Citations

559 Background: Cabozantinib, a multikanase inhibitor, is approved by the Food and Drug Administration (FDA) for treatment of advanced stage hepatocellular carcinoma (HCC) following progression on sorafenib. The CELESTIAL study which demonstrated benefit from cabozantinib following sorafenib included only patients with Child Pugh class A liver function. Recently, bevacizumab plus atezolizumab has replaced sorafenib as the first line treatment for HCC. It is unclear whether there is benefit from using Cabozantinib following progression on immunotherapy as CELESTIAL trial included very few patients who received prior immunotherapy. We describe the outcomes of individuals with advanced stage HCC treated with Cabozantinib following progression on immunotherapy. Methods: This was a multicenter, retrospective analysis of patients with advanced HCC diagnosed between 2010-2021 at Mayo Clinic Arizona, Florida, and Minnesota. Progression free survival (PFS) and median overall survival analysis were performed using Kaplan-Meier method. Results: We identified a total of 26 patients with advanced stage HCC who received cabozantinib following progression on immunotherapy. The median age of patients was 61 years (range, 39 – 81) and the majority were male (85%). Eighteen (72%) patients had Child Pugh A at initiation of cabozantinib therapy. Four (15%) patients received cabozantinib as second line therapy, the rest received it as third line or later. PFS on cabozantinib was 2.1 months (95% CI: 1.3 – 3.9) and median overall survival from time of cabozantinib initiation was 7.7 months (95% CI: 5.3 – 14.9). PFS was shorter with Child Pugh Class B, 1.3 months (95% CI: 0.9 – NE) compared to those with Child Pugh Class A, 2.1 months (95% CI: 1.5 – 4); although this difference was not significant (p=0.55). Common adverse events included fatigue (50%), anorexia (35%), aspartate aminotransferase (AST) elevation (35%), and diarrhea (31%); 7 (26%) patients experienced Grade 3 or greater adverse events including hypertension, diarrhea, anorexia, and bowel obstruction. Two patients discontinued cabozantinib due to side effects including one for uncontrolled blood pressure elevations and the other due to fatigue. Conclusions: The optimal sequencing of therapy for patients with advanced HCC following progression on immunotherapy is unknown. Treatment with cabozantinib may improve clinical outcomes following progression on immunotherapy with similar adverse event profile. This study included patients with Child Pugh class B liver disease (28%) and heavily pretreated population and demonstrated mPFS and mOS similar to other work examining outcomes of cabozantinib in real world setting after progression on sorafenib. Further studies to determine optimal treatment sequencing for this patient population are needed.

507 Background: Lenvatinib, a multikinase inhibitor, is an FDA approved treatment for advanced hepatocellular carcinoma (HCC) in the first line setting. Atezolizumab and bevacizumab are considered new standard of care as first line therapy after results of the IMBrave 150 trial. Currently, we do not have data to suggest any second-line treatment after administration of immunotherapy. We describe the clinical outcomes in patients with advanced HCC who received lenvatinib following treatment with immunotherapy. Methods: We conducted a multicentric, retrospective analysis of patients with advanced HCC diagnosed between 2010 and 2021 at Mayo Clinic in Minnesota, Arizona, and Florida. The study was reviewed and approved by the intuitional review board. The primary outcomes were overall survival (OS) and progression free survival (PFS). Results: We identified 53 patients with advanced HCC who received lenvatinib following immunotherapy. Most patients (83%) were male. Median age at start of lenvatinib was 67 years old. Forty-two (79%) patients had a Child-Pugh score of A at diagnosis while 30 (58%) patients were still Child-Pugh A at time of lenvatinib initiation. Risk factors for HCC included Hep C (43%), alcohol use (34%), NASH (15%) and hepatitis B (7%). Forty-five (85%) patients received lenvatinib in the 2nd line and 8 (15%) patients received it as third line or later. At time of data extraction, 38 (72%) patients had died. Median PFS was 4 months (95% CI: 3 – 6) and median OS from time of lenvatinib initiation was 13 months (95% CI: 6 – 24). The most common adverse events of any grade included fatigue (53%), hypertension (37%), AST elevation (30%), anorexia (28%), bilirubin elevation (25%) and diarrhea (25%). Twenty-one (40%) patients experienced grade 3 or higher adverse events including hypertension (25%), confusion (6%), acute kidney injury (2%), hyperkalemia (2%), ALT elevation (2%), proteinuria (2%), arthralgia (2%), heart failure (2%), AST elevation (2%), bilirubin elevation (2%), palmar-plantar erythrodysesthesia (2%), oral mucositis (2%), weight loss (2%), hypothyroidism (2%), anorexia (2%), fatigue (2%) and diarrhea (2%). Seven patients stopped treatment due to adverse events: 1 for hypertension, 2 for confusion, 1 for heart failure, 2 for fatigue, and 1 for elevated bilirubin. Conclusions: The optimal sequencing of therapy for patients with advanced HCC following progression on immunotherapy remains unknown. We found that median OS was 13 months in patients who received lenvatinib after immunotherapy which is comparable to survival in other studies when used as first line therapy. Our experience demonstrates that patients may benefit from treatment with lenvatinib following initial progression on immunotherapy.

225 Background: HR deficient (HRD) CRC has improved outcomes following exposure to DNA damaging agent (DDA) (irinotecan, IR; oxaliplatin, OX) compared to HRP CRC. Low expression of wild type (WT) BRCA1 mRNA is associated with prolonged OS in ovarian cancer; however, this finding has not been investigated in CRC or outside of BRCA. Here, we examine the effect of low expression of HR genes in HRP CRC on post-DDA survival. Methods: 12,860 CRC samples were analyzed by NGS (592, NextSeq; WES, NovaSeq) and WTS (NovaSeq) at Caris Life Sciences (Phoenix, AZ). Samples were classified by RNA expression percentiles. Real world OS was extracted from insurance claims and calculated using Kaplan-Meier estimates for molecularly defined cohorts from first of OX or IR to last contact. Results: Post-IR survival was prolonged with low expression of ATM, CHEK2 and PALB2 in WT ATM, PALB2, and CHEK2 WT CRC, respectively (bottom vs. top 10%, bottom vs. top 25%; p<0.05). Notably, low PALB2 expression (bottom 10%) showed a 14.5-month post-IR benefit compared to high PALB2 expression (top 10%) in WT PALB2 CRC (p=0.003). Post-OX survival was not significantly prolonged with low expression of CHEK2 in WT CHEK2 CRC (bottom 10% vs top 10%, bottom 25% vs top 25%) but was with low expression of ATM (+9.7 months, p=0.02) and PALB2 (+5.6 months, p=0.03) in WT ATM and PALB2 CRC, respectively (all bottom 25% vs top 25%). Conclusions: Here we report the first findings to suggest a novel subclass of CRC defined as the low expression of mRNA of non-mutated HRD genes that exhibit sensitivity to DDA. Low expression of WT ATM, CHEK2, and PALB2 correlates with prolonged OS following IR, post-OX survival was prolonged with low expression of ATM and PALB2. Further characterization defining sensitivity of low expressing HRP genes to DDA may help guide treatment considerations in HRP CRC. [Table: see text]

199 Background: The progression of neoplasia in colorectal cancer (CRC) has been well characterized, with the evolution typically involving mutations in APC, KRAS, and p53, among others. POLE/POLD1 genes encode for proteins essential in enzymatic DNA polymerase function, yet POLE/POLD1 mutations in tumors are poorly characterized. Pathogenic mutations in POLE/POLD1 lead to decreased fidelity of DNA replication, resulting in a high tumor mutational burden (TMB-H) independent of deficient mismatch repair (dMMR) and high microsatellite instability (MSI-H). Studies have shown associations between this hypermutated phenotype and susceptibility to immune checkpoint inhibition, which may be attributable to neoantigen creation. As such, these tumors are a clinically relevant phenotype requiring further investigation. Here, we characterized POLE/POLD1 alterations in a large, real-world cohort of patients with CRC. Methods: We retrospectively analyzed de-identified records of 9,136 primary CRC patients profiled with the Tempus xT assay. The assay includes DNA-seq of 595-648 genes at 500x to evaluate single-nucleotide variants, insertions/deletions, and copy number changes. Immunological markers analyzed included tumor mutational burden (TMB), MSI, and dMMR. MSI-H was determined by the assay through assessment of 239 loci. dMMR was determined by immunohistochemistry. Results: A total of 217 patient tumors harbored somatic POLE/POLD1 mutations (n = 203 POLE, n = 13 POLD1, and n = 1 POLE and POLD1; none germline), with no differences noted in baseline demographics including gender and age. Among the POLE/POLD1-mutant cohort, POLE copy number losses accounted for most mutations (n = 127, 59%), with short variants and copy number amplifications accounting for 35% (n = 76). The remainder of tumors exhibited POLD1 copy number changes (n = 14), including one with both POLE and POLD1 copy number loss. POLE/POLD1-mutated tumors presented with a lower frequency of MSI-H compared to wild-type (1.8% vs 6.1%, P= 0.018). Conversely, there was a higher frequency of TMB-high cases ( > 10 mut/Mb) for POLE/POLD1-mutated compared to wild-type tumors (22% vs 9.9%, P< 0.001). Differences between POLE/POLD1-mutated and wild-type tumors were also observed among many co-mutated genes, including APC (80% vs 65%, P< 0.001), ALK (31% vs 11%, P< 0.001), ATM (12% vs 3.6%, P< 0.001), BRCA2 (12% vs. 3.2%), and RET (24% vs 8.9%, P< 0.001). Conclusions: Patients with POLE/POLD1 mutations exhibited significant differences across immunological markers and molecular co-alterations. POLE/POLD1 mutations in CRC have been previously described to present with a hypermutated phenotype; however, 78% of tumors exhibited low TMB despite POLE/POLD1 mutations. Thus, these results have identified POLE/POLD1-mutated tumors as a unique genomic subpopulation, and further studies are needed to better characterize POLE/POLD1 mutations in CRC.

198 Background: HER2 overexpression/amplification (HER2+) occurs in 3%-5% of patients (pts) w/ metastatic colorectal cancer (mCRC). Rates of HER2+ can increase to ~10% in pts w/ RAS/BRAF wild-type mCRC tumors. The MOUNTAINEER trial (NCT03043313) evaluated the efficacy and safety of the investigational combination of tucatinib with trastuzumab in pts with HER2+ and RAS wild-type mCRC. Established regional guidelines for mCRC recommend HER2 testing and HER2-directed treatment options; however, there is currently no established best practice for HER2 testing and interpretation in mCRC. Here, we present data from a concordance analysis comparing breast and gastric HER2 testing algorithms in the mCRC setting. Methods: The MOUNTAINEER trial enrolled pts w/ HER2+ mCRC identified using ≥1 method: tissue-based local immunohistochemistry (IHC), in situ hybridization (ISH), and/or next-generation sequencing (NGS) testing. Archival or fresh tumor tissue was submitted to a sponsor-designated central laboratory for confirmatory HER2 testing w/ IHC/FISH per the package insert of the FDA approved assay and scored by both the breast and gastric algorithms for HER2 IHC. A positive result per the breast scoring criteria for IHC requires circumferential membrane staining for HER2, while the gastric criteria allows for circumferential, basolateral, or lateral staining patterns. Results: A total of 114 pts were enrolled with HER2+ tumors per ≥1 local testing methods; 69 pts were HER2+ by NGS, 46 by IHC 3+, and 36 by ISH. Of 105 pts who had tissue available for central HER2 testing w/IHC/FISH, 98 had valid HER2 results; 82/98 (83.7%) of pts had tumors centrally confirmed as HER2+ using both the breast and gastric algorithms. Tissue samples from pts in the MOUNTAINEER trial had 100% concordance between breast and gastric algorithms in HER2 status and 99% concordance in HER2 IHC score. Conclusions: Central pathology testing using both the breast and gastric criteria showed high concordance between these two commonly used algorithms. A high central confirmation rate of local HER2+ results was also observed. These data support the use of either the breast or gastric algorithms to identify HER2+ mCRC tumors until an FDA-approved HER2 assay is available for mCRC. Clinical trial information: NCT03043313 . [Table: see text]

139 Background: The fibroblast growth factor receptor (FGFR) pathway plays a key role in cellular proliferation, migration, survival and angiogenesis. Aberrant signaling through FGFR in colorectal cancer and other malignancies results from gene amplification or mutation, chromosomal translocation or ligand-dependent activation of the receptors. Pemigatinib is an oral inhibitor of FGFR1-3 with proven efficacy in FGFR-altered cholangiocarcinoma and myeloid/lymphoid neoplasms, among others. We hypothesized that pemigatinib would improve response rates compared to historical controls in patients with refractory FGF/FGFR-altered mCRC. Methods: ACCRU-GI-1701 was a multicenter, single-arm, Simon’s two-stage phase II clinical trial (NCT04096417) of the FGFR inhibitor pemigatinib in patients (pts) with FGF/FGFR-altered mCRC. Eligible pts had received prior fluoropyrimidine, oxaliplatin, irinotecan, and anti-VEGF/anti-EGFR/anti-PD-1 if eligible. Pts received pemigatinib 13.5 mg once daily on d1-21 of each cycle, with option to escalate to 18 mg in c2 if well tolerated. The primary endpoint was (unconfirmed) objective response (OR). A sample size of 21 evaluable pts would provide 82% power to detect a true OR rate of 20% or greater compared to a historical control of 5 % with a one-sided type I error rate of 0.1. A prespecified interim analysis for futility was planned after 12 evaluable patients. Results: A total of 14 patients were enrolled in the first stage of the study, and all were evaluable for the primary endpoint. No OR were observed (out of 12) crossing the futility boundary and resulting in permanent closure of the study. Among all enrolled patients, median age was 60.5 years, 71.4% were male, 92.9% Caucasian, 42.9% with no prior exposure to TAS-102 or regorafenib, and 64.3% with left-sided primary tumors. Treated patients all had tumors with FGFR1-4 mutations and/or FGF/FGFR amplifications by tissue- and/or blood-based molecular testing; no FGFR translocations were present. OR rate for this study was 0% (95% CI, 0-23.2%), with one patient achieving stable disease as best response. Median progression-free survival was 9.1 weeks (95% CI, 7.9-not evaluable [NE]), and median overall survival was 7.9 months (95% CI, 3.4-NE). Grade 3+ adverse events (AE) were seen in 42.9% of treated patients (including 1 grade 5 AE). Most commonly occurring AEs of any grade were anemia, hyperphosphatemia, alkaline phosphatase increased, aspartate aminotransferase increase, and fatigue. Conclusions: Pemigatinib demonstrated evidence of safety but not clinical activity in this population of patients with FGF/FGFR-altered mCRC. It is unknown whether pemigatinib would be active in mCRC patients with FGFR translocations/fusions as these were not represented in our trial. Translational studies are planned to investigate mechanisms of resistance to this therapy. Clinical trial information: NCT04096417 .

PURPOSE This randomized, open-label trial compared the efficacy and safety of adjuvant nab-paclitaxel + gemcitabine with those of gemcitabine for resected pancreatic ductal adenocarcinoma (ClinicalTrials.gov identifier: NCT01964430 ). METHODS We assigned 866 treatment-naive patients with pancreatic ductal adenocarcinoma to nab-paclitaxel (125 mg/m 2 ) + gemcitabine (1,000 mg/m 2 ) or gemcitabine alone to one 30-40 infusion on days 1, 8, and 15 of six 28-day cycles. The primary end point was independently assessed disease-free survival (DFS). Additional end points included investigator-assessed DFS, overall survival (OS), and safety. RESULTS Two hundred eighty-seven of 432 patients and 310 of 434 patients completed nab-paclitaxel + gemcitabine and gemcitabine treatment, respectively. At primary data cutoff (December 31, 2018; median follow-up, 38.5 [interquartile range [IQR], 33.8-43 months), the median independently assessed DFS was 19.4 ( nab-paclitaxel + gemcitabine) versus 18.8 months (gemcitabine; hazard ratio [HR], 0.88; 95% CI, 0.729 to 1.063; P = .18). The median investigator-assessed DFS was 16.6 (IQR, 8.4-47.0) and 13.7 (IQR, 8.3-44.1) months, respectively (HR, 0.82; 95% CI, 0.694 to 0.965; P = .02). The median OS (427 events; 68% mature) was 40.5 (IQR, 20.7 to not reached) and 36.2 (IQR, 17.7-53.3) months, respectively (HR, 0.82; 95% CI, 0.680 to 0.996; P = .045). At a 16-month follow-up (cutoff, April 3, 2020; median follow-up, 51.4 months [IQR, 47.0-57.0]), the median OS (511 events; 81% mature) was 41.8 ( nab-paclitaxel + gemcitabine) versus 37.7 months (gemcitabine; HR, 0.82; 95% CI, 0.687 to 0.973; P = .0232). At the 5-year follow-up (cutoff, April 9, 2021; median follow-up, 63.2 months [IQR, 60.1-68.7]), the median OS (555 events; 88% mature) was 41.8 versus 37.7 months, respectively (HR, 0.80; 95% CI, 0.678 to 0.947; P = .0091). Eighty-six percent ( nab-paclitaxel + gemcitabine) and 68% (gemcitabine) of patients experienced grade ≥ 3 treatment-emergent adverse events. Two patients per study arm died of treatment-emergent adverse events. CONCLUSION The primary end point (independently assessed DFS) was not met despite favorable OS seen with nab-paclitaxel + gemcitabine.

Abstract Background: PDAC is a highly morbid disease with no validated biomarkers for first-line (1L) treatment selection. The PurIST single-sample molecular subtyping gene signature, initially described by Rashid et al. (Clin. Cancer Res., 2020), classifies PDAC tumors as basal or classical. Prior work showed that these subtypes are associated with prognosis and that basal subtype patients have significantly lower objective response rate to FOLFIRINOX (FFX) compared to classical subtype patients. This suggests potential implications for treatment with FFX versus gemcitabine and nab-paclitaxel (GnP). Here, we retrospectively demonstrate the clinical validity of PurIST implemented as a laboratory developed test (LDT) on the Tempus Labs sequencing platform using a real-world dataset of advanced PDAC patients. Methods: De-identified PDAC patients were selected from the Tempus Oncology Data Ecosystem under an IRB-approved protocol according to the following inclusion criteria: no systemic treatment, surgically unresectable/metastatic, available RNA-sequencing data from primary or metastatic tissue, and FFX or GnP as 1L systemic therapy with available outcomes. Sequencing was performed by the CAP/CLIA validated Tempus xT assay. The PurIST model was applied to normalized RNA-sequence abundance files to compute a basal or classical subtype label. Predefined statistical analysis parameters included 12-month survival rate and median overall survival (OS) in FFX treated patients. OS was compared using Kaplan-Meier estimates, hazard ratios, and log-rank statistical tests. Results: 258 PDAC patients (64.9 +/- 9.9 yrs, 42% female), were identified for analysis with median OS of 11.7 months (95% CI: 10.6-13.7) and 12-month censorship rate of 12.8%. 151 patients were treated with FFX and 107 with GnP. 42 patients (28%) receiving FFX and 31 patients (29%) receiving GnP were classified as basal. Among FFX treated patients, median OS was 14.4 months (95% CI: 12.5-16.9) in classical patients vs. 9.4 months (95% CI: 8.3-14.5) in basal patients (HR = 1.72, 95% CI = 1.2-2.6, p=0.006). The 12-month survival rate was significantly lower in basal patients receiving FFX vs. classical patients (33.3% vs. 59.4%, p=0.011). In basal patients, no difference in OS was observed between FFX and GnP groups (p=0.6). Classical patients receiving FFX had a 14.4 months median OS vs. 10.8 months for patients receiving GnP (p=0.046). Conclusions: In this real-world cohort, we validate the association between PurIST subtypes and PDAC patient survival when administered FFX or GnP. Among FFX-treated patients, classical patients had significantly better outcomes compared to basal patients. Moreover, classical patients appeared to have improved outcomes with FFX vs. GnP. These findings represent underlying biological PDAC differences and demonstrate the clinical validity of PurIST as a prognostic marker in PDAC patients when performed as an LDT on the Tempus xT platform. Ongoing evaluation of PurIST performance will be continuously monitored through the Tempus Oncology Data ecosystem. Citation Format: Stephane Wenric, James M. Davison, Yun E. Wang, Gregory M. Mayhew, Kirk Beebe, Hyunseok P. Kang, Michael V. Milburn, Vincent Chung, Tanios Bekaii-Saab, Charles M. Perou. Purity Independent Subtyping of Tumor (PurIST): Real-world data validation of a pancreatic ductal adenocarcinoma (PDAC) gene expression classifier and its prognostic implications [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr A002.