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Recent progress in the treatment of advanced melanoma has led to unprecedented improvements in overall survival and, as these new melanoma treatments have been developed and deployed in the clinic, much has been learned about the natural history of the disease. Now is the time to apply that knowledge toward the design and clinical evaluation of new chemoprevention agents. Melanoma chemoprevention has the potential to reduce dramatically both the morbidity and the high costs associated with treating patients who have metastatic disease. In this work, scientific and clinical melanoma experts from the national Melanoma Prevention Working Group, composed of National Cancer Trials Network investigators, discuss research aimed at discovering and developing (or repurposing) drugs and natural products for the prevention of melanoma and propose an updated pipeline for translating the most promising agents into the clinic. The mechanism of action, preclinical data, epidemiological evidence, and results from available clinical trials are discussed for each class of compounds. Selected keratinocyte carcinoma chemoprevention studies also are considered, and a rationale for their inclusion is presented. These data are summarized in a table that lists the type and level of evidence available for each class of agents. Also included in the discussion is an assessment of additional research necessary and the likelihood that a given compound may be a suitable candidate for a phase 3 clinical trial within the next 5 years.

ObjectiveTo describe the prevalence, clinical presentation, and management of rheumatic immune‐related adverse effects (Rh‐irAEs) from immune checkpoint inhibitor (ICI) therapy.MethodsFrom a database of all patients who received any ICI at the Mayo Clinic Rochester, Minnesota campus between January 1, 2011 and March 1, 2018, we retrospectively identified those with Rh‐irAEs, using diagnostic codes, search terms, and manual chart review.ResultsOf the 1,293 patients who received any ICI, Rh‐irAEs were clinically diagnosed in 43. Eighteen patients with Rh‐irAEs who received ICI therapy elsewhere were also analyzed. Clinical syndromes included inflammatory arthritis (n = 34 [prevalence 2%]), myopathy (n = 10), and other rheumatic syndromes (n = 17). Inflammatory arthritis was most commonly polyarticular, and glucocorticoid treatment was required in 26 patients (76%). The mean ± SD duration of treatment was 18 ± 18 weeks. Five patients (15%) also received disease‐modifying antirheumatic drugs, and ICI therapy had to be discontinued in 3 patients (9%). Myopathy was treated with glucocorticoids in all cases (mean ± SD treatment duration 15 ± 17 weeks) and led to 2 deaths and permanent ICI discontinuation in 9 patients (90%). Other syndromes included connective tissue diseases, vasculitis, polymyalgia rheumatica–like syndrome, and flare of preexisting rheumatic disease. Most (71%) were treated with immunosuppression, with 12% requiring ICI discontinuation.ConclusionThis study represents the largest cohort of patients with Rh‐irAEs reported to date. Most patients received long courses of immunosuppressive treatment, although discontinuation of ICI therapy was required in only a minority.

11534 Background: To date, there are no validated blood-based biomarkers of predicting response to PD-1 blockade. We previously reported that Bim is a downstream signaling molecule of the PD-1 pathway, and that measurement of Bim levels in circulating T-cells may predict and monitor responses to anti–PD-1 therapy in melanoma. We have identified the existence of sPD-L1 in cancer patients and showed that the sPD-L1 is biologically active and capable of triggering apoptosis in activated T-cells. Here we evaluated T cell Bim and sPD-L1 in the peripheral blood (PB) as biomarkers of response in a cohort of patients with metastatic melanoma and lung cancer undergoing anti-PD1 therapy. Methods: 60 pts treated with anti-PD-1 had PB collected at baseline and at radiographic tumor evaluation. Frequencies of Bim+ T cells and Bim median fluorescence intensity (MFI) were measured by flow cytometry in gated tumor-reactive CD11ahighPD1+ CD8+ T cells. We also measured levels of sPD-L1 at baseline and serially during treatment with sPD-L1 ELISA. Baseline Bim and sPD-L1 levels and percent change in Bim levels in patients (pts) who had a radiographic response (CR/PR) were compared to those who had progressive disease (PD) at 12 wks. Results: Similarly to previously reported preliminary data, pts with objective response (CR/PR, 15/60) after 4 cycles of anti-PD1 therapy had higher frequency of Bim T cells at baseline compared to pts with PD (16/60) (mean 43% vs. 30%, P = 0.0484). The frequencies of Bim+ T cells decreased significantly after the first 3 months of treatment in responders compared with progressors (mean -16% vs. + 40% P = 0.0111). High baseline sPD-L1 were associated with progression on anti-PD1 therapy (mean 2.8 ng/mL vs. 0.7 ng/mL, p = 0.07, n = 13) and the levels increased by the first tumor assessment in patients resistant to anti-PD-1. Conclusions: Measurements of Bim and sPD-L1 levels may help to select patients who are likely to benefit from anti-PD1 monotherapy versus combinatorial strategies, and provide a new non-invasive way to monitor response to anti-PD-1 blockade. A larger validation study is underway.

e21057 Background: BRAF, NRAS, CDKN2A and P53 mutations are commonly observed pathogenic mutations in cutaneous melanoma. The influence of mutations such as BRAF, NRAS, CDKN2A and P53 on treatment response in the PD1 inhibitor era has not been well defined. Methods: This study included patients with melanoma with a cutaneous or unknown primary. All patients had genomic profiling with the Mayo Clinic 50-gene solid tumor mutation panel. Treatment response to first line immunotherapy with PD1, CTLA-4, or combination PD1/CTLA-4 inhibitors were assessed by response rate and time-to-progression (TTP) rate at 12 months. Each patient outcome was stratified by non-mutually exclusive gene mutation status into BRAF, NRAS, P53, CDKN2A, or quadruple negative (N4) groups. Results: Genomic profiling was performed on 208 patients, of whom 102 received first line immunotherapy. Most patients received a PD1 inhibitor (n = 62), followed by CTLA-4 inhibitor (n = 34), and combination therapy (n = 6). A trend towards improved outcomes was observed in CDKN2A and BRAF mutated patients with worse outcomes noted in P53, N4, and NRAS patients. The percent without progression at 12 months were BRAF 52.2%, CDKN2A 58.2%, NRAS 30.5%, P53 37.7%, and N4 26.7% (see table below). Response rates were BRAF 46.4%, CDKN2A 38.5%, NRAS 22.2%, P53 40.0%, and N4 33.3%. Conclusions: There is a trend towards improved outcomes with immunotherapy in BRAF and CDKN2A mutated patients while P53, NRAS and N4 patients have inferior outcomes. [Table: see text]

e21054 Background: Up to 50% of patients undergoing resection for advanced melanoma experience recurrence. Identification of preoperative prognostic biomarkers is needed to ascertain risk of relapse and guide postoperative management. Lactate dehydrogenase (LDH) represents a strong prognostic factor in unresectable metastatic (stage IV) melanoma, but its relevance in patients with resected stage III or IV disease remains unknown. Methods: We retrospectively analyzed data from patients with stage III and IV melanoma who had undergone complete resection of disease and received follow-up treatment at Mayo Clinic, Rochester between January 1, 2000 and January 31, 2012. Clinical data were collected from electronic records. Survival data were estimated using the Kaplan-Meier method. Associations of preoperative LDH with time to relapse and death were evaluated using Cox proportional hazards regression models and summarized with hazard ratios and 95% confidence intervals. Results: A total of 154 subjects with resectable stage III or IV melanoma were included in the study. Median age at the time of resection was 58; 54 (35.1%) were female. One-hundred sixteen (75.3%) patients were classified as stage III and 38 (24.7%) stage IV. Adjuvant systemic treatment was administered in 75 (48.7%) patients and adjuvant radiation in 32 (20.7%). Median duration of follow-up was 4.0 years. Sixteen (10.3%) patients had preoperative LDH above the upper limit of normal. Each 50-unit increase in LDH was associated with a 15% increased risk of relapse (HR 1.15; p = 0.040) and 23% increased risk of death (HR 1.23; p = 0.001). After adjusting for age, gender, stage, number of sites, adjuvant systemic treatment, and adjuvant radiation, preoperative LDH remained associated with time to death (HR 1.25; p = 0.002). Preoperative LDH greater than the upper limit of normal was associated with increased hazard of death, both with univariate (HR 2.44; p = 0.005) and multivariate (HR 2.17; p = 0.017) analyses. Conclusions: This study supports the role of elevated preoperative LDH as a predictor of inferior outcomes in patients with advanced melanoma. Further study to correlate LDH to outcomes in the era of adjuvant immunotherapy is required.

3034 Background: Unique to modern immune therapy for cancer is that early in the course of treatment, patients frequently exhibit transient tumor enlargement (pseudo-progression, pPROG) due to tumor infiltration by lymphocytes (TIL). Currently, pPROG cannot be reliably distinguished from true tumor progression (PROG). There is a need for biomarker techniques to discriminate pPROG (effect of therapy) and PROG (therapy failure). Nuclear medicine offers radiopharmaceuticals capable of imaging immune cells; images can be fused to evaluate functional and anatomic characteristics of tumors, and potentially discriminate pPROG from PROG. Methods: In our study of metastatic melanoma patients, SPECT/CT imaging with 99mTc-interleukin-2 (99mTc-IL2) was performed to visualize TIL. Images were collected before/after 12 weeks of ipilimumab (IPI) or pembrolizomab (PEMBRO) therapy. The 99mTc-IL2 tracer was synthesized by conjugating succinimidyl-6-hydrazinopyridine-3-carboxylate (HYNIC-NHS) with commercial interleukin-2 (Aldesleukin). HYNIC-IL2 was incubated with tricine, 99mTcO4- (370-740 MBq) and SnCl2. After labelling 99mTc-IL2 was purified by reverse-phase chromatography and diluted in 5% glucose with 0.1% human albumin before injection. Five patients were enrolled in this study. Two patients failed to complete the 12 week 99mTc-IL2 scan due to discontinuation of IPI after: 1) grade 3 colitis and 2) patient refusal for adverse events attributed to IPI. No adverse events attributable to the tracer infusion were reported. Results: Metastatic lesions could be visualized by the tracer. Some lesions decreased in size, while others increased. A positive correlation was found between size and 99mTc-IL2 uptake, before and after therapy, suggesting the potential discrimination of tumor PROG (no 99mTc-IL2 uptake) from pPROG (high 99mTc-IL2 uptake). Immunohistochemical staining for TIL of 99mTc-IL2 positive and negative lesions are illustrated. Conclusions: The results demonstrate feasibility of 99mTc-IL2 imaging as a clinically useful tool capable of discriminating tumor PROG from pPROG. A clinical validation study is in progress. Clinical trial information: NCT01789827.