Citations

Abstract Background: PDAC is a particularly fatal condition lacking established biomarkers for the choice of first-line treatment (1L). The PurIST algorithm is a gene signature (Rashid et al. Clin. Cancer Res., 2020) that categorizes PDAC tumors into basal or classical molecular subtypes and has been previously validated in a patient cohort of advanced PDAC (N=258). In this post-hoc analysis study, we examine whether the PurIST subtypes can distinguish patients likely to respond to FOLFIRINOX (FFX) versus Gemcitabine + nab-paclitaxel (GnP). Methods: A cohort of de-identified PDAC patients was selected from the Tempus Oncology Database following an IRB-approved protocol. Inclusion criteria required no prior systemic treatment, a surgically unresectable/metastatic status, available RNA-sequencing data from primary or metastatic tissue, and the use of FFX or GnP as 1L systemic therapy with documented outcomes. RNA-sequencing was generated by the CAP/CLIA validated Tempus xR assay. The PurIST gene signature was applied to normalized gene expression values to classify samples into basal or classical subtypes. Univariate and multivariate Cox PH analyzes comparing overall survival (OS) with adjustment for delayed entry, between two common 1L treatment regimens, FFX and GnP, were performed for classical patients with an ECOG performance status of 0 or 1. Results: Application of the PurIST model to the PDAC cohort (N=258) resulted in 67% (N=173) labeled as classical, 23% (N=59) as basal, and the remainder as no-call. Amongst classical patients, 35% (N=61) had a known ECOG score of 0 or 1 and were retained for subsequent analysis. Within this subset, 37 were treated with FFX and 24 with GnP as 1L, with an overall median OS of 11.4 months (95% CI: 9.5-16.5) and a 12-month survival rate of 47.2%. A univariate Cox PH analysis showed that classical patients treated with FFX had a significantly longer OS time (HR (95% CI) = 2.32 (1.29-4.17)). This result remained significant in a multivariate Cox PH, adjusting for age and ECOG, (HR=2.5 (1.15-5.44)). Conclusion: In this real-world cohort of advanced PDAC patients, we showed that classical patients with low ECOG scores had superior OS with 1L FFX treatment compared to 1L GnP. These findings demonstrate the potential for PurIST to aid in optimal treatment selection for patients with advanced PDAC. Citation Format: Stephane Wenric, James M. Davison, John Guittar, Gregory M. Mayhew, Kirk Beebe, Alia Zander, Seung Won Hyun, Kyle Beauchamp, Michael V. Milburn, Vincent Chung, Tanios S. Bekaii-Saab, Charles M. Perou. Real-world validation of the PurIST classifier demonstrates enhanced therapy selection for pancreatic ductal adenocarcinoma (PDAC) patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2542.

Abstract Purpose: There is a need to improve current risk stratification of stage II colorectal cancer to better inform risk of recurrence and guide adjuvant chemotherapy. We sought to examine whether integration of QuantCRC, a digital pathology biomarker utilizing hematoxylin and eosin–stained slides, provides improved risk stratification over current American Society of Clinical Oncology (ASCO) guidelines. Experimental Design: ASCO and QuantCRC-integrated schemes were applied to a cohort of 398 mismatch-repair proficient (MMRP) stage II colorectal cancers from three large academic medical centers. The ASCO stage II scheme was taken from recent guidelines. The QuantCRC-integrated scheme utilized pT3 versus pT4 and a QuantCRC-derived risk classification. Evaluation of recurrence-free survival (RFS) according to these risk schemes was compared using the log-rank test and HR. Results: Integration of QuantCRC provides improved risk stratification compared with the ASCO scheme for stage II MMRP colorectal cancers. The QuantCRC-integrated scheme placed more stage II tumors in the low-risk group compared with the ASCO scheme (62.5% vs. 42.2%) without compromising excellent 3-year RFS. The QuantCRC-integrated scheme provided larger HR for both intermediate-risk (2.27; 95% CI, 1.32–3.91; P = 0.003) and high-risk (3.27; 95% CI, 1.42–7.55; P = 0.006) groups compared with ASCO intermediate-risk (1.58; 95% CI, 0.87–2.87; P = 0.1) and high-risk (2.24; 95% CI, 1.09–4.62; P = 0.03) groups. The QuantCRC-integrated risk groups remained prognostic in the subgroup of patients that did not receive any adjuvant chemotherapy. Conclusions: Incorporation of QuantCRC into risk stratification provides a powerful predictor of RFS that has potential to guide subsequent treatment and surveillance for stage II MMRP colorectal cancers.

TPS578 Background: Liver transplantation is a curative treatment option in hepatocellular carcinoma (HCC) however; up to 20% of patients develop recurrent disease. HCC recurrence post-transplant is usually extrahepatic (up to 67%) hence requires effective systemic therapy options. Available data are limited and restricted to small non-randomized studies and case series. Lack of prospective clinical trial data and limited data indicates an area of unmet need in treatment of recurrent HCC after liver transplantation. This phase II study aims evaluate the safety and efficacy of lenvatinib in patients with recurrent HCC after liver transplantation. Methods: This is a multi-institutional phase II trial with lenvatinib in patients with recurrent HCC after transplantation. Lenvatinib is administered 12 mg daily orally in patients ≥60 kg, and 8 mg daily orally in patients <60 kg. Each cycle is 28 days. Restaging scans will be performed every 8 weeks. Eligible patients must have histologically proven HCC that has recurred after liver transplantation and not amenable for surgical resection, age ≥18 years, ECOG PS 0-1, Child Pugh Class A, measurable disease per RECIST version 1.1, adequate organ function, no prior systemic therapy with lenvatinib or another systemic therapy in the post-transplant setting. Prior liver directed therapy is allowed, should be at least >28 days prior to the study enrollment, and should have at least one measurable untreated lesion by RECIST 1.1 Primary endpoint is overall response rate (ORR). Secondary endpoints are safety/tolerability, progression free survival, and overall survival. Pre-treatment and on-treatment peripheral blood samples will be collected for correlative research. A Simon`s two stage Minimax design is employed (H0: ORR = 5%; H1: ORR = 24%; Type I error = 0.05; power = 80%). In the first stage, 11 patients will be accrued, and if there is no objective response among them, the study will be stopped for futility. Otherwise, additional 6 patients will be accrued for a total of 17 patients. This study is currently enrolling patients. Clinical trial information: NCT05103904 .

688 Background: PACC is a rare malignancy originating from the exocrine pancreas, accounting for less than 1% of all pancreatic cancers. Due to the rarity of the disease entity, there is a paucity of data to guide treatment decisions. This retrospective study aims to provide additional clinical characteristics and outcomes to aid in future treatment decisions. Methods: Pathology records from Mayo Clinic (AZ, FL, MN) patients (pts) denoting acinar or mixed-acinar cell carcinoma were searched between 2002 to 2023 and selected for retrospective review. Pt demographics, treatment courses, and next generation sequencing (NGS) were collected. Results: A total of 62 pts (74% male, n = 46) were identified with median age 64 years old. Histologic subtypes were 67% pure acinar cell carcinoma (42/62), 24% mixed acinar-neuroendocrine (15/62), and 8% mixed acinar-adenocarcinoma (5/62). AJCC stages at diagnosis were 34% stage I/II (21/62), 16% stage III (10/62), and 50% stage IV (31/62). Early-stage disease was treated with upfront surgical resection (81%, 17/21). Locally advanced disease received neoadjuvant therapy (NAT) followed by surgical resection (80%, 8/10). FOLFIRINOX was most often chosen as NAT (65%, 11/17), while others received gemcitabine-based NAT. The R0 resection rate was 86%. The 3 and 5-year survival estimates for stage III were 90.9% (95% CI: 75.4 – 100%) and 67.3% (95% CI: 42.3 – 100%), respectively. The 3 and 5-year survival estimates for stage IV were 36.6% (95% CI: 18.6 – 71.9%) and 29.3% (95% CI: 13.1 – 65.5%), respectively. Median survival time for stage IV was 3 years. Somatic NGS testing was done in 24 pts with alterations found in: homologous recombination (HR) in 42% (10/24); RAF alterations in 25% (6/24); mismatch repair (MMR) in 13% (3/24; none of them with MMR germline mutations), 1 ETV6-NTRK3 fusion, and 1 FGFR mutation. Germline NGS testing was done in 21 pts and alterations in HR were seen in 33% (7/21) of pts. This led to additional therapeutic options in 46% (11/24) of pts. Conclusions: Unlike PDAC, PACC is a genomically diverse disease, with potentially targetable alterations in RAF, HRD, and MMR genes, offering additional therapeutic options for significant number of pts. In addition, more than one-third of the pts harbored germline mutations in HR genes. Therefore, somatic and germline testing should be considered for any pt diagnosed with PACC.

687 Background: The NAPOLI 3 study (NCT04083235, N = 770) reported that NALIRIFOX improved overall survival (OS) vs Gem+NabP with manageable toxicity in 1L treatment of metastatic pancreatic adenocarcinoma. We explored changes in CA19-9 levels and their potential associations with efficacy as an important tumor marker in pancreatic adenocarcinoma. Methods: In NAPOLI 3, CA19-9 was evaluated at baseline and every 8 weeks until patients discontinued study treatment. The detection limit of CA19-9 was 8000 kU/L in this study. The Cox proportional hazards regression and logistic regression were employed to investigate the relationship between CA19-9 decrease and OS, progression-free survival (PFS), and overall response rate (ORR). Results: Patients with evaluable CA19-9 (levels =< 8000) at baseline and additional measurements at weeks 8 and 16 were included in the analysis (NALIRIFOX, n = 179; Gem+NabP, n = 194). The median baseline CA19-9 level was 378.0 and 409.7 kU/L for the NALIRIFOX and Gem+NabP arms, respectively. Overall, patients with (vs without) any CA 19-9 decrease by week 16 had a higher ORR (59.9% vs 35.2%; p = 0.002), a longer median PFS (9.2 vs 6.2 months; p < 0.001) and a longer median OS (14.2 vs 8.7 months; p = 0.005), respectively in a pooled analysis of the treatments. In the NALIRIFOX arm, patients with any CA19-9 decrease by week 16 had a higher confirmed ORR of 65.1% compared with those without at 42.4% ( p < 0.001), a median PFS of 9.5 vs 7.1 months ( p < 0.001) and a median OS of 15.4 versus 8.4 months ( p = 0.004), respectively. In the Gem+NabP arm, patients with CA19-9 decrease by week 16 had a higher ORR of 55.5% compared with those without at 23.8% ( p = 0.012), a median PFS of 7.6 versus 5.8 months ( p < 0.001) and a median OS of 13.7 versus 11.9 months ( p = 0.235), respectively. Conclusions: CA19-9 decrease by week 16 has the potential to be an early prognostic factor for OS, PFS and ORR. The results should be interpreted with caution as a considerable percentage of patients were excluded due to non-evaluable CA19-9 that exceeded the lab detection limit of 8000 kU/L. Clinical trial information: NCT04083235 .

538 Background: In biliary tract cancer (BTC), TP53 is the most commonly altered gene and may co-occur with KRAS alteration. The presence of a co-alterations in of TP53 and KRAS is associated with poor prognosis in many cancers. In patients (pts) with advanced BTC, the prognostic implications of such co-alterations have not been fully investigated. Methods: This is a pooled analysis of SCRUM-Japan GOZILA and MONSTAR-SCREEN-1 and -2 studies. Genomic profiling was conducted with Guardant360 for plasma in GOZILA, FoundationOne CDx for tissue and FoundationOne Liquid CDx for plasma in MONSTAR-SCREEN-1, and CARIS MI Profile for tissue in MONSTAR-SCREEN-2. Pts with advanced BTC receiving systemic therapy were included in this study. Results: Among 636 pts with advanced BTC, 85 had TP53/KRAS co-alteration, 293 had TP53, 44 had KRAS, and 214 had neither KRAS nor TP53 alteration (WT/WT). Tumors with TP53 alteration had significantly higher level of tumor mutation burden (TMB) compared to the other groups (3.8 mut/Mb for TP53/KRAS, 5.0 mut/Mb for TP53, 2.8 mut/Mb for KRAS, and 2.5 mut/Mb for WT/WT, respectively, P<0.001). In addition, the frequency of microsatellite instability-high (MSI-High) in the TP53/KRAS group (11.0%) was significantly higher compared to the TP53 group (3.1%, P<0.05), and the WT/WT group (0.6%, P<0.001), respectively. The objective response rate of first-line therapy in the TP53/KRAS group (8.2%) was significantly lower than in the other groups (20.8% for TP53, 23.3% for KRAS, and 19.7% for WT/WT groups, P=0.035). There was no pts treated with durvalumab plus gemcitabine and cisplatin. Two pts with TP53/KRAS alteration and MSI-High received pembrolizumab monotherapy, and partial response was achieved with a progression-free survival of 9.4 and 22.0 months. The median overall survival (OS) for pts treated with first-line therapy of the TP53/KRAS, KRAS, TP53, and WT/WT groups were 13.6 (95% confidence interval [CI], 11.5-15.5), 14.3 (95%CI, 9.7-25.9), 18.8 (95%CI, 16.9-20.6), and 22.7 months (95%CI, 20.4-25.9), respectively. Multivariate analysis identified TP53/KRAS alteration (hazard ratio [HR] 2.14, 95%CI 1.43-3.22, P<0.001), number of detected variants (≥2) (HR 1.50, 95%CI 1.04-2.16, P=0.029), locally advanced (HR 1.72, 95%CI 1.05-2.83, P=0.033), and metastatic status (HR 1.78, 95%CI 1.39-2.28, P<0.001) as independent prognostic factors for shorter OS. Conclusions: Patients with advanced BTC with co-occurring TP53/KRAS alterations have worse prognosis. Interestingly, the presence of these co-alterations was associated with a higher likelihood of MSI-High phenotype.

283 Background: The randomized phase II CALGB 80803 trial evaluated use of PET imaging for early assessment of induction chemotherapy (iCT) responsiveness to tailor therapy for patients with esophageal and gastroesophageal junction adenocarcinomas (EC) undergoing trimodality therapy. The primary endpoint of improving pathologic complete response rates using PET-adapted therapy was met. A companion QOL study aimed to characterize patients’ experience through iCT, chemoradiation (CRT) and surgery (S). Methods: Between 11/2011 and 5/2015, 241 eligible patients were randomized to an iCT regimen: modified oxaliplatin, leucovorin, and 5-fluorouracil (FOLFOX) or carboplatin/paclitaxel (CP), followed by PET scan then CRT, either continuing on the same CT for PET-responders (PET-R) or crossing over to the alternative CT for PET-nonresponders (PET-NR). We prospectively collected QOL domains and symptoms at baseline (T1), after iCT (T2), after CRT (T3), and 3- (T4) and 6- months (T5) after S using the EORTC QLQ-C30, The Esophageal Cancer subscale (EORTC OES18), FACT Neurotoxicity Scale (FACT-NTX), and 6 questions from the PRO-CTCAE. QOL scores were compared between iCT groups and between PET-R and PET-NR at each time point using mixed models. The association of QOL scores at enrollment with overall survival (OS) was tested using Cox regression. Results: 189 patients enrolled on the QOL sub-study, 92 received induction FOLFOX and 97 induction CP. Of those, 110 were PET-R and 79 were PET-NR. 97.9% went on to CRT, and 83.6% underwent S. Global QOL and symptoms statistically significantly worsened from T1 to T2 in 14 of 25 domains, and remained significantly worsened from T1 at: T3 for 19 of 25 domains, T4 for 17 of 25 domains, and T5 for 6 of 25 domains. Changes from T1 significantly favored iFOLFOX (vs iCP) for ability to eat (at T3 and T4), GI symptoms (at T3 and T4), and talking (at T5). Changes from T1 significantly favored iCP (vs iFOLFOX) for neuropathy (at T2, T3, and T4) and coughing (at T5). Proportion of patients reporting worsened PRO-CTCAE scores did not differ between PET-R or PET-NR groups . Multiple QOL domains and symptoms were associated with OS including role functioning, global health status/QOL, appetite loss, pain, dysphagia, and ability to eat (all p<0.002). Conclusions: QOL was impacted most by CRT but returned to baseline 6 months after surgery for most domains. Observed symptom differences did not consistently favor one iCT regimen. Early interventions such as nutritional support and prehabilitation should be studied to improve QOL and OS. Clinical trial information: NCT01333033 .

200 Background: We developed and validated a quantitative segmentation algorithm (QuantCRC) to predict disease recurrence in stage I-III colorectal cancer patients (pts) based on the analysis of digitized hematoxylin and eosin (H+E) stained pathology slides. In this study, we aim to determine if QuantCRC analysis on pre-treated RC biopsies can predict pathological complete response (pCR) after NAT which include total neoadjuvant therapy (TNT), chemoradiation (CRT) and others. Methods: Stage II-IV RC pts treated with curative intent modalities between 2005-2023 at Mayo Clinic and University of Pittsburgh were evaluated. Eligible pts had pre and post-treatment tissue available for analysis. Clinical characteristics, treatment, and outcome data were extracted from the medical record. QuantCRC extracted 15 features: %tumor, %stroma, tumor:stroma ratio, %TB/PDC, %mucin, %necrosis, %high-grade, %signet ring cells, tumor-infiltrating lymphocytes (TILs) per cm2 of a tumor, %immature stroma (tumor bed), %inflammatory stroma (tumor bed), %mature stroma (tumor bed), %immature (stromal region), %inflammatory (stromal region), and %mature (stromal region). The associations between the QuantCRC features and pCR were evaluated using Wilcoxon rank-sum tests and logistic regression models while adjusting for primary tumor location and NAT. Results: The identified 288 pts had the following demographics: median age 60, 59% male, 52% distal tumor, 42% TNT. Pts who achieved pCR had smaller pre-treatment tumors (p=0.03), higher TILS, and lower %immature (stroma) (Table 1). After multivariable adjustment, higher TILS and lower %immature (stroma) remain to be significantly associated with a higher likelihood of pCR. A higher %mature (stroma) and %mature stroma (tumor bed) were also identified, in multivariable models, to be associated with a higher rate of pCR. NAT protocol and tumor location (proximal vs. distal) were not associated with pCR. Conclusions: The ability to integrate pathological features with AI may allow for personalized treatment. Using this technology, we recognize that patients who harbor a more mature stromal archetype and inflammatory tumor predisposition, are more likely to achieve pCR to conventional NAT. These pathological features are not currently incorporated into risk stratification in RC. Additional validation and integration into current risk stratification methods is warranted. [Table: see text]

175 Background: Alterations to mismatch repair (MMR) genes such as MLH1, MSH2, MSH6, and PMS2, can lead to microsatellite instability-high (MSI-H) tumors. MMR mutations can be inherited in Lynch syndrome (LS) but can also be a result of de novo alterations resulting in MSI-H malignancies. Treatment with immune checkpoint inhibitors (ICIs) have been shown to improve survival in such patients (pts) compared to systemic chemotherapy. However, there is a paucity of information in the literature with respect to outcomes of pts with germline vs somatic MMR mutations in MSI-H colorectal cancer (CRC). Furthermore, the presence of underlying BRAF mutation confers resistance to chemotherapy in pts with CRC, however data regarding outcomes with immunotherapy in such pts with MSI-H CRC is lacking. Methods: Pt records from the Mayo Clinic (AZ, MN, FL) between 2008-2023 denoted as MSI-H CRC, were included for retrospective review. Pt demographics, treatment courses, and genomic profiles were collected. Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method. Outcome differences between sub-groups were accessed with the log rank test and univariate analyses were assessed with Cox-regression. Results: A total of 81 pt records were identified (n = 18 LS, n = 63 non-LS). Stage IV disease was found in 28% of LS pts vs 59% of non-LS pts at diagnosis. Pembrolizumab was the most common ICI selected for metastatic CRC pts for both LS and non-LS pts (65% vs 94%) with median treatment duration for each group 11.7 vs 8.8 months. There were no differences in OS or PFS for any stage between LS vs non-LS. Median OS for all patients was 82 months. For all stage IV patients, median OS was 44 months, and median PFS was 19 months. Interestingly, for stage IV pts treated with immunotherapy, tumors that harbored BRAF V600E mutation (n = 21) vs BRAF wild type (n = 20) had a significantly lower median OS 19 vs 113 months (HR = 2.69, p = 0.043) as well as median PFS 12 vs 95 months (HR = 2.48, p = 0.041). Conclusions: In this study, we found that patient treated with ICIs have similar outcomes in the presence of germline vs. somatic MMR mutations in MSI-H CRC. The presence of an associated BRAF V600E mutation, which occurs in non-LS MSI-H CRC conferred worse outcomes.