PurposeDoxorubicin/cyclophosphamide followed by docetaxel chemotherapy (AC-D) is an intermediate risk factor (incidence of 10%–20%) for febrile neutropenia (FN) in breast cancer. However, the reported incidence of FN while using this regimen was obtained mostly from Western breast cancer patients, with little data available from Asian patients. This study aimed to assess the incidence of FN in Korean breast cancer patients and to describe clinical variables related to FN.MethodsFrom September 2010 to February 2013, data from the Yonsei Cancer Center registry of breast cancer patients who received neoadjuvant or adjuvant chemotherapy with four cycles of AC-D (60 mg/m2 doxorubicin, 600 mg/m2 cyclophosphamide every 3 weeks for four cycles followed by 75 mg/m2 or 100 mg/m2 docetaxel every 3 weeks for four cycles) were analyzed. The incidence of FN, FN associated complications, dose reduction/delays, and relative dose intensity (RDI) were investigated.ResultsAmong the 254 patients reported to the registry, the FN incidence after AC-D chemotherapy was 29.5% (75/254), consisting of 25.2% (64/254) events during AC and 4.7% (12/254) during docetaxel chemotherapy. Dose reductions, delays, and RDI less than 85.0% during AC were observed in 16.5% (42/254), 19.5% (47/254), and 11.0% (28/254) of patients, respectively. Patients with FN events frequently experienced dose reduction/delays, which eventually led to a decreased RDI.ConclusionThe incidence of FN during AC-D neoadjuvant or adjuvant chemotherapy was higher than expected in Korean breast cancer patients. Whether these patients should be classified as a high-risk group for FN warrants future prospective studies.

491 Background: VEGF blockade coupled with cytotoxic chemotherapy can promote an immune-permissive tumor microenvironment that can augment response to PD-L1 inhibition. IMbrave151 (NCT04677504) is a randomized, double-blind, global Phase II study evaluating the efficacy of atezolizumab (atezo), bevacizumab (bev) and cisplatin and gemcitabine (CisGem) as first-line treatment for patients with advanced biliary tract cancer (aBTC). Methods: Patients with previously untreated aBTC were randomized 1:1 to receive atezo (1200 mg every 3 weeks [q3w]) + bev (15 mg/kg q3w) or placebo + CisGem (cisplatin 25 mg/m2 and gemcitabine 1000 mg/m2 on Days 1 and 8 q3w) for up to 8 cycles, followed by atezo (1200 mg q3w) + bev (15 mg/kg q3w) or placebo until disease progression or unacceptable toxicity. Patients were stratified by disease status, geographic region and primary tumor location. The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), objective response rate (ORR), duration of response (DOR), disease control rate and safety. No formal hypothesis testing was performed. Results: In total, 162 patients were randomized to receive either atezo + bev + CisGem (n=79) or atezo + placebo + CisGem (n=83). Median age 63 years, Asia/Rest of World (43/57%), ECOG PS 0/1 (53/48%), intrahepatic/extrahepatic cholangiocarcinoma and gallbladder (54/19/27%), and metastatic/locally advanced stage (82/18%). The HR for PFS was 0.76 (95% CI: 0.51, 1.14). Median PFS was 8.4 months for atezo + bev + CisGem and 7.9 months for atezo + placebo + CisGem; the 6-month PFS rates were 78% and 63%, respectively. The confirmed ORR was 24% for atezo + bev + CisGem and 25% for atezo + placebo + CisGem. DOR ≥6 months was 89% for atezo + bev + CisGem vs 47% for atezo + placebo + CisGem. The incidence of Grade 3 or 4 adverse events was 73% and 74% with atezo + bev + CisGem and atezo + placebo + CisGem, respectively. Median OS is not reached. Conclusions: Both combinations of IMbrave151 showed a manageable safety profile. The aggregate of data suggests that combining atezo with bev and chemotherapy may provide clinical benefit in a subset of patients with aBTC. Follow-up is ongoing for OS. Clinical trial information: NCT04677504 .

4584 Background: Previously, two phase III clinical trials of immune checkpoint inhibitors (ICI) failed to meet their primary endpoints, leading to doubts regarding the clinical activity of ICI monotherapy in patients with aHCC. Here, we comprehensively examined clinicopathological factors and estimated their association with survival outcomes in aHCC patients treated with nivolumab. Methods: A total of 261 eligible patients from 5 high-volume centers who were treated with nivolumab between June 9, 2012 and March 14, 2018 and had measurable diseases were reviewed. We reviewed more than 80 clinicopathological factors and categorized them into 6 areas: 1) demographics (n = 16); 2) baseline laboratory values (n = 19); 3) tumor burden (n = 12); 4) previous treatment (n = 12); 5) treatment response (n = 5); 6) toxicity profiles (n = 18). Their association with survival outcomes were evaluated, and organ-specific response evaluation, adapted from RECIST 1.1, was conducted. Results: Of the 261 patients, 218 (84%) had extrahepatic spread. The median follow-up time was 4.5 months. The median progression-free survival (PFS) and overall survival (OS) were 2.3 months (95% CI, 1.8-2.8) and 6.3 months (95% CI, 5.0-8.2). Objective response rate was 15%. Subgroup analyses revealed that compensated liver function (Child-Pugh score A5/6), surrogate markers for low tumor burden (low AFP, low PIVKA, and low LDH level), inflammatory markers (low C-reactive protein [CRP], low erythrocyte sedimentation rate [ESR], low neutrophil-to-lymphocyte ratio [NLR], high lymphocyte-to-monocyte ratio [LMR]), and low intrahepatic tumor burden were significantly associated with longer OS. A total of 456 individual lesions (liver, n = 249; lung, n = 124; lymph node, n = 35; others such as boner soft tissues, n = 48) were examined. Organ-specific response rates (hepatic tumor, 9%; lung, 25%; lymph node, 37%; others metastasis, 15%) were different, of which intrahepatic tumor was the least responsive organ to ICI treatment in aHCC. Conclusions: Underlying liver function, the tumor extent and burden, and the degree of plasma lymphocytes are crucial for determining tumor response to ICI in aHCC. Antitumor immune response to ICI differs in an organ-specific manner. The hepatic tumors of HCC may be less responsive to nivolumab than extrahepatic lesions.

178 Background: Cancer immunotherapy targeting immune checkpoints are now emerging as a promising therapeutic strategy in various tumors. However, the treatment of T cell non-inflamed tumor which lacks intratumoral T cell infiltrates are still major clinical hurdle. Therefore, drugs that target signaling pathways to increase T cell infiltration in non-inflamed tumor microenvironment (TME) should be investigated. In this study, we aimed to explore the therapeutic potential of STING agonist in murine model of non-small cell lung cancer to overcome immunotherapy resistance. Methods: C57BL/6 mice, which are 6 to 8 weeks of age, were used for the experiment. Mice were injected with Lewis lung carcinoma cells on the right flank. STING agonist (cGAMP) was injected intratumorally. CD8+ and CD31+ cells were detected using immunofluorescence (IF) staining. Gene expressions of tumor microenvironment were analyzed by NanoString RNA sequencing. Flow cytometry (FACS) was performed to detect CD8+, CD4+, Treg and myeloid cell population. Tumor growths were evaluated in combination with anti-PD1 and STING agonist treatment. Results: Local injection of STING agonist effectively delayed tumor growth of LLC. STING agonist increased intratumoral CD8+ T cells and vascular disruption. Expressions of inhibitory checkpoint molecules (PD-1, PD-L1), cytokines (IFN), CD8+ and CD4+ T cells were increased, which showed that anti-cancer immune responses were augmented. Combination treatment of anti-PD-1 antibody and STING agonist synergistically decreased tumor growth. Conclusions: In this study, STING agonist was shown to delay tumor growth and remodel tumor microenvironment in non-inflamed lung carcinoma model. Combination therapy of STING agonist and immune checkpoint inhibitors (ICI) targeting PD-1 synergistically suppressed the growth of lung cancer which is resistant to ICI monotherapy. Collectively, our findings demonstrated that localized STING therapy effectively sensitizes non-inflamed lung cancer to systemic ICI treatment and induces a maximal anti-cancer immune response.

4076 Background: Anti-PD-1 monotherapy elicits various organ-specific immune responses. Although advanced hepatocellular carcinoma (aHCC) showed 20–40% objective response rates (ORR) for cases of extrahepatic lesions in sites such as the lungs or lymph nodes (LNs), only 10% of intrahepatic lesions responded to the monotherapy. The organ-specific responses were due to tumor heterogeneity and differential microenvironments, and may have contributed to the failure of the phase III trials of anti-PD-1 monotherapy for aHCC. Recently, the combination of atezolizumab and bevacizumab (Ate/Bev) as first-line systemic treatment has resulted in survival benefits for patients with aHCC. However, the organ-specific response for this treatment has not been explored. We aimed to evaluate the organ-specific response to Ate/Bev combination therapy in patients with aHCC. Methods: We enrolled patients who received first-line Ate/Bev treatment for aHCC. Eligible patients included those with Child-Pugh A liver function, measurable tumor lesions, and serial image studies available for response evaluation. An independent radiologist reviewed the tumors located in the liver, lungs, LNs, and other sites. Organ-specific response criteria, adapted from RECIST 1.1 and immune-related RECIST, were used. Results: Between May 2020 and June 2021, 124 patients from two Korean cancer referral institutions received first-line Ate/Bev treatment for aHCC. The patient baseline characteristics included: hepatitis B (n = 85, 68.5%), hepatitis C (n = 6, 4.8%), non-viral (n = 33, 26.7%); BCLC stage A/B/C (n = 2, 1.6%/n = 19, 15.3%/n = 103, 83.1%); macrovascular invasion (n = 39, 31.5%); extrahepatic metastasis (n = 75, 60.5%); and AFP >400 ng/ml (n = 39, 31.5%). The median age was 62 years (range: 34–90). With median follow-up duration of 10.1 months, median progression-free survival was 6.8 months (95% CI, 3.6–10.0) and median overall survival was 16.9 months (95% CI, range not available). The ORR was 29.8%. For 260 individual tumor lesions, the liver was the most commonly involved organ (n = 152, 58.5%), followed by the LNs (n = 42, 16.2%) and lungs (n = 24, 9.2%). Ate/Bev treatment induced potent tumor shrinkage in both intrahepatic and extrahepatic lesions: ORR for hepatic lesions was 28.3%; LN lesions, 40.5%; lung lesions, 29.1%; and other metastatic lesions, 19.0%. Further, the organ-specific response rate for intrahepatic tumors decreased as the tumor size increased (36.7%: ≤50 mm, 13.0%: >50 mm). Conclusions: Unlike anti-PD-1 monotherapy, Ate/Bev combination therapy showed favorable responses even in intrahepatic lesions, which are comparable to those in extrahepatic lesions. As such, Ate/Bev may overcome an immune-tolerant hepatic microenvironment in patients with aHCC. (NCT04862949).