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9574 Background: The aim of neo-adjuvant therapy in locally advanced or oligometastatic melanoma is to facilitate radical resection, improve outcomes and undertake research to identify biomarkers of response and resistance. The optimal schedule to balance efficacy vs toxicity in dual PD1/CTLA4 blockade regimens remains a matter of debate. We initiated an open- label, single arm study to investigate the Nivo 3/ Ipi 1 schedule as primary treatment of locally advanced or oligometastatic melanoma patients (pts). Methods: Treatment schedule consists in 4 neoadjuvant cycles of Ipilimumab 1 mg/kg and Nivolumab 3 mg/kg every 3 weeks, followed by surgery and adjuvant Nivolumab 480 mg every 4 weeks for 6 cycles. Primary objective is pathological complete remission (pCR) rate, according to Neoadjuvant Melanoma Consortium criteria. Secondary objectives are: safety, feasibility and efficacy; QoL; identification of molecular and immunological biomarkers of response and resistance (somatic genetic drivers, tumor mutational burden, mutational signatures, predicted neoantigens, germline HLA typing, somatic HLA mutations and liquid biopsy); degree of immune activation; evaluation of microbioma Results: From March 2019 to April 2021, 35 pts were included within the trial. All pts completed the treatment program. 6 pts (17%) developed immune-related (IR) G3-4 adverse events (AE): 3 transaminitis, 1 pneumonitis, 1 myocarditis and 1 CPK increase; all of them but one underwent surgery after toxicity resolution. 4 pts (11%) experienced G3-4 non-IR AE. 31 pts underwent surgery after neoadjuvant phase: pCR, near pCR, pathological partial remission (pPR) and pathological no response (pNR) were achieved in 18 (58%), 2 (7%), 4 (13%) and 7 (22%) cases, respectively. 2 pts progressed before surgery and 8 pts progressed during/after adjuvant phase (6/8 in NR at surgery). 4 pts died, 3 after disease progression and 1 for ischemic stroke 5 months after the end of therapy. At 18 months, progression free survival (PFS) and overall survival (OS) were 80 and 85%, respectively (median follow-up: 23 months); non responders (pNR) have a higher risk of relapse or death vs responders (pCR+near pCR+pPR) [HR= 4.11, 95%CI (0.96 -17) adjusted for age, p=0.06]. Conclusions: Our study lends further support to the adoption of the Nivo 3/ Ipi 1 schedule as primary treatment for locally advanced/oligometastatic melanoma, as this regimen achieved a pCR/near pCR rate of 65% with a rate of severe IR-AEs (17%) lower than previously reported in CheckMate 511 trial (34%) using Nivo3/Ipi1 schedule. Available translational data on potential genomic biomarkers of response, gut microbiome and systemic inflammatory landscape evaluated longitudinally during therapy on each patient will be presented. Clinical trial information: 2018-002172-40.

e12570 Background: Hormone receptors and HER2 negative (triple negative, TN) invasive lobular carcinomas (ILCs) are very rare, accounting for 1-2% of all TN breast cancers (BCs). Methods: We extracted data from our prospectively collected institutional database on all consecutive patients (pts) with early stage TN ILC operated at the European Institute of Oncology (IEO) between June 1994 and December 2012. Invasive disease-free survival (iDFS) and cumulative incidence of distant metastases (CI-DM) were calculated. Biological features of these tumors, including molecular intrinsic subtypes based on PAM50 assay, expression of androgen receptor (AR) and mutational status of c-erbB2 gene were also evaluated. Additionally, NGS data of 45 TN ILCs were obtained from 3 large public databases, to confirm mutations in c-erbB2 gene and to identify other recurrently mutated genes. Results: Among 2952 ILCs treated at IEO, 44 (1.5%) were TN and were included in the analysis. All pts received adjuvant chemotherapy. The iDFS rates at 5 and 10 years of follow-up were 47.4% (95% CI, 31.1-62.0) and 29.5% (95% CI, 14.8-45.8), respectively. The corresponding CI-DM percentages were 17.6% (95% CI, 7.6-31.2) and 20.8% (95% CI, 9.5-35.1). The molecular intrinsic subtype was defined through PAM50 for 31 out of 44 TN ILCs: 48% were classified as luminal A, 3% luminal B, 32% HER2-enriched, and only 16% basal-like. The group of pts with luminal A or B tumors had a significantly better CI-DM as compared with pts with non-luminal tumors (i.e. HER2-enriched and basal-like; p=0.003). Luminal tumors expressed AR more frequently than non-luminal tumors (AR≥1% in 96% of luminal tumors versus 53% in non-luminal tumors; p=0.001), and at significantly higher levels (median percentage of AR-positive cells was 80% in luminal tumors versus 15% in non-luminal tumors; p=0.01). Higher AR expression was associated with significantly better iDFS in the whole cohort of TN ILCs (p=0.01), as well as in the group of luminal tumors (p=0.05). 27 TN ILCs of the IEO cohort were analyzed for mutations in c-erbB2 gene, and 9 (33%) harbored mutations. Analysis of the 3 public databases, confirmed c-erbB2 mutations in 9 out of 45 (20%) TN ILCs. All the c-erbB2 mutations found were previously reported to be pathogenetic in BCs and to predict response to neratinib. ErbB signaling and DNA damage response were among the top 10 pathways significantly enriched for mutated genes in TN ILCs. Conclusions: TN ILCs are rare tumors with dire prognosis. Their specific biological features require newly defined targeted therapeutic strategies.

e21114 Background: Patients (pts) with advanced B3 thymoma (B3T) and thymic carcinoma (TC) resistant to chemotherapy have limited treatment options. Treatment with Anti-PD1 showed not negligible toxicity and limited activity, and anti-VEGFR drugs obtained limited and short lasting antitumor responses. No data on combined anti-PD1/PD-L1 with antiangiogenic drugs are available in B3T/TC. We report preliminary results on safety and activity of avelumab combined with axitinib in this pts population. Methods: The CAVEATT is a single arm, multicentric, phase II trial in immunotherapy-naive pts with advanced B3T or TC, progressing after at least one line of platinum based chemotherapy. Prior therapy with antiangiogenic drugs is allowed. Pts received Avelumab 10 mg/kg iv every 2 weeks and Axitinib 5 mg twice a day until progression or toxicity. The primary objective of the study is overall response rate (ORR) by RECIST 1.1; secondary endpoints include ORR by irRC and ITMIG, and QoL by EORTC QLQ-C30. An interim futility analysis is planned after the enrollment of the first 18 patients. If at least 5 out of 18 patients will obtain a PR, the accrual will continue to reach the total number of 33 pts, according with a Simon’s minimax design. Tumor and blood samples are collected at baseline and whenever feasible at disease progression, to identify predictive biomarkers of response and mechanisms of resistance to treatment. Results: 1 pt with B3T and 12 with TC were enrolled from April 2019 to January 2020. Median age was 59 years (range 33-77). 8 pts received ≥2 previous line of therapies, and 6 pts were pretreated with an antiangiogenic drug. The median follow-up was 5.1 months. 10 pts were evaluable for response. The proportions of patients who achieved a partial response (PR) or a stable disease (SD) were respectively 40% (95% CI 17%–69%) and 60% (95% CI 30%–83%). The median PFS was 7.9 months (95% CI 2.5–NA) 12 pts were evaluable for toxicity. Treatment-related adverse events (AE) of grade 1 or 2 occurred in 7 (58%) pts, and the most common was diarrhea (3 pts). Grade ≥3 AEs occurred in 2 (17%) pts: 1 had G3 hyperthension and 1 G3 hand foot syndrome, both leading to axitinib drug reduction. No immune-related AEs (irAEs) were observed. No patient stopped treatment for toxicity, 5 pts stopped for progressive disease, and 8 pts are still on treatment. Conclusions: Preliminary results suggest promising antitumor activity and a good toxicity profile of the combination of axitinib and avelumab in pts with advanced B3T and TC. Accrual is ongoing to reach the target of 33 pts Clinical trial information: 2017-004048-38 .

10038Background: advanced age is associated with comorbidities and impairment of the immune system: these aspects may influence efficacy and tolerability of immune checkpoint inhibitors. Limited da...

e17054 Background: The value of plasma Epstein Barr Virus (EBV) DNA viral load in nasopharyngeal cancer (NPC) patients before treatment correlates with tumor stage and outcome in endemic areas. The aim of our analysis is to explore the role of EBV DNA in a non-endemic setting where just few experiences have been reported. Methods: The medical records of all the patients with positive EBV encoded RNA (EBER) NPC, treated in our institution from 2006 to 2014 with chemotherapy (CT) concurrent with radiation (RT), were retrospectively evaluated. Information about the known prognostic factors, as established in NPC endemic areas, were collected, as well as pretreatment plasma EBV DNA viral load, detected and quantified by real-time PCR. Results: A total of 134 patients were evaluated (median age 48 years; M:F ratio 2:1; stage II 13%, III 31%, IV 56%). Neo-adjuvant CT (TPF scheme) was administered to 78% of the patients. Platinum based CT was delivered concurrently with RT. At a median follow up of 41 months, 25...