Hallemeier, Christopher Leigh

Objectives: For locally advanced rectal adenocarcinoma (R-ACA), a nonoperative management (NOM) approach has emerged as a guideline-supported treatment option. However, the variables associated with NOM receipt are unknown. Methods: Utilizing the National Cancer Database, we performed a retrospective cohort study of adults with stage 1 to 3 R-ACA managed with curative intent from 2004 to 2018. The primary outcome was the proportion of patients receiving NOM versus surgery. The secondary outcome was survival among NOM patients. Results: A total of 128,297 patients were included. In all, 115,888 (90.3%) received surgery and 12,409 (9.7%) received NOM. Receipt of NOM was associated with age above 70, Charlson-Deyo score of 0, race (Black, Asian or Pacific Islander, or other vs. White), insurance status, geographical region, treatment in a community facility, year of diagnosis (2012-2018 vs. 2004-2011), tumor grade 1 versus ≥ 2, clinical T-stage ≥ 2, and clinical N1 or N2 versus N0. In the NOM cohort, poorer overall survival was associated with age 70 and above, male sex, Charlson-Deyo score ≥ 1, insurance status, geographical region, rural urban density versus metro/urban, treatment in a community facility, year of diagnosis (2004-2011 vs. 2012-2018), clinical T4 versus T1, clinical N1 or N2 versus N0, grade 3 versus 1, treatment with a radiotherapy dose <45 Gy versus 45 to 54 Gy, and omission of chemotherapy. Conclusions: Several demographic factors and social determinants of health were associated with receipt of NOM and overall survival. With the increasing utilization of NOM, it will be important to understand the drivers of treatment decisions and influences on access to the desired treatment approach.

ABSTRACT Background Multimodality therapy incorporating a combination of cytoreductive surgery (CRS), intraperitoneal (IP) and systemic therapy continues to evolve for peritoneal carcinomatosis (PC) However, treatment and outcomes vary depending on tumor of origin. Aims To develop Appropriate Use Criteria (AUC) guidelines to facilitate treatment decision‐making for patients with PC based on available evidence. Materials and Methods The American Radium Society (ARS) multidisciplinary expert panel performed a comprehensive systematic review. Preferred Reporting Items for Systematic Reviews and Meta‐analyses (PRISMA) methodology was used. These studies were used to inform the expert panel, which then rated the appropriateness of various treatments in seven representative clinical scenarios through a well‐established modified Delphi consensus methodology. Results Treatment of PC is often treated with a combination of CRS and IP ± systemic chemotherapy but specific recommendations exist for different tumor types and outcomes vary. Discussion Treatment of PC is complex and varies depending on origin of primary tumor and extent of disease. These AUC assist in patient and treatment selection for different clinical scenarios. Conclusion A summary of recommendations is outlined to guide practitioners on the management of PC from different tumor origins.

Objectives: Esophageal cancer (EC) often presents with dysphagia due to tumor obstruction. Esophageal stenting has the potential of palliating dysphagia, improving nutrition, preventing aspiration, and improving quality of life (QoL) but may be associated with risks. The present systematic review and guidelines are intended to assist treatment decision-making when considering stent placement in patients with EC based on the available evidence. Methods: Using the population, intervention, comparator, outcome, timing and study design framework, the evidence was assessed using Cochrane and PRISMA 2020 methodology. Eligible studies included prospective phase II-III trials and retrospective analyses published between January 1, 2010 and December 3, 2024 in the Ovid Medline database. These references were assessed by American Radium Society (ARS) Appropriate Use Criteria (AUC) methodology. RAND-UCLA consensus methodology was used to rate the appropriateness of the use of stents. Results: ARS AUC recommendations include (1) esophageal stenting is usually not appropriate in patients with early-stage EC in whom upfront surgery is planned; (2) esophageal stenting is usually not appropriate in patients with locally-advanced EC in whom neoadjuvant/perioperative therapy and esophagectomy or definitive chemoradiation is planned; (3) esophageal stenting may be appropriate in the setting of metastatic EC, especially in patients with short life expectancy with limited treatment options; (4) esophageal stenting is usually not appropriate for benign stricture following curative-intent therapy; (5) esophageal stenting is usually not appropriate for locally recurrent tumor in the setting of prior radiation; and (6) esophageal stenting is usually appropriate for management of tracheoesophageal fistula before curative-intent treatment. Conclusions: This ARS AUC summary provides guidelines for the use of esophageal stents in patients with EC provides based on available evidence.

Objectives: This practice parameter was revised collaboratively by the American College of Radiology (ACR), and American Radium Society (ARS). Image-guided radiation therapy (IGRT) uses various imaging modalities to maximize the accuracy and precision of radiation treatment delivery. Methods: This practice parameter was developed according to the process described under the heading The Process for Developing ACR Practice Parameters and Technical Standards on the ACR website (https://www.acr.org/Clinical-Resources/Practice-Parameters-and-Technical-Standards) by the Committee on Practice Parameters–Radiation Oncology of the ACR Commission on Radiation Oncology in collaboration with the ARS. Results: This practice parameter for IGRT addresses qualifications and responsibilities of personnel, clinical IGRT implementation, documentation, quality control and improvement, safety, and patient education. Since the publication of the ACR–ASTRO Practice Parameter in 2019, there is now more clarity as to what criteria and parameters need to be documented in the medical record, a better appreciation of the large amount of imaging data, how to interpret such data, as well as the complex interactions of multiple systems in the implementation of IGRT. Conclusions: This practice parameter assists practitioners in the clinical use of IGRT. IGRT should complement and be used in combination with other quality assurance processes. IGRT is a rapidly evolving field, and practitioners should have a thorough understanding of its strengths and potential limitations.

e14551 Background: Extracellular vesicles (EVs) are microscopic particles released by all cell types with a distinct fingerprint reflecting the cell of origin. In patients with prostate cancer, PSMA+EVs have been associated with clinical outcomes. In this study, we investigated tumor-derived EVs (tdEVs) using the tumor-specific CD326 marker as a novel biomarker for pancreas ductal adenocarcinoma (PDAC). Methods: The study included patients with localized PDAC treated on a prospective phase 2 clinical trial evaluating a 15-fraction chemoradiation (CRT) regimen. Blood samples were obtained after induction chemotherapy (C) (prior to CRT) and in follow-up. 20 healthy controls were included. High-resolution flow cytometry enumerated levels of fluorescent antibody labelled tumor-specific CD326 (EpCAM)-positive EVs. All samples were de-identified and randomly coded. The technologist responsible for EV analysis was blinded to patient information and clinical data. Each sample was run in triplicate. Flow cytometry data was analyzed with custom-built software to automatically determine and apply gates and generate reports with scatter plots and EV concentrations for each combination of markers and data summaries. Results: tdEV data were analyzed from 70 patients with pre-CRT samples. Patients had mean age 66 years (9.0 standard deviation), with 60% ECOG 0, 43% borderline resectable and 48% locally advanced. Patients had a median 8 cycles of C prior to CRT, and 70% proceeded to surgery after CRT. 2-year overall survival (OS) was 54%. Patient samples showed elevated total CD326 EVs compared to the healthy controls (p = 0.0005). Furthermore, patient CD326 EVs revealed two distinct subpopulations: small (120-1,000nm) and large (1,000-3,000nm) size CD326 EVs. No large CD326 subpopulation was found in healthy donor samples. Higher pre-CRT levels of total CD326 and large CD326 EVs were associated with decreased progression-free survival (PFS) (hazard ratio (HR) = 2.38, p = 0.013 and HR = 2.017, p = 0.021) on multivariable models with surgical resection. Resection was associated with increased PFS (p < 0.0001), and the interaction terms did not meet significance (p = 0.083 and p = 0.21). No differences in pre-CRT total or large CD326 EVs were identified between patients with or without surgical resection (p = 0.72 and p = 0.83). CA19-9 levels were not predictive of clinical outcomes in this trial and showed no association with EV levels. Conclusions: We present an association between clinical outcomes and tdEVs in PDAC, highlighting their potential as a novel, independent biomarker. If validated, tdEVs may offer an opportunity to personalize care and improve risk stratification.

Objectives: Cervical esophageal cancer (CEC) is an uncommon malignancy accounting for <5% of all esophageal carcinomas. Treatment of CEC varies and is adapted from established regimens used for squamous cell carcinoma (SCC) or the lower esophageal and head and neck. The present systematic review and guidelines are intended to assist treatment decision making for patients with CEC based on the available evidence. Methods: Using the Population, Intervention, Comparator, Outcome, Timing, and Study Design (PICOTS) framework, the evidence regarding treatment outcomes was assessed using Cochrane and PRISMA 2020 methodology. Eligible studies included prospective Phase II to III trials and retrospective analyses published between January 1, 2013 and February 23, 2024 in the Ovid Medline database. These references were assessed through the American Radium Society (ARS) Appropriate Use Criteria (AUC) methodology. A systematic review PRISMA 2020 checklist confirmed the completion of essential elements. RAND-UCLA consensus methodology was used by the expert panel to rate the appropriateness of the treatment options. Results: ARS AUC recommendations include (1) larynx preservation using endoscopic resection (EMR or ESD) alone for the typical case with pT1a cN0 cM0 CEC, (2) definitive CRT for the typical case with cT1bN0M0 in patients who cannot undergo endoscopic resection, (3) larynx-preserving using definitive CRT (with or without induction chemotherapy) for the typical case with nonmetastatic locally advanced CEC (advanced T-stage tumors or involved lymph nodes), with surgery reserved for those patients with incomplete response or locoregional recurrence. Conclusions: This ARS AUC summary provides guidelines for the management of SCC of the cervical esophagus provides based on available evidence. Topics that warrant further investigation include optimization of (1) patient selection; (2) multimodality therapies including chemotherapy, immunotherapy, and targeted agents; (3) radiation dose, schedule, and treatment volume; and (4) supportive care for patients with CEC. Ongoing trials continue to improve outcomes for patients with CEC.

84 Background: Local therapies potentially offer a curative approach for patients with oligometastatic colorectal cancer (CRC). The effectiveness of systemic chemotherapy following definitive local treatment in this setting is not well-defined. Tumor-informed circulating tumor DNA (ctDNA) might guide management strategies after curative-intent local treatment. Methods: This is a single institution retrospective study of patients with CRC who underwent curative-intent local therapy to an isolated site of metastatic disease and had post-intervention tumor-informed ctDNA (Signatera) testing. The study was approved by the institutional review board. Clinical characteristics, including ctDNA results, were collected and evaluated. Kaplan-Meier method and log-rank test were used to calculate and compare disease-free survival (DFS). Factors associated with DFS were analyzed using multivariate Cox proportional hazards model. Results: 45 patients were included with median age of 59 years, 62% being male, 91% white, and 53% with stage IV disease at diagnosis. 37% of the patients had RAS mutations, no patient had BRAF mutation, and 2.2% patient had mismatch repair deficient disease. Isolated liver metastases were present in 80% of patients, lung metastases in 11% and other sites in 9%. 44 patients received chemotherapy prior to definitive treatment, with a median treatment duration of 16 weeks. ctDNA tests were done prior to local therapy in 23 patients, with 14 cases (61%) testing positive. Definitive treatment included resection (58%), ablation (13%), radiotherapy (4%), and multimodality (25%). Post-definitive treatment chemotherapy was administered to 24 (53%) patients. ctDNA positivity following definitive therapy was observed in 10 patients (22%), which was associated with a poorer prognosis, with a median DFS of 5.3 months compared to 21.3 months for the ctDNA-negative group (p<0.001). These findings were confirmed on multivariate analysis. In patients who had negative ctDNA after definitive local treatment, median DFS was 14.9 months for those who received post-intervention chemotherapy versus 21.3 months for those without post-intervention chemotherapy (p=0.835). Conclusions: Patients with negative ctDNA results following definitive local therapy for isolated metastatic CRC have better prognosis. Post-intervention chemotherapy in this group of patients was not associated with improved DFS. ctDNA guided omission of post-intervention chemotherapy following curative-intent local treatment of oligometastatic CRC warrants further study. [Table: see text]

(1) Background: Local therapies offer a potentially curative approach for patients with oligometastatic colorectal cancer (CRC). An evidence-based consensus recommendation for systemic therapy following definitive locoregional therapy is lacking. Tumor-informed circulating tumor DNA (ctDNA) might provide information to help guide management in this setting. (2) Methods: A multi-institutional retrospective study was conducted, including patients with CRC that underwent curative-intent locoregional therapy to an isolated site of metastatic disease, followed by tumor-informed ctDNA assessment. The Kaplan–Meier method and log-rank tests were used to compare disease-free survival based on ctDNA results. ctDNA test performance was compared to carcinoembryonic antigen (CEA) test results using McNemar’s test. (3) Results: Our study cohort consisted of 87 patients treated with locoregional interventions who underwent ctDNA testing. The initial ctDNA test post-intervention was positive in 28 patients and negative in 59 patients. The median follow-up time was 14.0 months. Detectable ctDNA post-intervention was significantly associated with early disease recurrence, with a median disease-free survival (DFS) of 6.63 months compared to 21.30 months in ctDNA-negative patients (p < 0.001). ctDNA detected a numerically higher proportion of recurrences than CEA (p < 0.097). Post-intervention systemic therapy was not associated with improved DFS (p = 0.745). (4) Conclusions: ctDNA results are prognostically important in oligometastatic CRC, and further prospective studies are urgently needed to define its role in guiding clinical decisions.