Thapa, Bicky

e16260 Background: Therapeutic inhibition of constitutive signaling mediated by mutated KRAS in PDAC remains a challenge except for modest success reported with KRAS G12C inhibition. A combinatorial strategy utilizing simultaneous MEK and autophagy inhibition holds therapeutic promise based on mechanism of action and preclinical data. We described characteristics and outcomes of patients (pts) treated with MEK-inh and HCQ at our institution. Methods: Ten KRAS-mutated advanced PDAC pts were treated with trametinib-HCQ (n = 9) or cobimetinib-HCQ (n = 1) off label due to lack of standard treatment options or toxicity concerns with cytotoxic systemic therapy. Trametinib dose was 2 mg once daily orally, Cobimetinib dose was 20 mg BID orally for 3/4 weeks cycles. HCQ was started at 200 mg BID and up-titrated weekly to 600 mg BID. Description of baseline and treatment (tx) characteristics, safety and efficacy is provided. Results: Median age at diagnosis was 61.3 years, and 7 pts were female. The number of prior lines of tx were 0/1/2/3/4 in 3/2/1/2/2 pts, respectively. KRAS mutations were: G12R/G12D/G12V/Q61H in 6/2/1/1 pts. Median overall survival was 6.6 months (m) in all pts, and 6.6/1.7 m in KRAS G12R/other KRAS (p = 0.31). Median progression-free survival was 5.7/6.2/1.5 m in all/ KRAS G12R/other KRAS (p = 0.16). Among 8 pts with evaluable response, 1 (12%) had partial response ( KRAS G12R) and 4 (50%) stable disease (3/4 KRAS G12R) as best response with disease control rate of 63%/80%/33% in total/ KRAS G12R/other KRAS (p = 0.29). Toxicity data are summarized in table 1. Conclusions: MEK-inh-HCQ demonstrated modest efficacy and manageable toxicities among KRAS G12R PDAC pts. Unlike G12D and G12V mutations in the KRAS gene, G12R is defective of conductive interactions for both PI3Ka and NF1. This ultimately results in a weakened signal being shunted through MAPK cascade and provides a unique opportunity where MEK inh can ablate signaling without the alternate pathways and WT-RAS isoforms compensating. Furthermore, as activation of PI3Ka is known to suppress autophagy, its lack of activation by KRAS G12R further sensitizes cells to HCQ. The combination therapy MEK-inh-HCQ is therefore mechanistically-rationale and warrants the further investigation of KRAS G12R as an actionable biomarker.[Table: see text]

656 Background: Non-neutropenic enterocolitis (NNEC), a potentially fatal toxicity of capecitabine (CAPE), is under-reported in the literature. An institutional review was performed to determine the incidence, clinical course, and outcome of patients developing CAPE-induced NNEC. Methods: After the institutional review board approval, a database search identified patients requiring inpatient care for CAPE-induced diarrhea over a period of 6 years (between 01/2015 and 12/2020). Among the patients requiring hospital admission, patients with radiologic features of enterocolitis were included in the analysis. Data on patient characteristics, imaging study results, clinical course, and outcomes were gathered by electronic chart review. Results: Among the 789 patients treated with CAPE, 25 patients (3%) developed grade 3 or higher diarrhea requiring hospital admission, and 13 out of these 25 patients (1.6 % of patients treated with CAPE) had evidence of enterocolitis on CT scan: ileitis in 7/13 (54%), colitis in 1/13 (8%), and both in 5/13 (38%) patients. The median age of the patient cohort was 64 years (range, 31-81), 8/13 (62%) were female, and all patients were Caucasian. CAPE was administered for the following indications: breast cancer in 6 patients, colorectal cancer in 4 patients, cholangiocarcinoma in 2 patients, and neuroendocrine tumor in 1 patient. ECOG performance status at the time of CAPE initiation was 0 in 7 patients and 1 in 6 patients. Most patients (7/13, 54%) received single-agent CAPE, and the majority (10/13, 77%) developed diarrhea with the first cycle after a median of 21 days (range, 10-50). Patients were hospitalized after a median of 27 days (range, 13-51), and the median hospital stay was 12 days (range, 4-25). None of the 13 patients demonstrated neutropenia at the time of hospital admission. The associated adverse effects at the time of admission included grade 3 abdominal pain in 8 (62%) patients, grade 3 nausea in 7 (54%) patients, and grade 3 vomiting in 3 (23%) patients. Hypokalemia and oral mucositis were present at admission in 6 (46%) and 2 (15%) patients, respectively. Stool studies performed in 11 (85%) patients ruled out infection. Testing for dihydropyrimidine dehydrogenase deficiency performed in 4 (31%) patients was negative. All patients were treated with supportive measures, and 2 (15%) patients required total parenteral nutrition. All but 1 patient recovered fully; 1 patient died due to a condition unrelated to CAPE. Intravenous infusional 5-fluorouracil (5-FU) administration in 3 patients after the recovery was tolerated well. Conclusions: CAPE-induced NNEC is uncommon and generally occurs after the first cycle of therapy. Most patients developing CAPE-induced NNEC recover fully with appropriate supportive measures. Infusional 5-FU-based regimens appear to be safe in this patient group.

596 Background: Genomic alterations (GA) that drive cancer development and predict therapeutic response remain elusive in patients (pts) with KRAS WT PDAC. We interrogated our institutional database to identify actionable GAs in pts with metastatic, KRAS WT PDAC and analyzed the therapeutic impact of matched TT. Methods: We reviewed electronic medical records of KRAS WT PDAC pts (n=24) who underwent comprehensive genomic profiling (CGP) utilizing Foundation One CDx (25.0%) or Tempus (75.0%) between 2015-2021. Duration of response (DOR) was calculated from date of treatment (Tx) initiation to Tx discontinuation. Overall survival (OS) was measured from the date of the diagnosis (Dx) of advanced disease (AD) to death or last follow-up. OS was estimated using the Kaplan-Meier method, with at-risk periods left-truncated at the time of CGP. The effect of covariates on survival was evaluated using Cox proportional hazards regression. Results: Of the 24 KRAS WT pts, 14 (58%) had AD: 8 (57%) pts had metastatic disease at or shortly after Dx, 6 (43%) pts developed metachronous recurrence. Median age at Dx for pts with AD was 65, and 57% were female. Seven of 14 pts with AD (50%) had highly actionable GA (HAGA), (Table). Pts with HAGA demonstrated durable responses to TT (Table) with manageable toxicities. Pts with HAGA had a median OS of 28 mo compared to 5.9 mo for those without (Hazard Ratio = 0.47, p = 0.33). Conclusions: The sustained therapeutic benefit noted with TT matched to HAGA in pts with KRAS WT PDAC underscores the need for systematic interrogation of the somatic genome in PDAC pts. Optimal sequencing of cytotoxic therapy with TT and its impact on modulating clonal selection pressure in pts with KRAS WT PDAC merits prospective evaluation.[Table: see text]

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]