Shi, Qian

Abstract Background Synthetic control arms (SCAs) derived from historical trial data can complement randomized controlled trials (RCTs), particularly in oncology where feasibility, ethical, and cost constraints may limit conventional trial designs. However, their validity for overall survival (OS) remains uncertain. We evaluated the feasibility and limitations of constructing SCAs from the ARCAD metastatic colorectal cancer (mCRC) database across multiple treatment lines. Methods Seven landmark RCTs representing first-, second-, and third-line settings were selected. External control arms were constructed from ARCAD individual patient-level data using propensity score matching based on key clinical and biological variables from a validated ARCAD prognostic score, with adjustment for geographic region and time era when needed. A prespecified two-step benchmarking framework assessed: (1) control-arm OS reproducibility and (2) virtual trial comparisons between matched synthetic controls and original RCT experimental arms. Agreement was evaluated using hazard ratios (HRs) and Z-tests. Results A total of 28,022 patients met the inclusion criteria. ARCAD-derived SCAs were successfully constructed for all selected RCTs and closely reproduced control-arm OS. After matching, baseline characteristics were well balanced, with minimal differences between included and excluded patients. Virtual trials showed concordant treatment-effect estimates with the original RCTs, with a median absolute HR deviation of 0.05 and no significant differences by Z-tests (P>.05). Survival outcomes were consistently reproduced across treatment lines. Conclusion ARCAD-derived SCAs reliably reproduced control-arm OS and benchmark treatment-effect estimates from landmark RCTs in mCRC. Despite limitations related to residual confounding and missing data, this framework supports benchmarking, trial design, and exploratory analyses when conventional control arms are impractical.

Abstract Purpose Traditional adverse event (AE) reporting in oncology trials focuses on the single worst CTCAE grade, which may underrepresent chronic or recurrent toxicity burden. We applied a longitudinal toxicity framework to compare toxicity profiles of chemotherapy with or without cetuximab in metastatic colorectal cancer. Patients and Methods We pooled two randomized first-line trials in the ARCAD database. AEs examined were diarrhea, rash, hand-foot syndrome (HFS), fatigue, anorexia, and mucositis. Outcomes included grade ≥3 AE, time to first occurrence of maximum grade, early onset (≤6 weeks), and AEL, a normalized measure of cumulative toxicity burden over treatment. Analyses were adjusted for chemotherapy backbone, ECOG performance status, sex, primary tumor location, dose reduction, and treatment duration. Results Compared with Chemotherapy alone (n = 564), Chemotherapy plus cetuximab (n = 738) was associated with higher grade ≥3 rash (21% vs 0.5%; adjusted odds ratio [OR] 49.89, 95% CI 15.8–157.4), higher rash AEL (0.257 vs 0.069; adjusted mean difference 0.22, 95% CI 0.21–0.23), and more frequent early-onset maximum rash (67% vs 34%; adjusted OR 4.28, 95% CI 2.72–6.74). Rash AEL remained higher with cetuximab within maximum-grade strata. HFS showed higher grade ≥3 risk and overall AEL with cetuximab, but no within-grade AEL difference, indicating higher overall HFS burden reflected grade distribution rather than within-grade chronicity. No consistent differences were observed for other AEs. Conclusions Incorporating onset timing and AEL distinguished persistent toxicity burden from isolated peak events. This framework may support comparative tolerability assessment when chronic toxicity burden is central to decision-making.

PURPOSE Adherence to operative standards and thorough documentation of surgical technique are critical, particularly in multidisciplinary clinical trials. We sought to evaluate variability in the performance and documentation of oncologically relevant aspects of technical surgery among patients enrolled in Alliance A021501, a phase 2 National Clinical Trials Network randomized clinical trial of neoadjuvant therapy for borderline resectable pancreatic adenocarcinoma. METHODS We reviewed the primary operative and pathology reports of all enrolled patients who underwent complete pancreatic resection. Operative techniques and pathologic end points with potential to influence recurrence and survival were evaluated. RESULTS Fifty-one of 126 study participants (40.5%) underwent complete pancreatectomy. The extent of lymphadenectomy was documented in 36 (70.6%) operative reports, and 5 (9.8%) reports outlined the specific lymph node stations removed. Periadventitial dissection of the superior mesenteric artery was described in 25 of 50 (50.0%) operative reports. Immediate histopathologic analysis of the hepatic duct and pancreatic parenchyma margins was documented in 29 of 50 (58.0%) and 32 of 49 (65.3%) reports, respectively, and presence or absence of residual disease following resection was documented in 9 of 51 (17.6%) reports. Specimen orientation was documented in 19 of 51 (37.3%) pathology reports, and 30 of 49 (61.2%) pathology reports stated the distance between the tumor and final SMA margin. CONCLUSION Even in this rigorously controlled, multicenter, randomized pancreatic cancer clinical trial, performance of key elements of technical surgery was inconsistent, and documentation was incomplete. Standardization of technique and documentation in clinical trials and within clinical practice should be addressed to improve quality assurance and trial interpretability.

Abstract Purpose: Pancreatic ductal adenocarcinoma (PDAC) frequently recurs after neoadjuvant therapy (NT) and curative-intent resection. Although major pathologic response predicts favorable outcomes, most patients achieve only minor response with a heterogeneous recurrence risk. We asked whether the spatial organization of residual PDAC encodes clinically relevant biology beyond residual tumor burden. Experimental Design: In a retrospective cohort of 203 patients with resected PDAC treated with NT and restricted to minor pathologic response, routine hematoxylin and eosin (H&E) whole-slide images were segmented into cancer and stroma using an artificial intelligence–enabled pipeline. Spatial composition (patch density, edge density) and configuration (compactness/complexity, intermixing) were quantified and tested for associations with disease-free survival (DFS) using multivariable models adjusted for standard clinicopathologic factors. Results: Shorter DFS was associated with a fragmented, interface-rich tumor–stroma ecology featuring higher edge density and diversity and reduced homotypic aggregation, independent of clinicopathologic variables. Two spatial risk models were independently prognostic: (i) cancer mean shape index plus stromal shape index variability [adjusted hazard ratio (HR), 1.71; P = 0.003] and (ii) mean stromal patch area plus edge density (adjusted HR, 2.19; P = 0.002). Both models stratified outcomes in which pathologic response grading and residual cancer area did not. High-risk configurations were further associated with reduced intratumoral tumor-infiltrating lymphocyte (TIL) density and infiltration ratio, with relative TIL accumulation at the cancer periphery and within the stroma, consistent with an immune-excluded phenotype. Conclusions: Residual cancer–stroma topology quantified from standard H&E slides yields independent prognostic signals after NT in PDAC, provides a cellular immune correlate for spatial risk, and motivates prospective validation and spatially informed adjuvant strategies.

PURPOSE Social determinants of health (SDOH) shape cancer treatment access, adherence, and outcomes, yet their collection and use within National Clinical Trials Network (NCTN) studies remain poorly defined. This study examined how demographic and SDOH-related variables were historically collected and published to identify gaps that constrain the study of social context within NCTN trials. METHODS Participant-level data from completed phase III trials for gastrointestinal (GI) cancers conducted by the Alliance for Clinical Trials in Oncology (Alliance) or its legacy groups from 1999 to 2018 were pooled. Thirteen measures were assessed: four demographic and nine SDOH-related. The proportion of individual participants with data collected for each measure was evaluated. Data utilization was evaluated for all primary articles and via targeted review of related publications using the number either reporting subgroups or publishing analyses for each measure. RESULTS A total of 12,701 participants across 11 trials were included. All trials collected demographic measures (<2% of patients missing), insurance status (1% missing), and ZIP code (3% missing). Education level was collected in two trials (28% missing) with marital and employment status collected in one trial (41% missing for both). No trials collected data on other SDOH-related measures. Education level was the only SDOH-related measure reported in primary articles, and none reported analysis of SDOH-related measures. Of the 149 related publications, <2% reported or analyzed any SDOH-related measure. CONCLUSION Across Alliance and NCTN legacy group phase III trials for GI cancers, demographic variables have been consistently collected and frequently reported or analyzed, whereas SDOH-related measures are inconsistently collected and rarely published in the literature. These findings demonstrate a historical absence of routine SDOH data capture and utilization within NCTN trials.

Abstract Background The multicentre ALaCaRT and ACOSOG Z6051 randomized trials were unable to demonstrate non-inferiority of laparoscopic versus open surgery for rectal cancer with respect to a composite pathology metric indicating successful resection. Neither trial was individually powered to detect differences in long-term recurrence or survival. This planned meta-analysis determined long-term oncological outcomes of laparoscopic versus open proctectomy for rectal adenocarcinoma. Methods This prospective meta-analysis included individual patient data from patients with cT1–3 N0–2 M0 rectal adenocarcinoma enrolled in the ALaCaRT and ACOSOG Z6051 trials. Pathologically successful resection was defined as complete or near-complete total mesorectal excision, a clear circumferential resection margin (CRM; &gt; 1 mm), and a clear distal resection margin (&gt; 1 mm). The non-inferiority margin for disease-free survival (DFS) was an absolute difference of 5% at least 3 years after surgery. Results The combined data set included 935 patients (65.6% men, mean age 60.7 years, mean body mass index 26.7 kg/m2) randomized to open (457 patients) or laparoscopic (478 patients) proctectomy. Pathologically successful resection was lower in the laparoscopic than open group (85.1% versus 89.9%, respectively; pooled estimate 4.6% difference; 95% confidence interval (c.i.) −8.6% to −0.5%). The median follow-up was 60.2 (interquartile range 49.9–61.1) months. Three-year DFS was 75.2% (95% c.i. 71.1% to 79.2%) and 76.5% (95% c.i. 72.5% to 80.6%) for the laparoscopic and open groups, respectively (pooled estimate difference −1.5%; 95% c.i. −7.2% to 4.2%). Non-inferiority of laparoscopic surgery was not demonstrated because the lower one-sided 95% c.i. (−6.3% to 100%) crossed −5%. Three-year locoregional recurrence was higher in laparoscopic than open group (5.4% (95% c.i. 3.3% to 7.5%) versus 2.0% (95% c.i. 0.7% to 3.4%), respectively; pooled estimate 3.1% difference (95% c.i. 0.6% to 5.6%)). A clear CRM was the most significant and only pathological predictor of both DFS (P &lt; 0.0001) and overall survival (P &lt; 0.0001). Conclusion Laparoscopic proctectomy led to a lower rate of pathologically successful resection and a higher rate of locoregional recurrence at 3 years. The possibility of subsequent poorer DFS or overall survival rate requires further evaluation, because this analysis was not specifically powered for these endpoints.

Background: Colorectal neuroendocrine carcinomas (NECs), including small cell (SCNEC) and large cell (LCNEC) subtypes, are rare but aggressive malignancies with limited population-level data. Moreover, prior studies have limited stratification by histologic subtype and anatomic location, despite evidence of disease heterogeneity in colorectal malignancies. This study aimed to characterize the clinical characteristics, treatment patterns, and outcomes of colorectal NEC by histologic subtype and tumor location, and to compare them with neuroendocrine tumors (NETs) and adenocarcinomas (ACs). Methods: A retrospective cohort review was conducted utilizing the SEER database from 2000 to 2022 to identify patients with colorectal SCNEC, LCNEC, NET, and AC. Demographic, clinical, therapeutic and survival data were analyzed and compared using Kaplan–Meier methods, log-rank tests, and Cox proportional hazards regression. Results: A total of 790 SCNEC, 498 LCNEC, 31,200 NET, and 638,898 AC cases were identified. SCNEC and LCNEC were associated with advanced stage at diagnosis (66% and 55% stage IV, respectively) and inferior survival outcomes compared to NET and AC (median OS (mOS) of 7 and 8 months for SCNEC and LCNEC, respectively, p = 0.0002). Stratified by location, colonic SCNEC had the poorest survival (mOS 5 months), worse than rectal SCNEC (mOS 9 months); this pattern was not observed in LCNEC. Surgical resection was associated with improved OS in both NEC subtypes (HR range 0.25–0.56, all p < 0.012). Radiation therapy was associated with improved survival in NEC overall (SCNEC HR 0.58; LCNEC HR 0.71, both p < 0.05), with the observed benefit appearing greatest in rectal NEC. Demographic factors were associated with survival in NET and AC but had no significant impact in NEC. Conclusions: Colorectal SCNEC and LCNEC are highly aggressive malignancies with poor outcomes, with SCNEC demonstrating modestly inferior outcomes compared to LCNEC. This study demonstrates that both histologic subtype and anatomic site of disease are important determinants of prognosis and treatment response. This supports the concept that colorectal NEC represents a biologically heterogeneous disease, with colonic SCNEC showing the worst outcomes and rectal NEC associated with a potential enhanced response to radiation. These findings support the need for further prospective and molecular studies to better define treatment approaches and targeted therapies for these rare malignancies.

Abstract Background The tumor, node, metastasis (TNM) classification at pathological evaluation determines prognosis following cancer treatment. For rectal cancer patients undergoing neoadjuvant therapy, whether ypTNM likely confers different prognosis than pTNM. We compared survival outcomes of patients classified by ypTNM vs pTNM staging. Methods Patients with resected locoregional rectal cancer from the National Cancer Database who underwent upfront surgery (pTNM) and had ≥5 years follow-up (2010-2017) were compared with those receiving neoadjuvant therapy followed by surgery (ypTNM). To address treatment selection bias, analyses were stratified by receipt of guideline-concordant care. Overall survival (OS) was compared using Kaplan-Meier and multivariable Cox regression analyses. Results Of 50 436 patients (median age = 60; 61.4% male), 11 732 (23.3%) underwent upfront surgery and 38 704 (76.7%) received neoadjuvant therapy; 78.8% of the upfront surgery group received guideline-concordant care. In analyses stratified by guideline-concordant care, overall survival was similar for stage 0-I (hazard ratio [HR] = 1.05; 95% CI = 0.96 to 1.15) but significantly worse for ypTNM vs pTNM in stage II (HR = 1.50; 95% CI = 1.27 to 1.77; 5-year OS = 75.6% vs 83.2%) and stage III (HR = 1.60; 95% CI = 1.46 to 1.75; 5-year OS = 67.0% vs 78.2%). Multivariable analysis confirmed ypTNM was associated with worse survival at each stage (stage 0-I: HR = 1.14, P = .004; stage II: HR = 1.49, P &lt; .001; stage III: HR = 1.60, P &lt; .001). Conclusion Stage for stage, ypTNM classification is associated with worse survival than pTNM classification, with increasing difference at higher stages. Future staging systems and management guidelines should account for these differences to optimize prognostication and stratification for clinical trials and surveillance strategies.

e15557 Background: In metastatic colorectal cancer (mCRC), systemic chemotherapy can enable conversion surgery in a subset of patients with initially unresectable disease. Although R0 resection considered a key determinant of long-term survival, its clinical impact across heterogeneous trial populations and treatment strategies remains insufficiently defined. We aimed to clarify the survival benefit of R0 resection after first-line chemotherapy using large-scale individual patient data. Methods: Using the ARCAD database, which comprises 67 randomized clinical trials and approximately 47,000 patients, we conducted a pooled analysis of individual patient data from six first-line randomized clinical trials (COIN, COIN-B, 03-TTD-01, ATOM, SOFT and PARADIGM) for which data on R0 resection were available. Patients with initially unresectable mCRC and available surgical data were categorized into three groups: R0 resection, non-R0 resection, and no surgery. All R0 cases were included, comprising liver-only, lung-only, combined liver and lung metastases, and peritoneal dissemination or other metastatic sites. Overall survival (OS) and progression-free survival (PFS) were evaluated using multivariable Cox proportional hazards models adjusted for age, sex, and performance status. Pre-specified subgroup analyses examined the consistency of outcomes according to tumor response, metastatic site, primary tumor sidedness, RAS status, and targeted therapy class. Results: Among 4,445 eligible patients, 263 underwent R0 , 233 underwent non-R0 resection, and 3,949 received no surgical intervention. The R0 resection group comprised patients with liver-only metastases (n = 176), lung-only metastases (n = 23), and combined liver and lung metastases (n = 27). R0 resection was associated with significantly improved OS and PFS compared with both non-R0 resection and no surgery. These survival benefits were consistently observed across key clinical subgroups, including patients achieving complete or partial response to chemotherapy, those with liver or lung metastases, left- and right-sided primary tumors, and both RAS wild-type and mutant disease. Importantly, the benefit of R0 resection was maintained irrespective of anti-EGFR– or anti-VEGF–based first-line therapy. Conclusions: R0 resection following systemic chemotherapy is strongly associated with durable survival benefits in patients with initially unresectable mCRC across diverse clinical settings. These findings support the pivotal role of conversion strategies and highlight the importance of multidisciplinary evaluation to identify appropriate candidates for curative-intent resection.

3525 Background: Tumor microenvironment (TME) features of colorectal cancer (CRC) may influence detection of circulating tumor DNA (ctDNA) and further refine prognosis. We applied a deep learning histopathologic algorithm to quantify TME features in stage III colon cancers and evaluated their association with postoperative ctDNA status among participants in a phase III FOLFOX-based adjuvant trial (NCCTG N0147). Methods: QuantCRC (Aiforia Technologies) was applied to digitized hematoxylin and eosin-stained whole-slide images of stage III colon adenocarcinomas to extract quantitative histopathologic features. Among cases where data met quality control (N=1817), associations between 15 distinct pathologist-defined features and clinical outcomes—time to recurrence (TTR), disease-free survival (DFS), and overall survival (OS)—were evaluated, stratified by postoperative ctDNA status assessed by a tissue-free assay (Guardant Reveal). Relationships were analyzed using univariate and multivariable Cox proportional hazards models that were adjusted for clinicopathologic and molecular features ( KRAS , BRAF V600E , MMR status). Interaction testing was performed. Results: We found statistically significant quantitative differences for histopathological features by ctDNA status. Features associated with ctDNA positivity(+) included lymphovascular invasion (LVI), and increased %high grade, %tumor budding, %necrosis, and %stroma. ctDNA+ cases had lower %inflammatory stroma and fewer %signet ring cells (all p< 0.006). Multivariable analyses, irrespective of ctDNA status, identified %tumor budding, %mucin, %signet ring cells, %inflammatory tumor bed, and %inflammatory stroma as significantly associated with adverse outcomes (TTR, DFS, OS). Within ctDNA+ cases, higher %immature tumor bed was associated with adverse outcome for all 3 variables. Among ctDNA-negative cases, significantly poorer outcomes (TTR, DFS, OS) were observed for tumors with lower tumor infiltrating lymphocyte (TIL) density and reduced %necrosis. After adjustment, significant interactions with ctDNA status were observed for LVI (p< 0.006) and %signet ring cells (p< 0.035) across all outcome variables, for %necrosis with DFS, OS (p<0.040), and for TILs with TTR (p<0.015). Analysis is ongoing for ctDNA tumor fraction as well as tumor genotyping data (739 genes; Guardant360). Conclusions: QuantCRC identifies TME features associated with postoperative ctDNA status that enable risk-stratification within ctDNA groups. Among ctDNA-negative patients, reduced intratumoral TIL density and reduced tumor necrosis identify high-risk subgroups with inferior clinical outcomes, and may have clinical utility.