Shreenivas, Aditya

4136 Background: The genomic alterations which characterize PDAC holds great promise for novel therapeutic interventions. Constitutive signaling via mutated KRAS is considered the signature pathognomonic alteration in PDAC, less than 10% of patients (pts) have tumors which are KRAS wild type (WT). We retrospectively reviewed our institutional genomic database to characterize PDAC pts with KRAS WT tumors. Methods: We reviewed electronic medical records of PDAC pts who underwent comprehensive genomic profiling (CPG) utilizing Foundation One CDx (50.6%) or TEMPUS (49.4%) between 2015-2020. Demographic and disease characteristics were compared between cohorts using Wilcoxon rank-sum test or chi-square tests. Left truncation at the time of CGP was used to account for the time of entry into the study cohort. Kaplan-Meier method was used for survival curve estimation, and log-rank test was used for between-group comparison. Cox regression was used to adjust for confounders. Results: We identified 235 patients: median age at diagnosis was 65 years and 52% were male. Clinical stages at diagnosis were localized (resectable/borderline resectable), locally advanced, or metastatic in 105 (44.7%), 61 (26.0%), and 69 (29.4%) patients, respectively. KRAS status was mutated in 212 (90%) patients: the most common alterations being G12D (48%), G12V (28%) and G12R (14%). KRAS WT status was noted in 23 (9.8%) pts, actionable genomic alterations in this subgroup are summarized in the table. Baseline demographic and treatment characteristics were similar between patients with KRAS mutated and WT tumors. Of the 23 patients with KRAS WT tumors, 16 (69.6%) completed all planned curative intent therapy compared to 121 (57.3%) of the 212 KRAS mutated pts (p=0.26). Median Overall Survival of patients with KRAS mutated tumors was 18.6 months compared to 44.1 months for WT pts (p=0.03). Adjusting for stage, WT vs. mutated status was associated with a 62% decreased hazard of death (HR 0.38 [0.18-0.83]; p=0.016). Conclusions: Patients with KRAS WT PDAC appear to have a distinct biology compared to those with KRAS mutations, meriting exploration in larger data sets. Further, comprehensive whole genome or transcriptomic characterization of KRAS WT tumors is necessary to identify putative driver alterations as well as actionable therapeutic targets.[Table: see text]

431 Background: Patients (pts) with localized PC do not routinely undergo comprehensive genomic profiling (CGP) unless they develop recurrent or metastatic disease. KRAS is the most frequently mutated gene in PC, however, the impact of different KRAS mutations in localized PC has not been well characterized. We interrogated our genomic database to analyze the KRAS status in PC pts who presented with localized disease at diagnosis (Dx). Methods: We identified PC pts at our institution who underwent CGP utilizing the Foundation One CDx assay and had localized disease at initial Dx; these pts were categorized into resectable/borderline resectable PC (LPC) and locally advanced PC (LAPC). All pts with LPC and LAPC underwent neoadjuvant chemotherapy and chemoradiation prior to possible surgery (all intended therapy - AIT). Tissue from metastatic sites was used for CGP in pts who developed recurrent/metastatic disease before or after completion of AIT. The primary tumor was used for CGP in pts who completed AIT without subsequent relapse or in the absence of adequate metastatic tissue. Effect of each gene on response and survival outcomes was estimated using proportional odds and Cox regression analysis, respectively, adjusting for stage. Results: 75 pts were identified, median age at Dx was 65 years, 59% were male, 65% had a primary tumor in the pancreatic head. 38 (86%) pts with LPC completed AIT compared to 21 (68%) pts with LAPC (p<0.001). KRAS mutation was detected in 95% (71/75) of pts– 94% (67/71) in codon 12 and 6% (4/71) in codon 61. The various KRAS mutations and their association with completion of AIT is summarized in the table. The likelihood of completing AIT did not differ based on KRAS wildtype (WT) vs mutated status (p =1.00), the mutated codon (codon 12 vs. codon 61; p =1.00) or the individual KRAS point mutations (p = 0.7); however, all patients with G12A (N= 1), G12C (N=1), G12L (N=1) and G12R (N=11) mutations completed AIT. KRAS status (mutated vs. WT) and the individual KRAS mutations were not associated with overall survival (OS) after adjusting for stage (p= 0.13 and p = 0.26 respectively). Median OS for patients with LPC and LAPC, was 39 months (mos) and 29 mos respectively. Conclusions: KRAS status and individual KRAS mutations did not have an impact on completing AIT or mOS; however, these findings need to be interpreted with caution due to the inherent biases involved in such analyses. The clinical significance and functional relevance of KRAS G12A, G12C, G12L and G12R mutations, though relatively rare, needs further characterization as well as mechanistic elucidation. [Table: see text]

231 Background: Both peri-operative chemotherapy and neoadjuvant chemoradiation have been shown to improve outcomes in patients (pts) with LA-GEJ CA compared to surgery alone. Rates of post-operative chemotherapy delivery remain suboptimal. Total neo-adjuvant therapy (TNT) in LA-GEJ CA - induction chemotherapy (IC) followed by concurrent chemoradiation (CRT) - may improve systematic delivery of neoadjuvant therapy and result in favorable clinical outcomes. Methods: We retrospectively reviewed medical records of 135 pts with LA-GEJ CA at our institution between 2/2007 and 11/2019; pertinent clinical data were abstracted with Institutional Review Board approval. Patients treated with IC and curative-intent CRT with ≥40 Gy dose of radiation for adenocarcinoma were included in this analysis (N = 59). Doublet or triplet IC regimens utilizing 5-Flurouracil(5-FU), Cisplatin/Oxaliplatin and Docetaxel were commonly administered while combinations of Carboplatin +Paclitaxel or 5-FU + Oxaliplatin were used in CRT. Clinical complete response (CCR) was defined as metabolic imaging and endoscopic biopsies negative for residual malignancy after completion of TNT. Patients were followed from diagnosis to recurrence and overall survival. Survival probabilities were estimated using the Kaplan-Meier method and compared between groups using a log-rank test. Results: Out of 59 evaluable pts, 69% were clinical stage T3, 71% were node positive. 37 pts (63%) underwent surgery, R0 resection rate was 89% (33/37), pathologic complete response (pCR) rate was 19% (7/37). Among the pts who did not undergo surgery, 41% (9/22) opted to forego surgery since they attained a CCR. For the entire cohort, median Disease-Free Survival (mDFS), median Overall Survival (mOS), and 3-yr OS were 2.4 yrs, 4.7 yrs, and 67% respectively. Pts who did not undergo surgery had a mDFS, mOS, and 3-yr OS of 1.5 yrs, 4.2 yrs, and 59% respectively. Median DFS, mOS, and 3-yr OS of patients who underwent surgery were 3.5 yrs, 5.8 yrs and 72% respectively. Patients who achieved a CCR and opted to forego surgery (N = 9) had a 3 -yr DFS of 42% vs 83% for pts (N = 7) who demonstrated a pCR after curative intent tri-modality therapy. (P = 0.0099) Interestingly, the same group that achieved CCR and opted out of surgery had 3yr OS of 89% vs 83% of those who demonstrated a pCR (p = 0.0042). Conclusions: TNT for pts with LA-GEJ CA is associated with high rates of R0 resection as well as excellent DFS and OS compared to historical controls, warranting prospective evaluation. The remarkable DFS and OS in patients who opted to forego surgery due to achieving CCR is reflective of the local and systemic control rendered by this approach. Careful characterization and close longitudinal follow-up of patients who achieve CCR may help identify a subgroup of LA-GEJ CA pts who may benefit from surgery sparing approaches.

e16612 Background: Primary malignant vascular tumors of the liver are rare, aggressive and poorly understood subtypes of liver cancers. In this analysis, we aim to determine the impact of tumor histology and other socio economic factors on survival of these tumors and hepatocellular carcinomas. Methods: Patients with malignant histopathological diagnoses of hepatocellular carcinoma not otherwise specified (HCC NOS), hepatocellular carcinoma with spindle cell (HCC SP), fibrolamellar (HCC F), clear cell (HCC CL), scirrhous (HCC SC) and pleomorphic variants ( HCC PL), combined hepatocellular carcinoma and cholangiocarcinoma (Mixed), hepatic angiosarcoma (AS), hemangioendothelioma (HE), its epithelioid variant (EHE) and hemangiopericytoma (HP) were identified using the SEER (version 2018) database. Overall survival was studied with Kaplan–Meier with the log rank method. Multivariable analysis was performed to assess the impact of race, ethnicity, marital and insurance status on survival of these patients. Results: We analyzed de-identified data of 104502 patients from the year 1973 to 2016 with hepatocellular carcinomas and malignant vascular tumors of liver (including 101851 patients with HCCNOS, 70 with HCC SP, 378 with HCC F, 104 with HCC SC, 593 with HCC CL, 23 with HCC PL, 950 with Mixed, 367 with AS, 36 with HE, 120 with EHE and 10 with HP ) respectively. Median overall survival (OS) of HCC NOS was calculated to be 7 months. Among hepatocellular carcinoma patients HCC F had the longest median OS of 29 months and HCC SP had the shortest median OS of 3months (P < 0.001). Additionally, among patients with malignant vascular tumors, AS had the shortest median OS (1 month) while patients with EHE had the longest median OS of 81 months (P < 0.001). Overall, married and insured patients had a better overall survival than unmarried and uninsured patients (P < 0.04). Conclusions: Malignant vascular tumors of liver are rare in comparison to hepatocellular carcinomas. Spindle cell variant of HCC and liver angiosarcomas carry the worst prognosis and fibrolamellar variant of HCC, hemangioendothelioma (HE) and its epithelioid variant (EHE) have the best prognosis. Insurance and marital status has a positive impact on overall survival of liver cancer patients.

4050 Background: Somatic mutations in KRAS, HRAS, NRAS (extended RAS) and BRAF have prognostic and predictive impact in pts with mCRC. We analyzed the prognostic impact of specific somatic mutations in extended RAS and BRAF. Methods: We retrospectively reviewed the electronic medical records of pts with mCRC at our institution who underwent comprehensive genomic profiling (CGP) utilizing the Foundation One assay. DNA was extracted from clinical specimens and CGP was performed on hybrid-capture, adaptor ligation-based libraries for up to 315 genes plus 47 introns from 19 genes frequently rearranged in cancer. BRAF mutations were classified as class I, II and III according to accepted nomenclature. Fisher’s exact test and Kaplan Meier estimates were used for statistical analyses. This project was approved by the Medical College of Wisconsin Institutional Review Board. Results: 273 pts were identified - median age at diagnosis was 57, 48% were male. Somatic mutations in extended RAS were found in 138 (50%) pts, majority being mutations in KRAS (46%). Among pts with KRAS mutations, codon 12, 13, 61 and 146 mutations accounted for 73%, 11%, 4% and 6% respectively while KRAS G12C mutations accounted for 9%. BRAF mutations were detected in 22 (8%) pts - BRAF V600E and non–V600E mutations accounting for 4.4% and 3.6% respectively. Among pts with BRAF mutations, 17 (77%) were kinase domain mutations, 16 of which could be further classified as class I (12/16), II (1/16) and III (3/16). Median overall survival (mOS) for the entire cohort was 26.4 months (mo). KRAS mutated pts had a mOS of 25.8 mo; pts with KRAS G12C mutation had a mOS of 23 mo compared to 27.1 mo for pts with other KRAS mutations (p < 0.001).Pts with BRAF mutation had a mOS of 26.2 mo; pts with BRAF V600E mutation had a mOS of 14.1 mo compared to 30.6 mo for pts with BRAF non-V600E mutations (p = 0.1). Conclusions: The poor prognosis of pts with KRAS G12C and BRAF V600E mutations compared to pts with other KRAS and BRAF mutations merit further biologic characterization with functional assays. Individualized therapeutic strategies must be conceptualized for mCRC pts with specific RAS/BRAF mutations, considering their widely disparate prognosis and putative downstream signaling mechanisms. Dynamic molecular simulation to understand conformational changes in proteins associated with specific mutations will be pivotal to optimizing precision therapeutic strategies.