Soyano, Aixa

Abstract Background: Immune checkpoint inhibitors (ICPIs) have led to dramatic improvement in outcome of several cancers. Program death ligand1 (PD-L1) staining and tumor mutational burden (TMB) have emerged as independent predictive biomarkers of ICPIs in lung cancer. Here we examine the landscape of TMB and PD-L1 expression in breast cancer and present a case of patient with high TMB and PD-L1 negative breast cancer with exceptional response to ICPIs. Methods: Hybrid-capture based comprehensive genomic profiling of 395 cancer related genes using the FoundationOne assay was performed on 14,867 breast carcinomas sequenced in the course of routine clinical care. Ventana (SP-263) PD-L1 status (n=1425) and hormone receptor status was available for a subset of patients. Subgroup analyses were performed based on histological type [invasive lobular carcinoma (ILC, n=740)], molecular subtypes [ER-positive (ER+; n= 1371), HER2-amplified (HER2+; n=1522), and TNBC (n=917)], patient age (≤45, 46-60, ≥61), and local vs. metastatic disease (n=5241 and 6710). Results: Consistent with previous reports, the rates of positive PD-L1 staining are highest in TNBC (14%) and lowest in HER2+, ILC, and ER+ disease (6.0%, 5.1%, 2.3%). Interestingly, the rate of PD-L1 positivity, defined as ≥1% tumor staining, was significantly lower in metastatic disease vs. local disease (6.3% vs. 11.1%; p = 0.005). The frequency of high TMB, defined as >10 mutations/mb, was greatest in ILC and HER2+ disease (13.6% and 9.9%) and lowest in TNBC and ER+ disease (7.0% and 6.9%). Rates of high TMB were associated with increased patient age (3.7%, 9.3%, and 12.8% frequency in patients ≤45, 46-60, and ≥61) and were significantly higher in metastatic vs. local disease (11.1% vs 5.3%; p<2E-23). PD-L1 positive and TMB high populations were not significantly co-occurrent (OR = 1.02, p = 0.87). Similar percentages of PD-L1 positivity were observed in both TMB low (9.3%) and TMB high (9.5%). However, among patients with very high TMB (>20 mut/mb), there was a significant association between TMB and PD-L1 positivity (OR = 2.6, p = 0.023). Nevertheless, even with high cutoff, 79% of the TMB high samples were PD-L1 negative. We also report on a stage IIIb (T4, N2, M0) ER+ HER2- breast cancer patient with high TMB (40muts/mb) and negative PD-L1 IHC who previously progressed on aromatase inhibitor with CDK4/6 inhibitor and chemotherapy but achieved durable complete response of > 1 year with nivolumab in combination with capecitabine. Conclusions: Predictive biomarkers for ICPIs are critical to identify a subset of breast cancer patients who may respond to immunotherapy. TMB high and PD-L1 positivity do not significantly co-occur and the majority of TMB high cases were PD-L1 negative. Nevertheless, this group of patients may still benefit with ICPIs. Further studies are needed to evaluate this subset of patients. Citation Format: Ethan Sokol, Lee Albacker, Aixa Soyano, Ricardo Parrondo, Brenda Ernst, Emmanuel Gabriel, Garrett Frampton, Jeffrey Ross, Siraj Ali, Jon Chung, Saranya Chumsri. Incidence of high tumor mutation burden (TMB) and PD-L1 positivity in breast cancers and potential response to immune checkpoint inhibitors (ICPIs) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4894.

e20599 Background: The anti-PD-1 antibodies nivolumab and pembrolizumab have demonstrated improved overall survival (OS) and progression free survival (PFS) in a subset of patients with metastatic or locally advanced lung cancer (LC). To date, no blood biomarkers have been identified to predict clinical outcome to anti-PD-1 agents. Methods: A retrospective analysis of 52 patients with advanced LC and treated with anti-PD-1 antibodies in a single institution was performed. White blood cell count (WBC), absolute neutrophil count (ANC), absolute lymphocyte count (ALC), absolute neutrophil to absolute lymphocyte count ratio (ANC/ALC), absolute eosinophil count (AEC), and platelet counts at baseline before start of anti-PD-1 antibody were assessed. Kaplan–Meier and Cox regression analysis were done. Results: 48 patients were treated with nivolumab (92.3%) and 4 patients with pembrolizumab (7.7%). Median follow up was 13.6 months and median OS was 26 months. Higher baseline ANC and ANC/ALC ratio significantly correlated with worse clinical outcomes. Patients with baseline ANC > 6060/mm3 had a significantly increased risk of death [hazard ratio (HR) = 2.46; 95% CI 1.12–5.42, P = 0.025] and of progression on anti-PD-1 antibody [HR = 2.41; 95% CI 1.25–4.64, P = 0.009] compared with patients with ANC ≤6060/mm3. Similarly, patients with baseline ANC/ALC ratio ≥ 4.59 had a significantly increased risk of death [HR = 2.41; 95% CI 1.11–5.24, P = 0.027] and of progression on anti-PD-1 antibody [HR = 2.08; 95% CI 1.10–3.95, P = 0.027] compared with patients with ANC/ALC < 4.59. One year survival rate in patients who had ANC < 3390/mm3, ANC 3390-6060/mm3 and ANC > 6060/mm3 were 86.5%, 76.9% and 48.1% respectively. Conclusions: Increased baseline ANC and ANC/ALC were associated with poor PFS and OS in LC patients treated with anti-PD-1 antibodies. Although these findings need to be validated in a large sample size, our data suggested that baseline ANC and ANC/ALC ratio might help the risk stratification and assist treatment strategies. The potential predictive value of peripheral blood biomarkers for clinical outcomes to anti-PD-1 antibody should be further investigated in a prospective study.

e15616 Background: Cholangiocarcinoma (CCA) is a progressively fatal disease with an annual incidence of 1-2 cases per 100,000 people in the USA. Complete surgical resection is the only curative option for CCA. However, the majority of patients (pts) have advanced disease at diagnosis, and those undergoing resection often develop local or distant recurrence. Gemcitabine and Cisplatin remains the only standard chemotherapeutic regimen for advanced CCA. Alternative and improved therapies are critically needed. Gemcitabine/nab-Paclitaxel (GA) is a regimen that has become standard therapy in advanced pancreatic cancer (PDAC). Given the morphologic and histologic similarities between PDAC and CCA, this regimen has been used in advanced CCA, but no data exists regarding its efficacy in this disease. The goal of our study is to evaluate the Mayo Clinic experience with GA for the treatment of metastatic CCA. Methods: We retrospectively analyzed records from adult pts at Mayo Clinic with metastatic cholangiocarcinoma who received at least 2 cycles of GA. Our aims were to assess the progression-free survival (PFS), overall survival (OS) and disease response. Results: We analyzed 9 pts, 3 male and 6 female. The median age at diagnosis was 50 years (range 41-64). Six pts had metastatic disease at diagnosis while 3 underwent surgery with subsequent distant disease recurrence. Pts received a median of 2 lines (range 0-5) of systemic therapy prior to receiving GA, and a median of 2 cycles (range 2-15) of GA. At the time of our analysis, 4 of the 9 pts (44%) had died. The median OS from initiation of GA was 7.3 months (95% CI 1.7- 12.9) and median PFS from initiation of GA was 4.7 months (95% CI 0.48-8.9). The best overall responses using RECIST criteria were: partial response in 1 (11%), stable disease in 5 (55%) and disease progression in 3 (33%) pts. One pt remained on therapy 14.9 months after initiating GA. Conclusions: In our study, the combination of gemcitabine and nab-paclitaxel has demonstrated similar OS and PFS as other systemic therapies. To the best of our knowledge, this is the first report of this regimen in CCA. Ongoing, prospective trials are currently evaluating this regimen in advanced CCA.

530 Background: Therapeutic efficacy of H involves activation of the immune system.Age-dependent progressive deterioration of the immune response is referred as immunosenescence. In HER2+ breast cancer, the effects of aging and the ability of H to activate endogenous anti-tumor immunity is unknown. A previous report from HERA trial showed no significant increase in risk of early recurrence with age (≤ or > 40). We evaluated the long-term outcome of HER2+ patients (pt) related to age and immune landscape. Methods: 1,392 pt from N9831 trial were evaluated. Stromal tumor infiltrating lymphocytes (sTIL) were evaluated in H&E slides. Lymphocyte predominant breast cancer (LPBC) was defined as sTIL ≥ 50%. Molecular TIL (mTIL) and immune subset signatures were evaluated using NanoString research CodeSets. Cox proportional hazard ratio (HR) was used for analysis. Results: There were 1,111 (79.8%) pt > 40 years old (yo) and 281 (20.2%) pt ≤ 40 yo. Younger age was significantly associated with hormone receptor positivity (p 0.00011) and luminal B subtype (p 0.011). With a median follow up of 10.6 years, there was no significant difference in long-term outcome among pt ≤ 40 vs. > 40 yo who received H (HR = 0.88 (0.62-1.24), p = 0.45). Similar findings were observed when age was dichotomized at 50 and 60 yo. While there was no association between sTIL and age, a small but significant increase in mTIL CD45 expression with age (p 0.003) was observed. Similar small increases in cytotoxic cell (p 0.007) and T cell (p 0.015) immune scores were also observed with increasing age. Among pt who received chemotherapy alone, pt > 40 yo with LPBC (n 55) had excellent outcome with 92.4% recurrence free survival (RFS) at 10 years. However, there was no significant difference in RFS among pt ≤ 40 yo with or without LPBC. Conclusions: Among pt treated with H, there was no significant difference in outcome related to age. In contrast to a decline expected from immunosenescence, we observed small but significant increases in mTIL signatures for total lymphocytes, cytotoxic, and T cell subsets. Among patients who received chemotherapy alone, our data suggested that pt > 40 yo with LPBC had excellent prognosis, compared to pt > 40 yo without LPBC.

Abstract Background Treatment of non‐small‐cell lung cancer (NSCLC) has been rapidly advancing over the last decade. Academic centers are considered equipped with better expertise. NSCLC outcome trends in novel therapeutic era and impact of initial treatment at academic centers have not been reported. Methods The National Cancer Database (NCDB) was used to identify NSCLC incident cases from 2004 to 2013. Overall survival (OS) was plotted by year of diagnosis and type of initial treatment center, accounting for several factors available in NCDB. Results A total of 1 150 722 NSCLC patients were included and separated by initial treatment center type (academic: 31.5%; nonacademic: 68.5%). Median follow‐up and OS for all patients were 11.8 months (range: 0‐133.6 months) and 13.1 months (95% CI: 13.08‐13.17), respectively. Median OS improved significantly for those diagnosed in 2010‐2013 (14.8 months [95% CI: 14.7‐14.9]) as compared to 2004‐2009 (12.4 months [95% CI: 12.3‐12.5]) ( P < 0.001). Treatment at academic centers was associated with improved OS (multivariate HR for OS = 0.929 [95% CI: 0.92‐0.94], P < 0.0010). Four‐year OS for academic and nonacademic cohorts was 28.5%% and 22.1%, respectively ( P < 0.001), and the difference was more pronounced in stage I to III NSCLC. Conclusion In this largest analysis, thus far, NSCLC survival has improved over time, and type of initial treatment center significantly influences survival. Identifying and removing barriers to obtaining initial treatment of NSCLC at academic medical centers could improve OS.