Markovic, Svetomir N.

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.

Abstract Malignant pleural mesothelioma is a disease primarily associated with exposure to the carcinogen asbestos. Consistent with this carcinogenic exposure, cytogenetic analyses have identified multiple recurrent structural chromosomal abnormalities in this malignancy, but more recent high-throughput sequencing evaluations of point mutations suggest that there is a low mutational burden in mesothelioma. Since tumor mutational burden has been correlated with responses to treatment with immune checkpoint inhibitors such as nivolumab, it was not consistent that patients with mesothelioma and low mutation burdens would have similar response rates in clinical trials with immune checkpoint inhibitors as patients with non-small cell lung cancer which is associated with a high mutation burden. In order to reconcile these differences, and given the potential for an improved understanding of the molecular pathogenesis of mesothelioma to improve therapeutic options, we used mate-pair sequencing (MPseq) and RNA sequencing (RNAseq) to understand how structural variants affect the transcriptome. MPseq differs from standard next generation sequencing approaches by tiling the whole genome with larger fragments (2-5kb) to reliably detect structural variants such as insertions, deletions and rearrangements. Amongst 22 mesothelioma specimens there were 1535 chromosomal rearrangements (median 41, range 3-298 per specimen), that resulted in junctions or novel fusions of non-coding DNA or genes. Six-hundred thirty-seven of these rearrangements (median 22, range 5-103 range per specimen) resulted in novel fusions of genes. Many of these inter- or intra-chromosomal rearrangements were consistent with a pattern of chromoanagesis such as chromoplexy or chromothripsis. Chromosomal rearrangements detected by MPseq were used to guide analysis of RNAseq data and revealed that these chromosomal junctions resulted in the expression of 179 novel amino acid sequences (median 5, 0-51 range per specimen). To determine whether transcription of chromosomal rearrangement-related junctions have neoantigenic potential, we used in silico tools to determine whether any of the expressed junctions contained peptides that could be presented by patient-specific HLA molecules. The top candidate rearrangement-related peptides with neoantigenic potential bound patient-specific HLA molecules nearly as well or as well as a positive control in competitive binding assays. Our findings represent the discovery of potential neoantigen expression driven by structural chromosomal rearrangements. These results may have implications for the development of novel therapeutic strategies, the selection of patients to receive immunotherapy, and blood-based treatment monitoring strategies. Citation Format: Aaron S. Mansfield, Tobias Peikert, James B. Smadbeck, Julia B. Udell, Farhad Kosari, Stephen J. Murphy, Hongzheng Ren, Vishnu V. Serla, Janet L. Schaefer Klein, Giannoula Karagouga, Faye R. Harris, Carlos Sosa, Sarah H. Johnson, Wendy Nevala, Svetomir N. Markovic, Aaron O. Bungum, Eric S. Edell, Haidong Dong, John C. Cheville, Marie Christine Aubry, Jin Jen, George Vasmatzis. Rearrangement-related peptides with neoantigenic potential in malignant pleural mesothelioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5726.

Abstract Background The treatment of metastatic melanoma has been revolutionized by developments in targeted therapy and immunotherapy. BRAF/MEK inhibitors, blockade of cytotoxic T-lymphocyte antigen 4 (CTLA-4) and programmed death (PD-1/L1) receptor have shown durable anti-melanoma effects. The optimal sequence strategy of targeted therapy and immunotherapy in metastatic BRAF-mutated melanoma patients (pts) is unknown and no treatment guidelines exist. Therefore, we report a single-institution experience of different treatment approaches using targeted therapy and immunotherapy and its impact on outcomes. Methods Pts with BRAF-mutated metastatic melanoma treated with targeted therapy and immunotherapy from 2012 to2017 were analyzed. Six groups were identified based on treatment strategy: (1) 1st line BRAF/MEK inhibitors followed by 2nd line immunotherapy; (1.1) 1st line BRAF/MEK inhibitors followed by 2nd line immunotherapy in combination with BRAF/MEK inhibitors (triple therapy);(1.2) same as group 1 followed by triple therapy as 3rd line; (2) 1st line immunotherapy followed by 2nd line BRAF/MEK inhibitors; (2.1) 1st line immunotherapy followed by 2nd line triple therapy; (2.2) same as group2 followed by triple therapy as 3rd line. All time-to-event analysis was calculated using the Kaplan-Meier method and Wilcoxon test. Results Forty four pts were included. The median age at diagnosis was 49 years (range 21-73), 24 (54%) pts were females and 19 (43%) developed brain metastases during their disease course. BRAF V600 mutation was seen in all pts except in 1 pt with p.N581S mutation. The preferred 1st line targeted therapy was dabrafenib/trametinib used in 17 (94%) out of 18 pts, while ipilimumab was the preferred 1st immunotherapy used in 11 (42%) out of 26 pts. For 2nd line therapy, DT was used in 19 (90%) out of 21 pts, while pembrolizumab was used in 16 (69%) out of 23 pts. For 3rd line, DT was used in 5 (83%) out of 6 pts, while pembrolizumab was used in 6 (100%) out of 6 pts. DT was usually the first choice for patients with high burden disease or brain metastases. The most common approach strategy was immunotherapy followed by targeted therapy (group 2), the median duration of treatment was 11 and 19 weeks respectively; for pts started on targeted therapy followed by immunotherapy (group 1), the median duration of treatment was 17 and 14 weeks respectively. (Table 1) Time-to-next therapy (TTNT) following 1st line treatment was similar in pts treated with targeted therapy (median 23 weeks [95% CI: 15-31]) or immunotherapy (median 26 weeks [95% CI: 10-33], p=0.94). Following 2nd line treatment, the TTNT for pts treated with targeted therapy was 18 weeks (95% CI: 4-38), immunotherapy 18 weeks (95% CI: 13-19) and triple therapy 22 weeks (95% CI: 13-41), p=0.48. A trend towards better overall survival (OS) from frontline therapy was seen in pts who received immunotherapy (1st line) followed by targeted therapy (2nd line) (median 7 years [95% CI: 2.7-7.08]) compared to those who received targeted therapy (1st line) followed by immunotherapy (2nd line) (median 2.3 years [95% CI: 1.3-NR], p=0.09. Interestingly, patients who received salvage chemotherapy had significant longer OS in those treated initially with immunotherapy (median 7 years [95% CI: 3.2-7.08]) (n=6) compared to patients started on targeted therapy (median 2 years [95% CI: 0.6-2.4], p=0.03) (n=5). Conclusion A trend towards longer OS was seen in pts treated with 1st line immunotherapy followed by 2nd line targeted therapy with a median therapy time of 11 and 19 weeks respectively. No difference in TTNT was seen with the use immunotherapy, targeted therapy or triple therapy when used as 1st or 2nd line. The significant longer OS benefit with f 1st line immunotherapy was only seen in patients who received chemotherapy later in their treatment course. Table 1.Treatment Characteristics by GroupMedian duration of therapy in weeksGroup(n)1st line therapy(median)2nd line therapy(median)3rd line therapy(median)Totalmedian (range)Chemotherapy (n)1(n=9)Targeted therapy(17)Immunotherapy (14)N/A52 (13-134)51.1(n=7)Targeted therapy(25)Triple therapy (19)Any*(43)69 (22-118)11.2(n=2)Targeted therapy(60)Immunotherapy (16)Triple therapy (21)96 (81-111)12(n=18)Immunotherapy(11)Targeted therapy(19)Any*(24)48 (16-120)52.1(n=4)Immunotherapy(17)Triple therapy (16)Any*(9)41 (25-69)02.2(n=4)Immunotherapy(19)Targeted therapy(16)Triple therapy (19)61 (54-73)1* include any treatment regimen such as immunotherapy, targeted therapy or chemotherapy Citation Format: Jesus Vera-Aguilera, Jonas Paludo, Narjust Duma, Marcella Tschautscher, Cecilia Yu, Svetomir Markovic. A clinical insight into therapeutic sequence in advanced melanoma [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr LB-A32.

Background and ObjectivesTo describe the patterns of failure in patients with in‐transit (IT) melanoma undergoing surgical excision.MethodsA retrospective review of patients who underwent their first IT lesion(s) resection between May 2005 and September 2014. Cumulative incidence of local failure (new lesion within 2 cm of IT resection) was estimated. Associations between clinicopathologic characteristics, local failure, and any recurrence were analyzed.ResultsOne hundred and thirty patients presented to our institution with IT disease over the study period and met the inclusion criteria. The 2‐year cumulative incidence of local failure was 19.5%. Twenty‐four patients developed disease within 2 cm of the resected IT disease; however, only eight were isolated local events. Cumulative incidence of local failure and of any disease differed with respect to less than 1 year disease‐free interval (DFI) from primary melanoma to first IT event, and having greater than 1 IT lesion at presentation. Incidence of local failure was not found to differ with respect to gross margin greater than 5 mm, after adjusting for DFI and greater than 1 IT lesions.ConclusionsPatients with greater than 1 IT lesion and a DFI less than 1 year are at a higher risk of failure after surgical excision of a first IT event. Very few failures were isolated local disease within 2 cm of the IT resection scar, regardless of IT excision margin.

Abstract Using personalized peptide vaccines (PPVs) to target tumor-specific nonself-antigens (neoantigens) is a promising approach to cancer treatment. However, the development of PPVs is hindered by the challenge of identifying tumor-specific neoantigens, in part because current in silico methods for identifying such neoantigens have limited effectiveness. In this article, we report the results of molecular dynamics simulations of 12 oligopeptides bound with an HLA, revealing a previously unrecognized association between the inability of an oligopeptide to elicit a T cell response and the contraction of the peptide-binding groove upon binding of the oligopeptide to the HLA. Our conformational analysis showed that this association was due to incompatibility at the interface between the contracted groove and its αβ–T cell Ag receptor. This structural demonstration that having the capability to bind HLA does not guarantee immunogenicity prompted us to develop an atom-based method (SEFF12MC) to predict immunogenicity through using the structure and energy of a peptide·HLA complex to assess the propensity of the complex for further complexation with its TCR. In predicting the immunogenicities of the 12 oligopeptides, SEFF12MC achieved a 100% success rate, compared with success rates of 25–50% for 11 publicly available residue-based methods including NetMHC-4.0. Although further validation and refinements of SEFF12MC are required, our results suggest a need to develop in silico methods that assess peptide characteristics beyond their capability to form stable binary complexes with HLAs to help remove hurdles in using the patient tumor DNA information to develop PPVs for personalized cancer immunotherapy.