Germ cell tumor with choriocarcinoma (5), small-cell lung cancer (SCLC) (5), melanoma (5), prostate adenocarcinoma (5), thyroid differentiated cancer not otherwise specified (NOS) (5). Rectal adenocarcinoma, high-grade serous ovarian cancer, ER+/PR+ BC, sarcomas and NSCLC (3 cases, each) and urothelial carcinoma (2). Rare tumor subtypes, with one case, each included hepatocellular carcinoma, PR+/HER2+ BC, follicular thyroid cancer, esophageal, gastric and colonic adenocarcinomas, neuroendocrine prostate, neuroendocrine gallbladder, endometrial, large cell neuroendocrine lung carcinomas and cholangiocarcinoma. A solitary BM was present in 44 patients (37.3%), 2-3 BM in 30 (25.4%) and >3 BM in 44 patients (37.3%). 18 patients (15.2%) were not symptomatic at the time of diagnosis. 79 patients were treated with Whole-Brain Radiotherapy (WBRT), ten with a combination of surgery and adjuvant WBRT, seven with surgical resection without radiotherapy, only five included SRS as part of their treatment and seventeen received only supportive care. There was no difference in overall survival (OS) between treatment modalities excluding supportive care (p=0.05). Conclusions: Our experience from a LMIC with Hispanic population highlights that more than 50% of BM metastasize from solid tumors different from lung and breast cancers. Even though SRS has been included in recent guidelines from ASCO and ESMO, WBRT is the option most commonly included in multimodality treatments.

Curative Approaches for Metaplastic Breast Cancer: A Retrospective Cohort Outcome Review

BackgroundMetaplastic breast cancer (MBC) is a rare and heterogeneous breast cancer subtype, and there are critical gaps in our understanding of its long-term outcomes. This retrospective cohort study aimed to address these gaps by scrutinizing the pathological and clinical aspects of MBC to enhance clinical decision-making and refine patient care strategies. MethodsThis registry-based retrospective cohort study included females aged ≥21 years diagnosed with MBC or matrix-producing carcinoma. The data were obtained from January 2001–August 2020 from the XXXX Registry of XXXX, which included 23,935 patients. Demographic and clinicopathological characteristics, neoadjuvant chemotherapy responses, and survival outcomes were analyzed. Statistical assessments involved univariate and multivariate Cox proportional hazards models and Kaplan–Meier survival analyses. ResultsThis study enrolled 170 patients; 87.1% had non-metastatic disease and 12.9% had metastatic disease. The age of patients at diagnosis ranged from 46 to 65 years (median, 56 years). The cohort's predominant characteristics were advanced clinical stage (77.6%), node negativity (67.6%), and grade 3 disease (74.1%). In patients receiving curative intent treatment, neoadjuvant chemotherapy yielded a pathological complete response of 19.2% and a disease progression rate of 46.2%. Multivariate analysis showed that adjuvant radiation therapy significantly improved overall survival (OS) and disease-free survival (DFS), with hazard ratios (HRs) of 0.29 (95% confidence interval [CI], 0.13 – 0.62; p < 0.005) and 0.23 (95% CI, 0.10–0.50; p < 0.005), respectively. Clinical T3 and T4 stages, and nodal involvement were associated with poor outcomes. Stable disease after neoadjuvant chemotherapy was associated with poor OS and DFS. Conclusion(s)This study sheds light on the complex landscape of MBC and emphasizes the pivotal role of adjuvant radiotherapy in enhancing patient outcomes. Despite advancements, challenges persist that warrant continued research to refine neoadjuvant chemotherapy strategies and delve into the nuanced factors that influence treatment responses.

Efficacy and safety of SHR-2554 in advanced epithelioid sarcoma: A phase 2 trial.

11549 Background: Epithelioid sarcoma (ES) is a rare and aggressive subtype of soft-tissue sarcoma. The loss of SMARCB1 (INI1) expression which leads to oncogenic dependence on the transcriptional repressor EZH2 has been observed in over 90% of ES. Patients (pts) with metastatic ES have a poor prognosis. We investigated the efficacy and safety of SHR-2554, an oral selective EZH2 inhibitor, in pts with refractory ES. Methods: To be eligible for inclusion, pts had to fulfill the following criteria: 8 years or older; histologically confirmed advanced or metastatic ES with loss of INI1 or upregulated mRNA level of EZH2; progressive disease after at least one line of doxorubicin-containing chemotherapy; the presence of measurable disease according to RECIST 1.1; an ECOG performance status of 0-1. Pts received SHR2554 (350 mg, bid, po) until disease progression or unacceptable toxicity. The primary endpoint was progression-free rate at 12 weeks. A Simon two-stage design was applied. If there were 3 pts remaining progression-free at 12 weeks within the first 9 pts, the cohort would expand to 17 pts and the outcome would be positive if more than 7 pts remained progression-free at 12 weeks. Results: Between Jul 2021 and Dec 2023, a total of 17 pts were enrolled and received at least 1 dose of SHR-2554. The median age was 32 years (range 8-57) and 41.2% were males. 9 (52.9%) pts had received immunotherapy targeting PD-1/L1 and 6 (35.3%) pts had received anti-angiogenesis therapy before enrollment. The median line of previous treatment was 2 (range 1-4). Loss of INI1 was confirmed in 14 (82.4%) pts. Tumor response was evaluated in 14 pts at data cutoff. 9 (64.3%) of 14 pts remained progression-free at 12 weeks. The primary endpoint was met. Based on investigator assessment, 3 (21.4%) of 14 pts achieved partial response and 8 (57.1%) pts had stable disease as best response. Adverse events (AEs) were generally mild. The most common treatment-related hematological AEs were anaemia, platelet count decreased and hyperuricaemia. Conclusions: SHR-2554 showed promising efficacy and an acceptable safety profile in pts with refractory ES, warranting further investigation. Clinical trial information: ChiCTR2100046099.

Efficacy of systemic treatments in patients with metastatic lung invasive mucinous adenocarcinoma.

e20609 Background: Invasive mucinous adenocarcinoma (IMA) is a relatively rare histological subtype of lung adenocarcinomas that differs in its clinical behavior, radiologic features, histopathological, and genomic characteristics than invasive non-mucinous adenocarcinomas (INMA). Methods: We retrospectively investigated medical records of patients diagnosed with lung IMA at four oncology centers in Turkey. Patients who were ≥18 years of age, pathologically diagnosed with lung IMA, and who received at least one course of treatment for metastatic or inoperable disease were included in the study. Results: Forty-one patients were included in the study. The median follow-up was 16.6 months. Among the included patients, 24 (58.5%) were male, 17 (38.5%) were female, and their average age was 62. Six (14.6%) patients had a targetable mutation. Three (7.3%) patients were epidermal growth factor receptor (EGFR), two (4.8%) anaplastic lymphoma kinase (ALK) mutation, and one (2.4%) neurotrophic tyrosine receptor kinase (NTRK2) fusion. Most patients (83.1%) had received platinum-based chemotherapy as a first-line treatment. Of the patients who received cytotoxic chemotherapy, 9 (25.7%) had a partial response, 14 (40%) had a stable response, and 12 (34.3%) had progression. The median PFS was 8.24 months (95% CI: 5.9-10.5 months), and the median OS was 20.4 months (95% CI: 14.4-26.3 months) in all study populations. In those receiving cytotoxic chemotherapy, median PFS and OS were 8.11 months (95% CI: 5.02-11.2) and 17.5 months (95% CI: 11.7-23.3 months), respectively. While the PFS of two EGFR-positive patients were similar at 18.9 months and 20.6 months, the third patient's PFS was quite prolonged (66.5 months). The ALK-positive patients receiving brigatinib and crizotinib PFS were 15.8 months and 2.73 months, respectively. The PFS of the patient receiving entrectinib was only two months. Among the entire patient population, only one patient used oxaliplatin and capecitabine combination (XELOX) as chemotherapy. In this patient, who progressed after four cycles of gemcitabine and platinum first-line treatment, a partial response and 7.23 months PFS were achieved with second line XELOX. Conclusions: Standard-of-care treatments have the same efficacy in IMA and INMA patients. Targetable mutation is less common in IMA patients compared to INMA. 5-FU-based chemotherapies also appear to be effective in lung IMA patients.