9503 Background: Pathological complete response (pCR) to neoadjuvant systemic therapy (NST) correlates with survival, and is recognized as a path to regulatory approval in several cancers. Recent trials have reported that neoadjuvant immunotherapy (IT) and targeted therapy (TT) regimens achieve high pCR rates and impressive recurrence-free survival in stage III melanoma, however, the relationship between pCR, relapse-free (RFS) and overall survival (OS) in larger datasets of melanoma patients (pts) remains unknown. Methods: We pooled data from 6 modern NST clinical trials of anti-PD-1 based immunotherapy or BRAF/MEK targeted therapy conducted across institutions participating in the INMC. Pts with RECIST measurable, surgically resectable clinical stage III melanoma who underwent surgery were included. NST regimens included nivolumab (as monotherapy or in combination with ipilimumab), pembrolizumab or dabrafenib+trametinib. Baseline disease characteristics, treatment regimen, pCR and RFS were examined. Results: 184 pts with clinical stage III melanoma (AJCCv7: 100 IIIB, 84 IIIC) completed NST (133 IT, 51 TT) and underwent surgery. Median age was 57y (range 18-87). A pCR was observed in 41% of patients; 51 (38%) with IT and 24 (47%) with TT. Median follow-up post-surgery is 13 mo (95% CI 12-16); 10 mo with IT and 22 mo with TT. 44 (24%) pts have recurred (17 loco-regional, 21 distant, 6 both sites at first recurrence), 18 (14%) after IT and 26 (51%) after TT. 12-month RFS was improved with IT vs TT (83% vs 65%, p < 0.001). For those with pCR, 7% have recurred, 0/51 (0%) after IT, 7/17 (41%) after TT. For those without pCR, 34% have recurred, 18/82 (22%) after IT and 19/27 (70%) after TT. 12-month RFS was improved in those with pCR vs without pCR (95% vs 62%, p < 0.001), including in those with IT (100% vs 72%, p < 0.001) and TT (88% vs 43%, p < 0.001). 16 (9%) patients have died including two who had a pCR, both from TT. Conclusions: Neoadjuvant IT and TT are active regimens in resectable clinical stage III melanoma patients and are associated with high pCR rate. The ability to achieve pCR correlates with improved RFS and remarkably no patient with pCR from immunotherapy has recurred to date.

CIADM is characterized by sudden permanent β-cell failure occurring after immunotherapy. It is distinct from T1D, usually lacks DAA or T1D-associated HLA-risk haplotypes, and is associated with difficult glycemic control from the onset. As such, CIADM represents a new model of auto-inflammatory β-cell failure.

<i>BRAF</i> V600K melanomas appear to benefit less from <i>BRAFi</i>±<i>MEKi</i> than V600E, potentially due to less reliance on ERK pathway activation and greater use of alternative pathways. In contrast, these melanomas have higher mutational load and respond better to immunotherapy.

Aim: Concerns regarding neurocognitive function (NCF) after whole brain radiotherapy (WBRT) exist. This trial compared WBRT versus observation (OBS) following local treatment in patients with one to three melanoma brain metastases. Here, we present the NCF results. Methods: Objective NCF was evaluated in English speakers at baseline, then two‐monthly. Primary outcome was change in delayed recall at 4 months on the Hopkins Verbal Learning Test‐Revised (HVLT‐R). Other NCF tests were also performed. A mixed linear model calculated the effect of intervention on relative raw scores, adjusted for baseline score and time. Cognitive failure was determined by Reliable Change Index; global cognitive impairment was defined as Global Deficit Score &gt;0.5. Analysis was by intention‐to‐treat, with nominal two‐sided significance level 5%. Results: A total of 207 patients were randomised (100 WBRT and 107 OBS) from 31 sites in three countries. NCF testing was completed by 73 WBRT and 70 OBS patients at baseline. Patients had similar characteristics. OBS group had greater relative improvement in HVLT‐R from baseline at every time point. At 4 months, delayed recall declined 2.7% from baseline in WBRT but improved by 20.9% in OBS; overall adjusted average intervention effect 23.6% (95% CI, 9.0‐38.2%; P = .0018). Significant effects were seen between groups at 4 months in HVLT‐total recall and delayed recognition; the overall adjusted average intervention effects were 8.3% (95% CI, 0.4‐16.1%; P = .0397) and 25.0% (95% CI, 14.3‐35.7%; P &lt; .0001), respectively. There were no significant differences in time to cognitive failure (log‐rank P = .44) or proportions with global cognitive impairment at 4 months (OBS 32% vs WBRT 53%; P = .11). Cognitive decline in T‐scores, baseline to 4 months, of 1 SD in at least one NCF test occurred in 24 of 38 (63%) WBRT versus 11 of 25 (44%) OBS (P = .13). Conclusion: Cognitive impairment was common in both groups but greater memory decline occurred in patients receiving WBRT.

CD96 is a novel target for cancer immunotherapy shown to regulate NK cell effector function and metastasis. Here, we demonstrated that blocking CD96 suppressed primary tumor growth in a number of experimental mouse tumor models in a CD8⁺ T cell-dependent manner. DNAM-1/CD226, Batf3, IL12p35, and IFNγ were also critical, and CD96-deficient CD8⁺ T cells promoted greater tumor control than CD96-sufficient CD8⁺ T cells. The antitumor activity of anti-CD96 therapy was independent of Fc-mediated effector function and was more effective in dual combination with blockade of a number of immune checkpoints, including PD-1, PD-L1, TIGIT, and CTLA-4. We consistently observed coexpression of PD-1 with CD96 on CD8⁺ T lymphocytes in tumor-infiltrating leukocytes both in mouse and human cancers using mRNA analysis, flow cytometry, and multiplex IHF. The combination of anti-CD96 with anti-PD-1 increased the percentage of IFNγ-expressing CD8⁺ T lymphocytes. Addition of anti-CD96 to anti-PD-1 and anti-TIGIT resulted in superior antitumor responses, regardless of the ability of the anti-TIGIT isotype to engage FcR. The optimal triple combination was also dependent upon CD8⁺ T cells and IFNγ. Overall, these data demonstrate that CD96 is an immune checkpoint on CD8⁺ T cells and that blocking CD96 in combination with other immune-checkpoint inhibitors is a strategy to enhance T-cell activity and suppress tumor growth.

This study provides the first comprehensive assessment of immune checkpoint receptor expression in any cancer and provides important data for rational selection of targets for trials and predictive biomarker development.

A robust nomogram was developed that more accurately estimates the risk of SN positivity in patients with melanoma than currently available methods. The model only requires the input of 6 widely available clinicopathologic parameters. Importantly, the number of patients undergoing unnecessary SN biopsy would be significantly reduced compared with use of the MSKCC nomogram or the NCCN or ASCO/SSO guidelines, without losing sensitivity. An online calculator is available at www.melanomarisk.org.au.

Abstract INTRODUCTION Glioma is a debilitating and early fatal cancer arising in the glial cells of brain. Glioblastoma, the most aggressive form of gliomas, has a 5-year survival rate of 5% with treatment options limited to surgery, radiotherapy or chemotherapy with temozolomide. OBJECTIVE While radiation and immunotherapies are routinely studied in the murine Gl261 glioma model, little is known about its inherent immune response. In this study we quantified the temporal and spatial localisation of immune cell populations and mediators during glioma development. METHODS Mice were inoculated with 1x106 Gl261 cells at AP0.1mm, ML1.0mm, DV2.6mm Bregma. Tumour morphology, local and systemic immune cell populations were assessed at Day-0, 1, 3, 7, 14, and 21 post-inoculation by MRI, immunohistochemistry for Ki67+ proliferation and CD31+ vessel density; local immune infiltrate by multiplex immunofluorescence (VECTRA®;PerkinElmer); systemic immunity in spleen, bone marrow and peripheral blood by 16-parameter flow cytometry (LSRFortessa™;BD Biosciences); and multiplex immunoassay (Bio-Plex®;Bio-Rad) for plasma cytokines/chemokines. RESULTS From Day-3 tumours were distinguishable with high Ki67+ (&gt; 30%) and increased tissue vascularisation (26.38±1.45 vessels/field; p&lt; 0.05). Ki67 remained high until Day-21 with visible necrotic regions, increased vessel density and lumen area within tumour region. Increasing tumour proliferation/malignancy and vascularisation were associated with significant temporal changes in immune cell populations within the tumour (p&lt; 0.05) and systemic compartments (p=0.02- p&lt; 0.0001). Of note, at Day-14 NK, M1, PMN-MDSCs and M-MDSCs in the tumour infiltrate declined, coinciding with a decrease in 16/24 plasma cytokine/chemokines levels. Tumour infiltrating immune cell populations did not correlate with peripheral blood populations. However, a decrease in plasma cytokine/chemokine levels may indicate ‘immune exhaustion’. CONCLUSIONS The data derived provide baseline characteristics to study changes associated with multi-modal treatment strategies and to sequence therapies to maintain immune modulation. This information will contribute to the identification of novel combination therapies.

0.6–12.7% of patients with primary cutaneous melanoma will develop additional melanomas. Pathologic features of tumors in patients with multiple primary cutaneous melanomas have not been well described. In this large international multi-center case-control study, we compared the clinicopathologic features of a subsequent melanoma with the preceding (usually the first) melanoma in patients with multiple primary cutaneous melanomas, and with those of melanomas in patients with single primary cutaneous melanomas.

Germline genetic variants have been identified, which predispose individuals and families to develop melanoma. Tumor thickness is the strongest predictor of outcome for clinically localized primary melanoma patients. We sought to determine whether there is a heritable genetic contribution to variation in tumor thickness. If confirmed, this will justify the search for specific genetic variants influencing tumor thickness. To address this, we estimated the proportion of variation in tumor thickness attributable to genome-wide genetic variation (variant-based heritability) using unrelated patients with measured primary cutaneous melanoma thickness. As a secondary analysis, we conducted a genome-wide association study (GWAS) of tumor thickness. The analyses utilized 10 604 individuals with primary cutaneous melanoma drawn from nine GWAS datasets from eight cohorts recruited from the general population, primary care and melanoma treatment centers. Following quality control and filtering to unrelated individuals with study phenotypes, 8125 patients were used in the primary analysis to test whether tumor thickness is heritable. An expanded set of 8505 individuals (47.6% female) were analyzed for the secondary GWAS meta-analysis. Analyses were adjusted for participant age, sex, cohort and ancestry. We found that 26.6% (SE 11.9%, P = 0.0128) of variation in tumor thickness is attributable to genome-wide genetic variation. While requiring replication, a chromosome 11 locus was associated (P < 5 × 10-8) with tumor thickness. Our work indicates that sufficiently large datasets will enable the discovery of genetic variants associated with greater tumor thickness, and this will lead to the identification of host biological processes influencing melanoma growth and invasion.

Background A myriad of novel monoclonal antibody based immunotherapies targeting co-stimulating and co-inhibitory receptors have entered clinical trials in melanoma with the aim of increasing response rates and overcoming resistance to standard anti-CTLA-4 and anti-PD-1 immunotherapy. However, little is known about the abundance, co-expression and immune cells enriched for each specific drug target in the various stages of melanoma progression. Therefore, we sought to assess the relative abundance of checkpoint receptors and their expression during melanoma disease progression, as well as the immune cells enriched for each of these molecules.Methods - Multiplex immunofluorescence staining for immune checkpoint receptors (ICOS, GITR, OX40, PD-1, TIM-3, and VISTA) was performed on 95 melanoma biopsies from 41 melanoma patients, including patient matched biopsies for primary, regional lymph node or distant metastases. - Mass cytometry was performed on leukocytes isolated from 18 treatment-naïve melanoma tumors to explore immune subsets enriched for many of the checkpoint receptors currently targeted in clinical trials.Results & Conclusions GITR and OX40 were the least abundant checkpoint receptors in melanoma (p<0.001), with less than 1% of intra-tumoral T cells expressing either marker. TIM-3 and VISTA were mostly expressed on non-T cell populations, with TIM-3 enriched on dendritic cells. Tissue resident T cells (CD69+ CD103+ CD8+) represented a population highly enriched for TIGIT (>70%) and other co-inhibitory receptors but not co-stimulatory receptors. The proportion of GITR+ T cells decreases from primary melanoma (>5%) to patient matched lymph node (<1%, p=0.04) and distant metastases (<1%, p=0.0005). This data will underpin future clinical trial design and provide a rationale for combining these molecules in the clinic.Note: This abstract was not presented at the meeting.Citation Format: Jarem Edwards, Annie Tasker, Inês Pires da Silva, Camelia Quek, Benjamin M. Allanson, Robyn P. M Saw, John F. Thompson, Alexander M. Menzies, Umaimainthan Palendira, James S. Wilmott, Georgina V. Long, Richard Scolyer. Dynamics of T-cell checkpoint receptor profiles during melanoma progression [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 3246.