Chakrabarti, Sakti

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]

AbstractThrough our involvement in KEYNOTE‐059, we unexpectedly observed durable responses in two patients with metastatic gastroesophageal adenocarcinoma (mGEA) who received ramucirumab (anti‐VEGFR‐2)/paclitaxel after immune checkpoint inhibition (ICI). To assess the reproducibility of this observation, we piloted an approach to administer ramucirumab/paclitaxel after ICI in more patients, and explored changes in the immune microenvironment. Nineteen consecutive patients with mGEA received ICI followed by ramucirumab/paclitaxel. Most (95%) did not respond to ICI, yet after irRECIST‐defined progression on ICI, all patients experienced tumor size reduction on ramucirumab/paclitaxel. The objective response rate (ORR) and progression‐free survival (PFS) on ramucirumab/paclitaxel after ICI were higher than on the last chemotherapy before ICI in the same group of patients (ORR, 58.8% vs 11.8%; PFS 12.2 vs 3.0 months; respectively). Paired tumor biopsies examined by imaging mass cytometry showed a median 5.5‐fold (range 4‐121) lower frequency of immunosuppressive forkhead box P3+ regulatory T cells with relatively preserved CD8+ T cells, post‐treatment versus pre‐treatment (n = 5 pairs). We then compared the outcomes of these 19 patients with a separate group who received ramucirumab/paclitaxel without preceding ICI (n = 68). Median overall survival on ramucirumab/paclitaxel was longer with (vs without) immediately preceding ICI (14.8 vs 7.4 months) including after multivariate analysis, as was PFS. In our small clinical series, outcomes appeared improved on anti‐VEGFR‐2/paclitaxel treatment when preceded by ICI, in association with alterations in the immune microenvironment. However, further investigation is needed to determine the generalizability of these data. Prospective clinical trials to evaluate sequential treatment with ICI followed by anti‐VEGF(R)/taxane are underway.

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.

The current standard treatment for patients with early-stage colon cancer consists of surgical resection, followed by adjuvant therapy in a select group of patients deemed at risk of cancer recurrence. The decision to administer adjuvant therapy, intended to eradicate the clinically inapparent minimal residual disease (MRD) to achieve a cure, is guided by clinicopathologic characteristics of the tumor. However, the risk stratification based on clinicopathologic characteristics is imprecise and results in under or overtreatment in a substantial number of patients. Emerging research indicates that the circulating tumor DNA (ctDNA), a fraction of cell-free DNA (cfDNA) in the bloodstream that originates from the neoplastic cells and carry tumor-specific genomic alterations, is a promising surrogate marker of MRD. Several recent studies suggest that ctDNA-guided risk stratification for adjuvant therapy outperforms existing clinicopathologic prognostic indicators. Preliminary data also indicate that, aside from being a prognostic indicator, ctDNA can inform on the efficacy of adjuvant therapy, which is the underlying scientific rationale for several ongoing clinical trials evaluating ctDNA-guided therapy escalation or de-escalation. Furthermore, serial monitoring of ctDNA after completion of definitive therapy can potentially detect cancer recurrence much earlier than conventional surveillance methods that may provide a critical window of opportunity for additional curative-intent therapeutic interventions. This article presents a critical overview of published studies that evaluated the clinical utility of ctDNA in the management of patients with early-stage colon cancer, and discusses the potential of ctDNA to transform the adjuvant therapy strategies.

Biliary tract cancers (BTCs) are a heterogeneous group of adenocarcinomas that originate from the epithelial lining of the biliary tree. BTCs are characterized by presentation with advanced disease precluding curative surgery, rising global incidence, and a poor prognosis. Chemotherapy is the mainstay of the current treatment, which results in a median overall survival of less than one year, underscoring the need for novel therapeutic agents and strategies. Next-generation sequencing-based molecular profiling has shed light on the underpinnings of the complex pathophysiology of BTC and has uncovered numerous actionable targets, leading to the discovery of new therapies tailored to the molecular targets. Therapies targeting fibroblast growth factor receptor (FGFR) fusion, isocitrate dehydrogenase (IDH) mutations, the human epidermal growth factor receptor (HER) family, DNA damage repair (DDR) pathways, and BRAF mutations have produced early encouraging results in selected patients. Current clinical trials evaluating targeted therapies, as monotherapies and in combination with other agents, are paving the way for novel treatment options. Genomic profiling of cell-free circulating tumor DNA that can assist in the identification of an actionable target is another exciting area of development. In this review, we provide a contemporaneous appraisal of the evolving targeted therapies and the ongoing clinical trials that will likely transform the therapeutic paradigm of BTC.

AbstractTrial InformationClick here to access other published clinical trials.Lessons LearnedTrifluridine/tipiracil (FTD/TPI) shows promising antitumor activity in heavily pretreated patients with advanced biliary tract carcinoma, including patients with 5-fluorouracil refractory tumors. FTD/TPI has an acceptable safety profile and should be studied further in patients with advanced biliary tract carcinoma after progression on standard first-line therapy.BackgroundPatients with advanced biliary tract carcinoma (BTC) refractory to first-line therapy lack an established second-line option. Trifluridine/tipiracil (FTD/TPI) has activity in both fluoropyrimidine-sensitive and -resistant tumors, which led us to conduct a single arm phase II trial to evaluate the safety and efficacy of FTD/TPI for patients previously treated for advanced BTC.MethodsPatients with advanced BTC previously treated with at least one line of chemotherapy were enrolled and treated with FTD/TPI until disease progression or unacceptable toxicity. The primary endpoint target was to have at least 6 patients who were progression free and alive at 16 weeks among 25 evaluable patients. Secondary endpoints included overall survival (OS), overall response rate (ORR), progression-free survival (PFS), and toxicity.ResultsOf 27 evaluable patients, 59.3% received at least three prior lines of therapy, and 81.5% had previous exposure to fluoropyrimidine. Eight (32%, 95% confidence interval [CI], 14.9%–53.5%) patients were progression free at 16 weeks in the primary analysis population (n = 25), which met the predefined efficacy criteria. Median PFS and OS were 3.8 (95% CI, 2–5.8 months) and 6.1 (95% CI, 4.4–11.4 months) months, respectively. No objective responses were seen. There were no unexpected safety signals noted.ConclusionFTD/TPI demonstrated promising antitumor activity, with acceptable toxicity, in heavily pretreated patients with advanced BTC.

3532 Background: Colorectal cancer with dMMR display heterogeneity in the extent of intratumoral T-cell infiltration which may explain their variable responsiveness to PD-1 blockade. We examined the association of intratumoral CD3+ and CD8+ T-cell densities (TCD) with objective response rate (ORR) and response duration in patients with dMMR mCRCs receiving pembrolizumab (PEM). Methods: Record review was performed on 12 patients with dMMR mCRC treated with PEM (200 mg intravenously every 3 weeks) after failure of prior chemotherapy [median no. of regimens was 1 (range 1-4)] between 01/2015 and 12/2017. CD3+ and CD8+ TCDs were analyzed in the primary tumor core (CT) and at the invasive margin (IM) by immunohistochemistry and automated image analysis to determine density score (0 to 100) for each T-cell subtype and compartment (Ventana Medical Systems, Inc.). Patients were categorized as 1) responders [CR (complete response) + PR (partial response)] vs. non responders [SD (stable disease) + PD (progressive disease)] per RECIST version 1.1, and 2) by duration of response (< or > 12 months). Results: Median follow-up post PEM was 19.5 (9-41) months. Responders included 2 CR and 5 PR; non-responders included 4 SD and 1 PD. The ORR and median time to response were 58.3% (7/12) and 12 weeks (range 9-40), respectively. CD3+ and CD8+ TCD scores were higher in responders vs. in non-responders as well as in patients who had disease control for > 12 months; differences were greatest for CD8+ CT (Table). Conclusions: Among patients treated with PEM, data suggest higher intratumoral CD3+ and CD8+ TCDs in responders versus non-responders and in those with a longer duration of disease control. If confirmed, TCDs may potentially predict responsiveness to PD-1 blockade in dMMR mCRCs. [Table: see text]

393 Background: Clinicopathological features and the outcomes of patients with fibrolamellar hepatocellular carcinoma (FLHCC) are not clearly defined. Methods: Data were collected by retrospective chart review on 42 patients with FLHCC treated between 1990 and 2017 at the Mayo Clinic. Clinicopathological characteristics, response to treatment, recurrence pattern and survival were analyzed. Results: Of 42 patients (17 males and 25 females; median age at diagnosis 22 years, range 15 to 39), 10 patients (23%) had stage I disease and 32 patients (77%) had stage II to IVB disease. All 10 patients with stage I disease and 21 of 32 patients with stage II-IVB disease underwent resection at presentation. In stage I patient group, 6 patients experienced recurrence with a median time to recurrence of 30.5 months, resulting in a 5 year overall survival (OS) of 86%. Patients with stage II to IVB disease who underwent resection (n=21) at presentation had a median OS of 32.5 months and 5 year OS of 44%. In the upfront surgery group, 71% of the patients experienced recurrent disease. The median OS of patients with unresectable disease (n=11) was 10 months. Systemic therapy was given to 17 patients which included sorafenib, FOLFOX (5-fluorouracil/leucovorin and oxaliplatin), gemcitabine plus oxaliplatin, single agent adriamycin or gemcitabine, capecitabine plus interferon alfa, gemcitabine plus cisplatin, cisplatin plus adriamycin and nivolumab . Sorafenib was given to 9 patients and 4 patients achieved stable disease (SD) with duration ranging from 5 months to 5 years. One programmed cell death receptor positive-1 patient had a durable complete response after 2 months of therapy with nivolumab. Conclusions: In FLHCC, surgical resection was associated with prolonged OS. However, recurrences were common after the surgery. Limited benefit was derived from the systemic treatment. In rare cases, therapy with a checkpoint inhibitor may provide a viable treatment option.