Yoon, Harry H.

4071 Background: Selection of patients for HER2-targeted therapy is based on HER2 analysis in primary EACs. Since EACs metastasize via regional lymph nodes, concordance of HER2 gene amplification results between primary tumors and their metastatic lymph nodes (MLN) is a clinically important issue. Methods: Resected EACs (N = 103) having at least three distinct regional MLNs (total 508 MLNs; median 4 [range 3-11]) were sectioned using routine procedures and tested for HER2 amplification by fluorescence in situ hybridization (FISH). Primary tumors were also evaluated for HER2 protein expression by immunohistochemistry (IHC) and by FISH. Amplification was defined as HER2/CEP17 ≥ 2. IHC was scored as 0, 1+, 2+, or 3+. Primaries whose HER2 status was positive by both FISH and IHC (ie, amplified and IHC3+), or negative by both (ie, nonamplified and IHC0-1+), were selected. HER2 status was compared between primaries and their MLNs (kappa). Results: Concordant HER2 results between primaries and their MLNs were found in 92% (95/103) of EACs (Table; κ = .76 [95% CI .60 - .92]). However, among patients with HER2-positive primaries, 19% (4/21) had HER2-nonamplified MLNs; among these cases, either all MLNs were HER2-nonamplified (n = 2), or both HER2-nonamplified and –amplified MLNs were present (n = 2). Among HER2-negative primary EACs, 5% (4/82) of cases had MLNs that were all HER2-amplified (n = 3) or both HER2-nonamplified and -amplified (n = 1). Conclusions: A patient subset whose primary EACs were HER2-positive (by both FISH and IHC) were unexpectedly found to lack HER2 amplification in corresponding MLNs. Conversely, a subgroup with HER2-negative primaries had HER2-amplified MLNs, and would have been deemed ineligible for HER2-targeted therapy. These preliminary data suggest that evaluating MLNs in resected EACs has the potential to better identify patients who benefit from HER2-targeted therapy. [Table: see text]

4026 Background: Patients (pts) with locally advanced esophageal or gastroesophageal junction (GEJ) adenocarcinoma commonly receive neoadjuvant chemoradiotherapy (chemo-RT). Despite this approach the rate of recurrence remains high. Given the difficulties of postoperative therapy, the efficacy of extended neoadjuvant therapy was assessed. Methods: Eligibility criteria included T3-4,N0 – Tany,N(+) disease amenable to radiation and surgery. Pts were randomized to either arm A (docetaxel 60 mg/m2 day 1 , oxaliplatin [Oxal] 85 mg/m2 day 1, and capecitabine 1250 mg/m2/day days 1-14 x 2 cycles [DOC] followed by 5-FU 180 mg/m2/day continuous IV through radiation + Oxal 85 mg/m2 days 1,15,29 + 50.4 Gy radiation (chemo-RT)) or arm B (chemo-RT alone). Randomization was stratified by ECOG PS (0/1 vs 2) and stage (II vs III/IVA). Primary endpoint was pathologic complete response (PCR) rate, defined as no gross or microscopic tumor identified in the surgical specimen. Interim analysis assessed efficacy and futility of the experimental intervention. Wilcoxon rank sum and Fisher’s exact tests were used to compare clinical/pathologic factors between arms. Results: Baseline and stratification factors were well balanced between arms. Of 42 pts included in the interim analysis (86% male; age [median 63, range 38-88], 100% PS 0/1; 71% stage III; 55% esophagus, 40% GEJ; 36% measurable disease), 4 and 1 pts in arms A and B, respectively, did not have surgery due to death (A, 2), progressive disease (A, 1), alternative treatment (A, 1) or adverse event (B, 1). Among 21 arm A pts, 21, 20, and 19 pts started 1st cycle of DOC, 2nd cycle of DOC and chemo-RT, respectively. All arm B pts received chemo-RT. 33% (7/21) of arm A and 48% (10/21) of arm B pts achieved PCR (p=0.53). Among pts undergoing surgery, 94% (16/17) and 100% (20/20) of arm A and B pts had complete resection (p=0.46). 38% and 24% of arm A and B pts experienced at least one grade 4+ adverse event at least possibly related to treatment (p=0.51). Conclusions: Extended neoadjuvant therapy in pts with locally advanced esophageal or GEJ adenocarcinoma failed to improve the PCR rate. Follow-up in regard to survival and rate of recurrence is ongoing. Clinical trial information: NCT00938470.

2562 Background: Empiric chemotherapy (taxane/platinum) is standard for CUP. Because prognosis is poor, novel approaches are needed. The PI3K/mTOR pathway is frequently dysregulated in cancer. Everolimus (E), an mTOR inhibitor, is approved for multiple malignancies. We performed a phase II study of Pac + Carb + E as first-line therapy in metastatic CUP patients (pts). We additionally determined if a gene expression profiling (GEP) test that identifies tissue of origin (Pathwork Tissue of Origin) could identify responsive pts. (NCT00936702) Methods: Newly diagnosed, untreated CUP pts were eligible. Central pathology review confirmed CUP prior to registration; GEP was performed on formalin fixed tumor tissue. Pac (200 mg/m2), Carb (AUC=6) and E (30 mg once weekly) were delivered every 3 wks until progression or intolerable adverse events (AEs). The primary endpoint was confirmed response, with ≥11 of 50 responses (22%) needed for trial success. Secondary endpoints were OS, progression-free survival (PFS) and AEs. Results: 46 pts (median age 61) received a median 4 cycles (range: 1-33). 39 (85%), 21 (46%) and 1 (2%) experienced ≥1 grade (gr) 3+, 4+, or 5 (sepsis) AE, with gr 3+ hematologic AE most common (74%). Of 44 evaluable pts, 15 had a confirmed response (RR 34%, 95% CI: 21-50%), with a median PFS and OS of 4.1 and 10.1 mos, respectively. Adequate tissue for GEP was available in 36 pts and predicted 10 different sites of origin. In pts with a predicted tissue of origin in which taxane/platinum is standardly used, higher RR and significantly longer PFS and OS were observed compared with pts whose GEP identified a malignancy where taxane/platinum is not standard (Table). Conclusions: In pts with untreated CUP, Carb +Pac +E demonstrated promising antitumor activity. The GEP test identified patients clinically responsive to Carb/Pac/E therapy, and may be useful to select CUP pts for specific antitumor regimens. Clinical trial information: NCT00936702. [Table: see text]

4075 Background: EAC recurrence after surgery with curative intent is believed to carry a uniformly dismal prognosis that may discourage further therapy. To date, the post-recurrence survival of patients has not been examined in EAC. Our aim was to examine site of recurrence in relation to outcome in EAC patients after surgery. Methods: Among EAC patients (N = 796) rendered margin-free at surgery performed at Mayo Clinic, most were T3-4 and lymph node (LN)-positive; none received neoadjuvant therapy. The patient subset who had documented disease recurrence (N = 401) formed the current study population. Cox models were used to examine overall survival (OS) post-recurrence. Results: Among patients with recurrence, median time to recurrence (TTR) was 11 months. Site of recurrence included loco-regional (regional LNs, esophagogastric, anastomosis), chest, abdomen, or distant sites in 97 (27%), 144 (40%), 181 (50%), and 88 (24%) patients, respectively. Most recurrences (66%) were limited to one site. Chest-involved recurrence was significantly associated with improved OS (hazard ratio [HR] 0.78, P = .047), even after adjusting for TTR, number of recurrence sites, tumor pathology, and palliative chemotherapy. This result was confirmed when multivariate analysis was restricted to patients who had only 1 recurrence site (Table) or who had biopsy-proven recurrence (P = .080). In separate models, abdomen-involved (HR = 1.3, P = .016) or bone-involved (HR = 1.6, P= .008) recurrences were independently associated with worse OS. Conclusions: Chest-involved recurrence of EAC independently predicts for improved survival, whereas abdominal and bony sites of recurrence predict for worse outcome. Primary tumor grade and node number were durable prognosticators after recurrence. These novel data provide useful prognostic information and have the potential to influence clinical decision-making. [Table: see text]

4009 Background: HER2 expression in upper digestive cancer is reported to be heterogeneous, which substantially affects interpretation of HER2 positivity in the clinic. Yet the frequency and prognostic impact of HER2 genetic heterogeneity and polysomy 17 (poly17) are unknown in EAC. Methods: HER2 amplification (fluorescence in situ hybridization) and protein expression were examined in untreated surgical EAC specimens (N = 661) at Mayo Clinic. HER2 genetic heterogeneity was defined per ASCO/CAP as amplification (HER2/CEP17 ratio ≥ 2) in 5-50% of cancer cells; poly17 refers to ≥ 3 copies of chromosome 17. Most tumors were T3-4 (68%) or lymph node (LN)-positive (73%). Cox models were used to assess disease-specific (DSS) and overall survival (OS). Results: HER2 amplification was detected in 117 of 661 EACs (18%), of which 20 (17%) showed HER2 heterogeneity. HER2 heterogeneous tumors had a significantly higher frequency of poly17 and high tumor grade. HER2 heterogeneity by amplification vs expression were correlated. Since heterogeneity was limited to HER2-amplified tumors, survival analysis was stratified by amplification status. In multivariable analysis, only HER2 heterogeneity and metastatic LN number were prognostic (Table). Conclusions: Among HER2 amplified EACs, 17% show HER2 heterogeneity, which is associated with increased poly17 and independently predicts 2-fold higher risk of cancer-specific death. Among HER2-nonamplified cases, poly17 is independently associated with worse survival. These novel findings demonstrate aggressive subgroups in HER2-amplified and -nonamplified EACs that have important implications for HER2 analysis and evaluation of benefit from HER2 targeted therapy. [Table: see text]

TPS468 Background: Trastuzumab (T), a monoclonal antibody (mAb) targeting HER2, is standard of care palliative 1st-line therapy for advanced HER2+ GEJ/GC patients (pts). M, an Fc-engineered anti-HER2 mAb, targets the same HER2 epitope but with higher affinity for both 158V (high binding) and 158F (low binding) alleles of activating Fc receptor CD16A. M coordinately enhanced both innate and adaptive immunity, including antigen-specific T-cell responses to HER2. PD-1 and LAG-3 are T-cell checkpoint molecules that suppress T-cell function. MGA012 (INCMGA00012) is a humanized, hinge-stabilized, IgG4 κ anti-PD-1 mAb blocking binding of PD-L1 or PD-L2 to PD-1. MGD013 is a humanized Fc-bearing bispecific tetravalent protein that binds to both PD-1 and LAG-3, inhibiting their respective ligand binding. We previously reported that a CTX-free regimen of M+PD-1 blockade was well tolerated in GEJ/GC pts, and induced a 30% objective response rate (ORR). This was 2- to 3-fold greater than in historical controls with checkpoint inhibitors alone. This registration-directed trial assesses efficacy, safety, and tolerability of M+checkpoint inhibition ± CTX in metastatic/locally advanced, treatment-naïve, HER2+ GEJ/GC pts. Methods: This is a 2-cohort, adaptive open-label phase 2/3 study. The first single arm, CTX-free cohort A evaluates M+MGA012 in HER2+ (immunohistochemistry [IHC] 3+) and PD-L1+ (excluding microsatellite instability high) pts. After 40 pts are evaluated for response/safety, 60 more pts will be enrolled if the threshold for continuation is met. In randomized cohort B, HER2+ (IHC 3+ or 2+/fluorescent in situ hybridization+) pts are enrolled irrespective of PD-L1 status. Part 1 randomizes pts to 1 of 4 arms (50 pts each): control arm (T+CTX) or 1 experimental arm (M+CTX; M+CTX+MGA012; M+CTX+MGD013). CTX is investigator’s choice XELOX or mFOLFOX-6. Part 2 consists of control (T+CTX) vs 1 experimental arm (M+CTX) + either MGA012 or MGD013, depending on results from part 1; with 250 pts each. The primary efficacy endpoint for cohort A (both parts) is ORR per RECIST 1.1; for cohort B part 2 it is overall survival.

TPS462 Background: Esophageal squamous cell carcinoma (ESCC) is the predominant histological subtype of esophageal cancer, particularly in Asian countries. Inhibition of the PD-1/PD-L1 axis has demonstrated antitumor activity in patients with advanced unresectable or metastatic ESCC. Tislelizumab, an investigational humanized IgG4 monoclonal antibody with high affinity and binding specificity for PD-1, was engineered to minimize binding to FcγR on macrophages in order to abrogate antibody-dependent phagocytosis, a mechanism of T-cell clearance and potential resistance to anti-PD-1 therapy. Results from early phase clinical studies suggest tislelizumab, as a single agent or in combination with chemotherapy, was generally well tolerated and had antitumor activity in patients with solid tumors, including ESCC. Methods: This global, phase 3, randomized, placebo-controlled, double-blind study (NCT03783442) is designed to evaluate the efficacy and safety of tislelizumab plus chemotherapy as first-line treatment of unresectable, locally advanced recurrent or metastatic ESCC. Adult patients with histologically confirmed unresectable ESCC, or locally advanced recurrent/metastatic disease with a ≥6 month treatment-free interval, are eligible; palliative radiation administered > 4 weeks from study initiation is allowed. Patients who received prior anti-PD-(L)1, anti-PD-L2, or first-line therapy are ineligible. Patients (n≈480) will be randomized 1:1 to receive tislelizumab 200 mg IV every 3 weeks (Q3W) plus investigator-chosen chemotherapy (ICC) or placebo plus ICC. ICC options include: platinum (plat; cisplatin 60-80 mg/m2 or oxaliplatin 130 mg/m2 IV Q3W) + 5-FU 750-800 mg/m2 by continuous IV infusion over 24 hours for 5d Q3W; or plat + capecitabine 1000 mg/m2 orally BID for 14d Q3W; or plat + paclitaxel 175 mg/m2 IV Q3W. Progression-free and overall survival are primary endpoints; secondary endpoints include objective response rate, duration of response, and health-related quality of life. Safety will be assessed by monitoring adverse events, physical examinations, vital signs, and electrocardiograms. This study is actively enrolling. Clinical trial information: NCT03783442.

362 Background: Most pts with mGEA do not respond to ICI or ramucirumab/paclitaxel (RAM/TAX). Emerging data suggest that ICI may potentiate subsequent therapy (Tx). In KN059 we unexpectedly observed durable responses in 2 pts on RAM/TAX after ICI (PMID 29674442). We examined if ICI impacts efficacy of subsequent RAM/TAX in a larger cohort and explored alterations in the tumor microenvironment. Methods: All pts with mGEA at Mayo Clinic (MN, AZ, FL) who received RAM/TAX (2014-19) were included. We compared best objective response rate (ORR: complete [CR] or partial response [PR]) per RECIST1.1 and overall survival (OS) in pts who received RAM/TAX with (Group A) vs without (Group B) immediately preceding PD-1 blockade. Chi square and multivariate logistic and Cox regression were used. We adjusted for total lines of Tx received and the line of Tx in which RAM/TAX was given, to control for potential differences in the biology of heavily treated pts or those receiving RAM/TAX as 2nd vs 3rd line Tx. We also adjusted for age and ECOG PS. Results: In total 87 pts met inclusion criteria. In the 19 pts (Group A) who received RAM/TAX (usually as 3rd line Tx) after progression on ICI, there was a 77% relative risk reduction of death after initiation of RAM/TAX compared to the 68 pts (Group B) who received RAM/TAX (usually as 2nd line) without preceding ICI (median OS 15.0 vs 7.6 mo; HR 0.23; P < .001). The ORR was also significantly higher (58% vs 18%; P < .001) including the CR rate (16% vs 1%; P = .006). Two CRs in Group A are ongoing (10 - 34 mo). Of note, 95% of Group A pts did not respond to ICI, and all had irRECIST progression on ICI. Immunofluorescent analysis from a responder showed 65-fold reduction (post vs pre-Tx) in intratumoral density of immunosuppressive FOXP3+ Tregs, with preserved density of antitumor CD8+ T cells. Conclusions: Higher than expected efficacy was observed on RAM/TAX when immediately preceded by ICI, suggesting ICI may enhance efficacy of subsequent anti-VEGFR/taxane therapy. This serial immunotherapy combination may be a novel option for pts with primary resistance to ICI and will be tested prospectively in a new randomized phase 2 trial (NCT04069273).

167 Background: Previous studies have reported high TILs are a favorable prognostic factor in stage II CC. However, whether the impact of TILs on overall survival (OS) differs among pts who did or did not receive ADJ is still to be determined. We assessed the prognostic value of CD3+ TILs in pts with stage II CC according to whether they received ADJ or not (no-ADJ). Methods: Pts treated with curative surgery for stage II CC (2002-2013) were identified through the Santa Maria alle Scotte Hospital database. CD3+ TILs at the invasive front, center of tumor, and stroma, were determined by immunohistochemistry and manually quantified as the rate of TILs/total tissue areas. High TILs (H-TILs) was defined as > 20%. Pts were classified as high or low TILs (L-TILs) and ADJ or no-ADJ. Cox models were used to assess OS with hazard ratio estimates (95% CI). Results: Of the 678 pts included (356 deaths), 137 (20%) received ADJ while 541 (80%) did not. ADJ comprised fluoropyrimidine +/- oxaliplatin. Median follow-up was 8.5 years. The distributions of the 4 groups were: 16% (L-TIL/ADJ), 64% (L-TIL/no-ADJ), 5% (H-TIL/ADJ), 15% (H-TIL/no-ADJ). Compared to H-TILs/no-ADJ, ADJ pts had a significantly longer OS (P < .0001) regardless of the TILS rate while L-TILs/no ADJ had significantly shorter OS and higher risk of death (HR = 1.41; 95% CI, 1.06-1.88; P < .0001) [See table]. On multivariable analysis, adjusting for perforation, obstruction, T-stage, grade, < 12 lymph nodes resected, lymphovascular and perineural invasion, the adverse prognostic impact of L-TILs (vs H-TILs) in no-ADJ pts was confirmed (HR = 1.36; 95% CI 1.02, 1.82; P = .0373). Conclusions: Low CD3+ TILs rate was independently associated with shorter OS in stage II CC pts who did not receive ADJ, but was not prognostic among pts who had ADJ. These data suggest a potentially different impact of TILs in chemo-treated vs -untreated stage II CC which could affect clinical decision making. [Table: see text]

4009 Background: Interim analysis of a global, phase 2 KEYNOTE-059 study (NCT02335411) reported manageable safety and promising antitumor activity for pembro alone or pembro + chemo in pts with G/GEJ cancer. Here we report long-term efficacy and safety data of all cohorts. Methods: Pts with recurrent or metastatic G/GEJ adenocarcinoma were enrolled in 3 cohorts. Cohort 1 pts (PD-L1–positive or –negative) received pembro alone after ≥2 prior lines of therapy. Cohort 2 pts (PD-L1–positive or –negative) received pembro + cisplatin (80 mg/m2 day 1) + 5-fluorouracil (800 mg/m2 days 1-5 Q3W) or capecitabine (in Japan only, 1000 mg/m2 twice daily) as first-line. Cohort 3 pts (PD-L1–positive, combined positive score ≥1% using the PD-L1 IHC 22C3 pharmDx assay) received pembro alone as first-line. All pts received pembro 200 mg Q3W for up to 2 years. End points included safety, ORR, DOR, and OS. Results: At data cutoff (Aug 8, 2018), median (range) follow-up was 6 (1-38), 14 (2-40), and 21 (2-36) months for cohorts 1 (n = 259), 2 (n = 25), and 3 (n = 31), respectively. In cohort 1, confirmed ORR (95% CI) was 11.6% (8-16) overall, 15.5% (10-22) in PD-L1–positive, and 6.4% (3-13) in PD-L1–negative tumors. In cohort 2, confirmed ORR was 60.0% (39-79) overall, 73.3% (45-92) in PD-L1–positive, and 37.5% (9-76) in PD-L1–negative tumors. In cohort 3, confirmed ORR was 25.8% (12-45). Median (range) DOR in months was 16.1 (2-35+), 4.6 (3-37+), and not reached (2.1-32.5+) in cohorts 1, 2, and 3, respectively. OS at 1 year/2 years was 24.6%/12.5%, 52%/32%, and 63.6%/40.1% in cohorts 1, 2, and 3, respectively. In cohorts 1, 2, and 3, grade 3-5 treatment-related adverse event (TRAE) incidence was 46 (18%), 20 (80%), and 8 (26%) respectively. TRAEs led to discontinuation in 6 (2%) and 3 (12%) pts in cohorts 1 and 2, respectively, and to death in 2 (1%) pts in cohort 1. No TRAEs led to discontinuation or death in cohort 3. Conclusions: These updated results demonstrate manageable safety, durable clinically meaningful activity of pembro in heavily pretreated pts, and promising efficacy of first-line pembro (alone or + chemo) in pts with advanced G/GEJ cancer. Clinical trial information: NCT02335411.