Efficacy of immune checkpoint inhibitors for the treatment of advanced melanoma in patients with concomitant chronic lymphocytic leukemia

BACKGROUND

Immune checkpoint inhibitors (ICIs) have revolutionized the management of advanced melanoma (AM). However, data on ICI effectiveness have largely been restricted to clinical trials, thereby excluding patients with co-existing malignancies. Chronic lymphocytic leukemia (CLL) is the most prevalent adult leukemia and is associated with increased risk of melanoma. CLL alters systemic immunity and can induce T-cell exhaustion, which may limit the efficacy of ICIs in patients with CLL. We, therefore, sought to examine the efficacy of ICI in patients with these co-occurring diagnoses.

PATIENTS AND METHODS

In this international multicenter study, a retrospective review of clinical databases identified patients with concomitant diagnoses of CLL and AM treated with ICI (US-MD Anderson Cancer Center, N = 24; US-Mayo Clinic, N = 15; AUS, N = 19). Objective response rates (ORRs), assessed by RECIST v1.1, and survival outcomes [overall survival (OS) and progression-free survival (PFS)] among patients with CLL and AM were assessed. Clinical factors associated with improved ORR and survival were explored. Additionally, ORR and survival outcomes were compared between the Australian CLL/AM cohort and a control cohort of 148 Australian patients with AM alone.

RESULTS

Between 1997 and 2020, 58 patients with concomitant CLL and AM were treated with ICI. ORRs were comparable between AUS-CLL/AM and AM control cohorts (53% versus 48%, P = 0.81). PFS and OS from ICI initiation were also comparable between cohorts. Among CLL/AM patients, a majority were untreated for their CLL (64%) at the time of ICI. Patients with prior history of chemoimmunotherapy treatment for CLL (19%) had significantly reduced ORRs, PFS, and OS.

CONCLUSIONS

Our case series of patients with concomitant CLL and melanoma demonstrate frequent, durable clinical responses to ICI. However, those with prior chemoimmunotherapy treatment for CLL had significantly worse outcomes. We found that CLL disease course is largely unchanged by treatment with ICI.

Randomized phase II study of neoadjuvant checkpoint blockade for surgically resectable undifferentiated pleomorphic sarcoma (UPS) and dedifferentiated liposarcoma (DDLPS): Survival results after 2 years of follow-up and intratumoral B-cell receptor (BCR) correlates

LBA11501

Background: We conducted a randomized, phase II non-comparative trial evaluating the efficacy of neoadjuvant ICB [nivolumab or ipilimumab/nivolumab] in patients (pts) with surgically resectable retroperitoneal DDLPS or extremity/truncal UPS treated with concurrent neoadjuvant radiation therapy (XRT, UPS only). Methods: As of February 28 2022, all pts have a minimum follow-up of 2 years from the start of ICB treatment. Progression-free survival (PFS) and overall survival (OS) were calculated using Kaplan Meier method. The association of pathologic response (percent hyalinization and viable tumor at surgery) with PFS and OS was assessed using Cox univariate models. Comparison of survival curves was done by log-rank method. The intratumoral BCR repertoire was evaluated by bulk tumor RNA sequencing with TRUST4 algorithm, on biopsy specimens collected at baseline. Description of the intratumoral BCR repertoire included diversity by inverse Simpson index, and clonal distribution by Gini coefficient. High and low categories were defined by median values. Results: At a median follow-up of 31 months (interquartile range [IQR]=27-43) since start of ICB treatment, the median PFS was not reached (NR) in UPS (IQR=19-NR) and 18 months for DDLPS (IQR=8-NR), with 13 pts experiencing relapse (2 UPS, 11 DDLPS) and 2 pts who had progressive metastatic disease on treatment (1 UPS, 1 DDLPS). Five pts died of disease relapse (1 UPS, 4 DDLPS) and the median OS was NR. There was no association between percent hyalinization at surgery and PFS (Hazard Ratio [HR]=0.98, p=0.12) or OS (HR=0.99, p=0.60) nor between percent viable tumor at surgery and PFS (HR=1.00, p=0.62) or OS (HR=1.00, p=0.67). There was no association between RECIST response and PFS (p=0.67) or OS (p=0.67). The median BCR heavy chain (IgH) clonal counts detected at baseline was 2,536 per sample (IQR=82-7,680), and the median BCR light chain (IgL) clonal count was 8,870 per sample (IQR=306-30,214). Pts with higher intratumoral BCR clonality and diversity at baseline tended to have longer PFS (Table). High BCR IgH clonality was significantly associated with OS (p=0.02) with consistent trends in each histotype (DDLPS: p=0.06; UPS: p=0.25). Conclusions: Survival results demonstrate efficacy of ICB with XRT in UPS but there is a crucial need to define better predictive markers of survival after neoadjuvant therapy. Further characterization of the BCR repertoire is ongoing and will be presented at the meeting. Clinical trial information: NCT03307616. [Table: see text]

Long-term outcomes of a phase II trial of neoadjuvant immunotherapy for advanced, resectable cutaneous squamous cell carcinoma of the head and neck (CSCC-HN)

9519

Background: In a pilot phase II trial, we investigated the use of neoadjuvant immunotherapy to induce a pathologic response in patients with stage III/IV (M0) cutaneous squamous cell carcinoma of the head and neck (CSCC-HN). Here, we report the long-term outcomes according to pathologic response. Methods: Patients with newly diagnosed or recurrent stage III/IV (M0) (AJCC 8th Ed) CSCC-HN were treated with 2 doses of cemiplimab 350 mg intravenously every 3 weeks prior to surgery. The primary endpoint was overall response rate (ORR) per RECIST v1.1. Secondary endpoints included safety, pathologic response, disease-free and overall survival. Results: Of 20 patients enrolled, 7 (35%) had recurrent disease and 12 (60%) were stage IV on presentation. Neoadjuvant immunotherapy was generally well-tolerated and there were no surgical delays. Adverse events (AEs) were observed in 7 (35%) patients; 1 (5%) grade 3 diarrhea, 6 (30%) ≤ grade 2 AEs. ORR by RECIST was 30%. However, 85% (17/20) achieved a pathologic response (≤50% viable tumor), with pathologic complete response (pCR) in 11 (55%), major pathologic response (MPR, ≤10% viable tumor) in 4 (20%) and pathologic partial response (pPR, >10% and ≤50% viable tumor) in 2 (10%). Patients with a pCR did not receive planned radiotherapy after surgery. Patients who did not have a pathologic response (> 50% viable tumor) either progressed and died (1, 5%) or developed recurrence (2, 10%) despite surgery and adjuvant radiation or chemoradiation. At a median follow up of 34.5 months (range: 7.7-42.7), none of the patients who achieved a pathologic response have recurred. Conclusions: Consistent with other cancer types, pathologic response to neoadjuvant immunotherapy is durable in patients with advanced, resectable CSCC-HN. Adjuvant radiation therapy may be spared in patients who achieve a pCR and warrants further investigation. Clinical trial information: NCT03565783.

Androgen receptor blockade promotes response to BRAF/MEK-targeted therapy

9523

Background: Treatment with BRAF+/-MEK inhibition (BRAF+/-MEKi) has revolutionized treatment in melanoma and other cancers, but resistance is common and innovative treatment strategies are needed. Sexual dimorphism in response to BRAF+/-MEKi have been noted, but mechanisms behind this are poorly understood and hormonal modulation has not been well-studied in this setting. Methods: We examined outcomes by sex in five clinical cohorts of patients (pts) (total n = 792, 362 female, 430 male) with BRAF-mutated melanoma who were treated with BRAF/MEKi in either the neoadjuvant or metastatic setting. Rates of major pathologic response (MPR), clinical benefit (CB), progression free survival (PFS) relapse-free survival (RFS) and overall survival (OS) were assessed. Translational research studies were performed on available pre- and on-treatment tumor samples (n = 27 pts) including RNA sequencing and profiling androgen receptor (AR) expression. Parallel studies were performed in preclinical models to assess the effect of sex and AR modulation on response to BRAF+/-MEKi. Results: In this study, improved rates of MPR, CB, PFS and OS were observed in female vs male pts. Specifically, female patients treated with neoadjuvant BRAF+MEKi showed significantly higher rates of MPR (66% v. 14%, p = 0.001), and improved RFS (64% versus 32% at 2 years, p = 0.021) vs male pts in the neoadjuvant setting (n = 51). These findings were not observed in a 2nd smaller trial of pts (n = 35), but were validated in a cohort of pts with unresectable metastatic melanoma treated with BRAF+MEKi (n = 69), with significantly higher rates of CB (80% v. 68%, p = 0.022) and PFS (12 v. 7 months, p = 0.003) in female vs male pts. Data from several published trials was analyzed (COMBI-D and METRIC trials), demonstrating improved PFS/OS at 2 years in female vs male pts treated with combined BRAF/MEKi (n = 211; p = 0.03 and, p = 0.04) and in female vs male pts treated with MEKi monotherapy (n = 206; p = 0.04 and p = 0.002), but not in female vs male pts treated with BRAFi monotherapy (n = 211; p = 0.21 and 0.095). Significantly higher expression AR expression was observed in available on- vs pre-treatment samples from male pts (p = 0.01), suggesting that treatment with BRAF/MEKi may induce AR expression in tumors. Findings were recapitulated in several preclinical models, and treatment with pharmacologic inhibitors of AR signaling (enzalutamide) in combination with BRAF/MEKi was associated with significantly enhanced anti-tumor activity in both male and female mice (p = 0.003 and p < 0.0001). Conversely, systemic treatment with testosterone was associated with significantly impaired tumor control in male and female mice (p = 0.021 and < 0.001). Conclusions: These data suggest that AR blockade may promote BRAF/MEKi response in melanoma, warranting further investigation in clinical trials. The impact of AR signaling, and modulation should be studied in MAPK-targeted therapy across other cancer types.

Baseline tumor genomic and gut microbiota association with clinical outcomes in newly diagnosed glioblastoma (GBM) treated with atezolizumab in combination with temozolomide (TMZ) and radiation

2006

Background: Checkpoint inhibitor (CPI) therapy has demonstrated overall limited efficacy in the treatment of GBM. Sixty newly diagnosed GBM patients unselected for MGMT status underwent treatment with concurrent atezolizumab with radiation therapy and TMZ followed by adjuvant atezolizumab and TMZ (NCT03174197). Clinical data has been reported previously. Methods: Genomic (WES with somatic mutation and SCNA determination N = total 42 samples, 33 baseline, 9 TP-2), transcriptomic (RNA seq N = total 72 samples, 54 baseline, 18 TP-2), and metagenomic sequencing of fecal samples (N = total 45 samples, 26 pre samples, 13 post RT samples, six 6m samples) analyses were conducted on pre-treatment samples. Findings were correlated with clinical outcome including OS and PFS. Twenty of the 60 patients underwent re-resection for suspected recurrent disease of which nine patients had WES and RNA seq performed successfully on paired pre and post treatment samples. Results: Somatic mutation, copy number and ploidy profiles were consistent with known aberrations in GBM. An unsupervised molecular network-based stratification of pre-treatment tumor mutations resulted in patients being grouped in 3 clusters with survival difference. Patients with GBM harboring an EGFR aberrancy were associated with a relatively worse mOS following treatment compared to patients with tumors enriched with PTEN alterations, while patients with IDH1 mutations had the longest mOS. Gene set enrichment analysis of gene expression in tumors from patients ( < mOS vs ≥mOS) identified genes associated with lymphocyte activation and immune response in patients with longer survival (p < 0.01) Unsupervised hierarchical clustering of bacterial taxa demonstrated two distinct clusters with significant difference by OS. Survival analysis and Analysis of Compositions of Microbiomes with Bias Correction (ANCOM-BC) revealed distinct taxa associated with OS ( Ruminococcus spp.) and response to treatment ( Eubacterium spp.), respectively. Conclusions: In this small CPI-treated GBM cohort, WES, SCNA and RNA seq identified pre-treatment tumor features that separated patients by survival. The fecal microbiome observations in our GBM cohort warrants further investigation. Clinical trial information: NCT03174197.

A single-center experience of 98 patients (pts) with regionally metastatic Merkel cell carcinoma (MCC) of known (MCCKP) and unknown (MCCUP) primary at presentation

9576

Background: MCC is a rare skin cancer historically associated with poor survival rates and which is increasing in incidence. A small number of retrospective series suggest that MCCUP may be associated with better prognosis than MCCKP while others report worse outcomes. Recent advances in immunotherapy have changed the multimodal treatment landscape and outcomes of advanced MCC pts. We describe our experience with the management and outcomes of pts presenting with regional MCC metastasis of known and unknown primary origin. Methods: A retrospective review of pts with clinical regional disease at MCC diagnosis treated at our institution from 3/2003-3/2021 was performed. Clinicopathologic variables and outcomes were assessed. Overall survival (OS), recurrence-free survival (RFS) and progression-free survival (PFS) were estimated by the Kaplan Meier method. Results: Of 98 pts with regional disease on exam at presentation, 56 (57%) had MCCUP and 42 (43%) had MCCKP. Median follow-up from diagnosis to last follow-up or death was 33 months. Pts were generally older (MCCUP vs MCCKP: 68.7 vs 73.1 years), male (MCCUP vs MCCKP: 82% vs 74%) and Caucasian (MCCUP vs MCCKP: 84% vs 83%). Over half the pts had a history of another malignancy (MCCUP vs MCCKP: 52% vs 60%) with 9% and 14% being immunocompromised at diagnosis, respectively. After completion of staging workup, MCCUP pts had earlier stage disease at presentation compared with MCCKP pts (stage IIIA: 80% vs 55%, IIIB: 5% vs 31%, IV: 15% vs 14%, respectively). The cervical nodal basin was most commonly involved in MCCUP pts while regional disease was more varied in MCCKP pts (MCCUP vs MCCKP: cervical 54% vs 28%, axillary 15% vs 33%, inguinal 33% vs 3%, inguinal and pelvic 0% vs 11%, in transit 0% vs 14%). Formal lymphadenectomy (LND) was performed in 27 (48%) and 18 (43%) of MCCUP and MCCKP pts, respectively. Of these pts, 33% and 50% received neoadjuvant systemic therapy, most commonly immunotherapy; 70% and 55% received adjuvant radiotherapy. MCCUP pts had better outcomes compared to MCCKP pts (Table), with longer RFS in pts who underwent LND (not reached [NR] vs 13.1 months) as well as longer PFS in pts who did not undergo LND (17 vs 9 months) with longer OS in both subgroups (LND: NR vs 102.7 months; no LND: 74.4 vs 48.7 months). Conclusions: MCCUP patients with regional disease on exam at presentation have improved survival compared to MCCKP. Current stage III survival estimates may underestimate survival in patients with resectable disease. [Table: see text]

Identifying gut microbial signatures associated with B cells and tertiary lymphoid structures (TLS) in the tumor microenvironment (TME) in response to immune checkpoint blockade (ICB)

2511

Background: While ICB has significantly improved clinical outcomes across several cancer types, only 15-20% of patients develop a durable response. Thus, novel and targetable biomarkers are needed. There is increased appreciation of the role of the gut microbiome, and TLS and B-cells in the TME in response to ICB. Here, we investigate the association between these two determinants of response in patient specimens from three randomized phase 2 neoadjuvant ICB trials of nivolumab +/- ipilimumab (melanoma (MEL; NCT02519322; n=23), non-small-cell lung cancer (NSCLC; NCT03158129; n=31), sarcoma (SARC; NCT02301039; n=17). Methods: Patients were categorized as responders (R) or non-responders (NR) based on major pathologic response, as defined in each histotype (MEL and NSCLC viable tumor ≤10%; SARC hyalinization>30%). Baseline fecal samples were profiled via 16S rRNA gene sequencing from all three cohorts to assess the composition of patient gut microbiomes. Transcriptional profiles of biopsies collected pre-ICB for MEL and SARC, and post-ICB for MEL, SARC, and NSCLC were used to assess TLS (CXCL13, CCL18, CCL19, CCL21) and B-cell (PAX5, CD79B, CR2, MS4A1) signatures in the TME, by calculated mean values of normalized gene expressions. Comparison between samples were carried out using the Wilcoxon signed-rank test. Results: There were 21 R overall (NSCLC n=9; MEL n=9; SARC n=3). Despite significant differences in alpha and beta diversity across cohorts, relative abundance of Ruminococcus was significantly higher in R (p=0.003; NSCLC p<0.001; MEL p=0.049; SARC p=0.7). B-cell signature was significantly higher post-ICB in R (R vs NR, post, TLS p=0.13; B-cell p=0.003), with consistent trends in each cohort. Longitudinal evaluation of transcriptional profiles showed that expression of TLS and B-cell signatures increased with treatment in R (pre vs post, MEL and SARC; TLS p=0.0098; B-cell p<0.001) but not NR (pre vs post; TLS p= 0.87; B-cell p= 0.15), with consistent trends in sarcoma and melanoma subgroups. Combined correlative analysis with matched specimen showed that patients with higher pre-ICB relative abundance of Ruminococcus (above median) had significant increase in B-cell signatures (pre vs post, MEL and SARC; TLS p=0.052; B-cell p=0.002) which was not seen in patients with low abundance (below median) of Ruminococcus (pre vs post, MEL and SARC; TLS p=0.56; B-cell p=0.69). Conclusions: Unifying signatures in the gut microbiome are associated with response to ICB and increased B-cell infiltration and TLS formation in the TME. We expect these findings to energize mechanistic studies and new microbiome-based interventional approaches to improve clinical outcomes with ICB. Clinical trial information: NCT02519322, NCT03158129, NCT02301039.

Evaluating the impact of perioperative antibiotic prophylaxis on the microbiome in patients with cutaneous malignancy

TPS9602

Background: Preoperative antibiotic prophylaxis is commonly used to reduce surgical site infections (SSIs). However, the rate of SSIs following surgical procedures classified as clean is only 2-3%. Overuse of antibiotics is associated with several potential adverse effects, including dysregulation of the gut microbiome. Disruption of the composition and function of the native gut microbiota, referred to as dysbiosis, has been implicated in a number of inflammatory and autoimmune disorders, as well as gastrointestinal (GI) and non-GI cancers. Recent studies have demonstrated that antibiotics have a profound and persistent effect on the gut microbiota, as evidenced by diminished overall abundance and diversity, as well as alteration of community composition that includes a decreased relative abundance of bacteria in the Ruminococcaceae family. In melanoma, diversity of gut microbiota and relative abundance of Ruminococaceae have been linked to improved survival and enhanced response following immune checkpoint blockade. In this study, we seek to determine the impact of preoperative prophylactic antibiotic use on the gut microbiome in patients following surgery for stage I or II melanoma. Methods: In this non-comparative randomized pilot trial, the impact of prophylactic antibiotic use at the time of surgical intervention on gut microbiome diversity and composition will be studied. Patients diagnosed with clinical stage I or II melanoma undergoing wide excision with or without lymphatic mapping and sentinel lymph node biopsy are randomized 1:1 to either receive preoperative cefazolin or no preoperative antibiotics. Stool samples and peripheral blood are collected before surgery, the day of surgery (optional), on post-operative day 3 (optional), and 2 weeks and 3 months following surgery. The primary endpoint for the study is change in microbiome alpha diversity at 2 weeks following surgery. Secondary endpoints are change in relative abundance of microbes at 2 weeks and 3 months after surgery and SSI rates according to whether or not prophylactic antibiotics were administered at time of surgery. Exclusion criteria include recent antibiotic use (within 3 months), allergy to beta-lactam or cephalosporin antibiotics, increased risk of infection due to medical comorbidity or use of immunosuppressive medication. Enrollment began in October 2021. As of January 2022, 22 of 30 patients have been accrued to ensure complete sample collection for 20 patients. Study findings may inform a larger trial evaluating interventions to mitigate antibiotic impact. Clinical trial information: NCT04875728.

Outcome of concurrent treatment with a-CTLA4 and metronidazole in murine model of colon adenocarcinoma

e14566

Background: Immune checkpoint blockade (ICB) therapy transformed clinical oncology by inducing durable responses and increasing survival rates in many types of cancers. However, ICB is effective in only in a subset of patients. Recent studies delineated the role of gut microbiome as both a biomarker and a therapeutic in ICB responsiveness. We aimed to increase understanding of the microbiome-immune system axis in ICB therapy by using antibiotics to knock out certain components of gut microbiome. Methods: We treated MC38 colon adenocarcinoma-bearing mice with a widely-used antibiotic, metronidazole, that is effective against anaerobic and protozoal infections including Clostridioides difficile – a major mediator of colitis. Metronidazole was administered via oral gavage or mixed in drinking water before and after tumor injections. Mice received twice weekly treatment with a-CTLA4 ICB. Results: Metronidazole treatment alone slowed the growth rate of MC38 tumors, consistent with the current literature regarding colon cancer murine models. When metronidazole treatment was combined with a-CTLA4 therapy, we found ̃90% complete tumor regression. In the metronidazole and a-CTLA4 combination group, we also observed an increase in the number of CD103+ type 1 conventional dendritic cells (cDC1s) in colon lamina propria, which suggests enhanced antigen sampling from lumen. Also, in the mesenteric lymph nodes (mLN), we detected upregulation of CD80 and CD86 co-stimulatory molecule expression on CX3CR1+ antigen presenting cells. Multiplex analysis of colon cytokines and colon pathology evaluation was comparable among groups, which implies a non-inflammatory environment in colon. Analysis of tumor-draining lymph nodes eight days after tumor injections showed higher expression of CD86 on CD103+ cDC1s implying superior anti-tumor immunity. 16S rRNA gene sequencing analysis of fecal samples revealed loss of Lachnospiraceae and enrichment of Bifidobacteriaceae and Sutterellaceae families in metronidazole-treated mice. Conclusions: Shifting microbiome composition with metronidazole treatment elicits a favorable anti-tumor immune response to a-CTLA4 treatment in murine colon adenocarcinoma.

Neoadjuvant and adjuvant nivolumab (nivo) with anti-LAG3 antibody relatlimab (rela) for patients (pts) with resectable clinical stage III melanoma

9502

Background: Neoadjuvant therapy (NT) for pts with clinical stage III melanoma remains an active area of research interest. Recent NT trial data demonstrates that achieving a pathologic complete response (pCR) correlates with improved relapse-free (RFS) and overall survival (OS). Checkpoint inhibitor (CPI) NT with either high or low dose ipilimumab and nivolumab regimens produces a high pCR rate of 30-45% but with grade 3-4 toxicity rate of 20-90%. In metastatic melanoma (MM), the combination of nivo with rela (anti Lymphocyte Activation Gene-3 antibody) has demonstrated a favorable toxicity profile and responses in both CPI-naïve and refractory MM. We hypothesized that NT with nivo + rela will safely achieve high pCR rates and provide insights into mechanisms of response and resistance to this regimen. Methods: We conducted a multi-institutional, investigator-initiated single arm study (NCT02519322) enrolling pts with clinical stage III or oligometastatic stage IV melanoma with RECIST 1.1 measurable, surgically-resectable disease. Pts were enrolled at 2 sites and received nivo 480mg IV with rela 160mg IV on wks 1 and 5. Radiographic response (RECIST 1.1) was assessed after completion of NT; surgery was conducted at wk 9 and specimens were assessed for pathologic response per established criteria. Pts received up to 10 additional doses of nivo and rela after surgery, with scans every 3 mo to assess for recurrence. The primary study objective was determination of pCR rate. Secondary objectives included safety, radiographic response by RECIST 1.1, event-free survival (EFS), RFS, and OS analyses. Blood and tissue were collected at baseline, at day 15, day 28, and at surgery for correlative analyses. Results: A total of 30 pts (19 males, median age 60) were enrolled with clinical stage IIIB/IIIC/IIID/IV (M1a) in 18/8/2/2 pts, respectively. 29 pts underwent surgery; 1 pt developed distant metastatic disease while on NT. pCR rate was 59% and near pCR ( < 10% viable tumor) was 7% for a major pathologic response (MPR, pCR + near pCR) of 66%. 7% of pts achieved a pPR (10-50% viable tumor) and 27% pNR (≥50% viable tumor). RECIST ORR was 57%. With a median follow up of 16.2 mos, the 1 -year EFS was 90%, RFS was 93%, and OS was 95%. 1-year RFS for MPR was 100% compared to 80% for non-MPR pts (p = 0.016). There were no treatment related gr 3/4 AEs that arose during NT; 26% of pts had a gr 3/4 AE that began during adjuvant treatment. Conclusions: Neoadjuvant and adjuvant treatment with nivo and rela achieved high pCR and MPR rates with a favorable toxicity profile in the neoadjuvant and adjuvant settings. Pts with MPR had improved outcomes compared to non-MPR pts. Translational studies to discern mechanisms of response and resistance to this combination are underway. Clinical trial information: NCT02519322.

Phase II Study of TRIplet combination Nivolumab (N) with Dabrafenib (D) and Trametinib (T) (TRIDeNT) in patients (pts) with PD-1 naïve or refractory BRAF-mutated metastatic melanoma (MM) with or without active brain metastases

9520

Background: Targeted therapies (TT) & immunotherapies (IMT) have improved survival for pts with BRAF V600 mutated stage IV MM, however many pts still progress and ultimately die from their disease. Preclinical data support the rationale for combining TT and IMT, but trials evaluating triplet combinations in IMT-naïve pts have reported mixed results. Notably, pts with untreated brain metastases (BM) were excluded from prior triplet trials and have a median PFS of 5.6 months when treated with TT. Further, there remains an unmet need for effective therapies for pts after IMT failure, as retrospective studies have reported short median PFS (5 mos) for TT in this setting. We hypothesized that N in combination with DT is safe and will demonstrate clinical activity in BRAF-mutated pts naïve or refractory to PD1 therapy and in pts with BM. Methods: We conducted a single arm phase II study (NCT02910700) of NDT in pts with BRAF-mutated, unresectable stg III or stg IV MM. Prior IMT was allowed, but prior BRAF/MEKi was not. Pts with untreated BM and asymptomatic or mildly symptomatic/requiring steroids were also allowed. Pts received 3mg/kg IV Q2wks of N (later amended to 480 mg IV Q4wks), 150mg PO BID of D and 2mg PO QD of T, all starting on Day 1. The primary objective was to determine safety and efficacy (ORR by RECIST 1.1). Monitoring for safety and futility using Bayesian stopping rules was performed. Longitudinal tissue and blood samples were collected to perform correlative analyses. Results: Following a 6 pt safety run-in with no observed DLTs, 27 pts were treated w NDT. 17 pts were PD1 refractory, 10 were PD-1 naïve. 10 of these 27 pts had a history or presence of BM, including active BM. Median follow up was 18.4 months (range 3.2-45.9). ORR in 26 evaluable pts was 92% (3 CR, 21 PR). Among the PD1 refractory pts evaluable for response (n = 16), ORR was 88% (2 CRs, 12 PR). All 10 evaluable PD-1 naïve pts achieved a response. 4 of 7 evaluable pts w BM achieved an intracranial response (57%), including 2 CRs. The median PFS for all pts was 8.5mos (8.5mos in PD1 naïve pts, 8.2mos in PD1 refractory pts). Median PFS for pts without BM was 8.5mos, 8.0 mos for those with BM. Median OS for all pts was not reached, and no statistically significantly difference in OS by PD1 exposure or presence of BM. 78% of pts experienced treatment related grade 3/4 AEs and 6 pts (22%) discontinued all 3 drugs due to toxicities. Conclusions: NDT at full doses of all 3 agents has a toxicity profile consistent with previously reported triplet combinations and shows promising clinical activity in pts with IMT refractory disease and with BM. There were no significant differences in outcomes between pts with and without BM. Translational studies to delineate predictors and mechanisms of response and resistance are ongoing. Clinical trial information: NCT02910700.

Histopathological features of complete pathological response predict recurrence-free survival following neoadjuvant targeted therapy for metastatic melanoma

BACKGROUND

Recent clinical trials demonstrated the safety and efficacy of neoadjuvant dabrafenib and trametinib (DT) among patients with surgically resectable clinical stage III BRAFV600E/K mutant melanoma. Although patients achieving a complete pathological response (pCR) exhibited superior recurrence-free survival (RFS) versus those who did not, 30% of pCR patients relapsed. We sought to identify whether histopathological features of the pathological response further delineated risk of relapse.

METHODS

Surgical resection specimens from DT-treated patients in two phase 2 clinical trials were reviewed. Histopathological features, including relative amounts of viable tumour, necrosis, melanosis, and fibrosis (hyalinized or immature/proliferative) were assessed for associations with patient outcomes.

RESULTS

Fifty-nine patients underwent surgical resection following neoadjuvant DT. Patients achieving pCR (49%) had longer RFS compared with patients who did not (P = 0.005). Patients whose treated tumour showed any hyalinized fibrosis had longer RFS versus those without (P = 0.014), whereas necrosis (P = 0.012) and/or immature/proliferative fibrosis (P = 0.026) correlated with shorter RFS. Multivariable analyses showed absence of pCR or presence of immature fibrosis independently predicted shorter RFS. Among pCR patients, mature/hyalinized-type fibrosis correlated with improved RFS (P = 0.035).

CONCLUSIONS

The extent and composition of the pathological response following neoadjuvant DT in BRAFV600E/K mutant melanoma correlates with RFS, including pCR patients. These findings support the need for detailed histological analysis of specimens collected after neoadjuvant therapy.

Radiomic signatures to predict response to targeted therapy and immune checkpoint blockade in melanoma patients (pts) on neoadjuvant therapy

10067

Background: Metastatic melanoma pt outcomes have been revolutionized by targeted therapy (TT) and immune checkpoint blockade (ICB), which are now being evaluated in the neoadjuvant (neoadj) setting. While tumor-based biomarkers may help predict response, predictors of response obtained by less invasive strategies could greatly benefit pt care and allow real-time treatment response monitoring. Radiomic signatures derived from computerized tomography (CT) images have recently been shown to predict response to ICB in stage IV pts. However, the association of radiomic features with pathological response following neoadj therapy has not been assessed. We sought to determine if radiomic assessment predicts pCR in pts receiving neoadj TT and ICB. Methods: We collected data for a cohort of melanoma pts with locoregional metastases who were treated with neoadj TT (n = 33) or ICB (n = 30). Pts received systemic therapy for 8-10 weeks prior to planned surgical resection. Responses were evaluated radiographically (RECIST 1.1) and via pathological assessment (evaluating for pathologic complete response; (pCR) versus < pCR). Thirty two pts (19 ICB; 13 TT) were included in the radiomics analysis based on the availability of appropriate CT imaging. A total of 310 unique radiomic features (10 histogram-based and 300 second-order texture features) were calculated from each extracted volume of interest (VOI). Feature extraction was performed on baseline and initial on-treatment pre-operative CT scans. Features associated with pCR were assessed using a feature selection approach based on Least Absolute Shrinkage and Selection Operator (LASSO). Selected features were used to build a classification model for prediction of pCR to ICB or TT. Leave-One-Out Cross-Validation was performed to evaluate the robustness of the estimates. Results: Out of 310 radiomic features, three features measured at baseline were able to predict a pCR to neoadj ICB or TT with sensitivity, specificity and accuracy of 100%, though these signatures were non-overlapping. In the on-treatment pre-operative scans, 3 distinct features (also non-overlapping and distinct from the predictive pre-treatment signatures) also predicted pCR to ICB and TT with 100% sensitivity, specificity and accuracy. Conclusions: Radiomic signatures in baseline and on-treatment CT scans accurately predict pCR in melanoma pts with locoregional metastases treated with neoadj TT or ICB. These provocative findings warrant further investigation in larger, independent cohorts.

Preliminary results of a phase II study of neoadjuvant checkpoint blockade for surgically resectable undifferentiated pleomorphic sarcoma (UPS) and dedifferentiated liposarcoma (DDLPS)

11505

Background: is a randomized, phase II non-comparative trial evaluating the efficacy of neoadjuvant checkpoint blockade [nivolumab (N) or ipilimumab/ nivolumab (I/N)] in patients (pts) with surgically resectable retroperitoneal DDLPS or extremity/truncal UPS treated with concurrent neoadjuvant radiation therapy (RT, UPS only). Methods: Primary endpoint was pathologic (path) response. Secondary endpoints were safety, RECIST response, recurrence-free survival, overall survival and patient-reported outcomes. Biospecimens (tumor, blood, fecal microbiome) at baseline, on therapy, and at time of surgery were collected and will be assessed for immune-based prognostic biomarkers. We assessed correlation between radiographic and pathologic response by linear regression. Correlative analyses includes assessment of tumor PD-L1 expression, characterization of tumor immune infiltrates by multiplex immunohistochemistry, and transcriptomic and genomic analyses. Results: Of the 25 pts enrolled; 24 are evaluable for response (14 DDLPS, 9 UPS). Clinical activity was variable by histologic subtype and treatment with RT. Median path response in the UPS cohort was 95% [95% CI 85–99] and was similar between the N/RT and I/N/RT groups (Table). Median path response in the DDLPS cohort was 22.5% [95% CI 85–99; Table]. Median change in tumor size (radiographic response) was -4% and +9% in the UPS and DDLPS cohorts, respectively. There was no correlation between path response and radiographic response (R2 0.0309; p = 0.43). Of 8 pts with path response ≥ 85%, there was 1 partial response, 5 stable disease and 2 progressive disease by RECIST criteria. There was 1 delay to surgery due to grade 3 hyperbilirubinemia (Arm B). There was no difference in toxicity between N/RT and I/N/RT. Conclusions: N/RT and I/N/RT have significant clinical activity in UPS; more than expected compared to historic controls. Toxicity profiles were as expected and the majority of patients underwent resection without delay. Larger studies evaluating N/RT in UPS are warranted given the significant path response in this cohort. RECIST was not associated with path response and better markers of on-treatment clinical activity are needed. Correlative analyses that may guide combination strategies are ongoing and will be presented at the meeting. Clinical trial information: NCT03307616 .

Gut microbiome diversity as an independent predictor of survival in cervical cancer patients receiving chemoradiation

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Background: Diversity of the gut microbiome is associated with response rates for patients receiving immunotherapy. Studies investigating the gut microbiome and outcomes in cancer patients often do not adjust for confounding patient and tumor characteristics. We sought to identify independent gut microbial risk factors in cervical cancer (CC) patients receiving chemoradiation (CRT) and to evaluate their impact on survival. Methods: We analyzed baseline 16S rDNA fecal microbiomes of CC patients receiving standard CRT. Patient and tumor characteristics were analyzed by univariate and multivariate Cox regression models for Recurrence-free survival (RFS) and Overall survival (OS) based on univariate p-value>0.2. Characteristics included age, body mass index (BMI), race, stage, grade, histology, nodal status, and max tumor size. Alpha (within sample) diversity was evaluated using Shannon diversity index (SDI). Kaplan-Meier curves were generated for patients with normal BMI and overweight/obese BMI based on Cox analysis. Results: 55 CC patients were included. Univariate analysis identified older age (Hazard Ratio (HR) of 0.93 (95% CI = 0.87-0.98, p = 0.0096)), SDI (HR of 0.51 (95% CI = 0.23-1.1, p = 0.087)) and BMI (HR of 0.92 (95% CI = 0.84-1, p = 0.096)) as risk factors for RFS. Multivariate survival analyses identified BMI and SDI as independent prognostic factors for RFS with a HR of 0.87 (95% CI = 0.77-0.98, p = 0.02) and 0.36 (95% CI = 0.15-0.84, p = 0.018) respectively. For OS, multivariate survival analyses again identified BMI and SDI as independent prognostic factors with a HR of 0.78 (95% CI = 0.623-0.97, p = 0.025) and 0.19 (95% CI = 0.043-0.83, p = 0.028) respectively. Conclusions: Gut diversity is a significant factor for predicting OS in CC patients undergoing CRT when BMI is accounted for, and may help explain the “obesity paradox” in cancer response. Studies exploring the relationship between gut diversity, CRT, and treatment efficacy are needed to further understand the role of the gut microbiome in treatment outcomes. [Table: see text]

Efficacy of immune checkpoint inhibitors for the treatment of metastatic melanoma (MM) in patients with concurrent chronic lymphocytic leukemia (CLL)

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Background: Patients with CLL have immune impairment with abnormalities in T-cell subset composition and immune synapse formation. The impact of these defects on response to immune checkpoint inhibitors (CPI) is not known. Given the high incidence of melanoma in patients with CLL we sought to evaluate the response to CPI in patients with concomitant MM and CLL. Methods: Retrospective analysis of 24 patients (pts) with concurrent CLL and MM who received a total of 38 CPI therapies between July 1997 and July 2019. Primary objective was to determine objective response rate (ORR), defined as complete response (CR) or partial response (PR) by RECIST1.1. Secondary outcomes included event-free survival; overall survival (OS), and duration of response (DOR). Results: The median age at CLL and melanoma diagnosis was 62 and 63 years, respectively. 71% of patients were male. Most presented with early stage CLL at diagnosis (67%), 60% had mutated IGVH, and 47% had deletion of 13q by FISH. 71% remained on observation for their CLL. Median time from melanoma diagnosis to CPI initiation was 13.5 months. 83% had stage IV MM and 17% stage III MM at the time of therapy. 17% had increased LDH. The most common melanoma mutations were BRAF(35%), BRAFV600 (26%), TP53 (30%) and NRAS (26%). Median follow up was 37 months and the ORR was 24% (Table). Median DOR was 41 months and median OS is 26.4 months. Immune-mediated adverse events occurred in 42%, including 13% fever, 11% thrombotic events, 8% endocrine dysfunction. 13 pts are alive and 11 pts died (8 pts due to MM progression). There were no significant changes in absolute lymphocyte counts during CPI therapy. 2 pts received CPI while on ibrutinib or ibrutinib+venetoclax therapy with ongoing CLL responses. Conclusions: Our experience indicates that CPIs can be effective for the treatment of MM in patients with concurrent CLL, achieving durable responses. Immuno-mediated toxicities were frequently observed. A lower ORR was observed in first-line CPI in MM, however the numbers of pts are small. Further studies are needed to determine if initial or concurrent treatment for CLL could improve CPI outcomes and survival. Additional studies evaluating T cells function and tissue infiltration in these patients are ongoing. [Table: see text]

Investigating the tumor immune infiltrate for populations that predict immune-related adverse events (irAEs) in patients receiving PD-1 inhibitors

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Background: The mechanistic relationship between clinical benefit and immune-related adverse events (irAEs) in response to immune checkpoint inhibitors (ICIs) remains unclear, with several clinical studies reporting that irAEs are biomarkers of responses. Single-cell RNA sequencing (scRNAseq) analysis of tumors from patients with advanced melanoma before and after treatment with ICIs have identified immune cells that correlate with response to ICIs. We sought to evaluate if these populations were also associated with irAEs. Methods: A published scRNAseq data set generated with the Smart-Seq2 protocol (Sade-Feldman M, et al. Cell 2018.) was re-analyzed, stratified by two definitions of irAEs: (1) toxicity requiring systemic immunosuppression (prednisone > 10mg/day) or (2) systemic immunosuppression and/or endocrinopathy. Unbiased single-cell analysis was performed, followed by sub-clustering of T cell populations. The percentage of cells in each cluster was determined on a per sample basis. Results: 13,184 immune cells from 39 samples collected from 25 patients were re-analyzed. 27 samples were from patients who did not respond to ICIs, while 12 samples came from responding patients. 21 samples came from patients who required immunosuppression, 5 samples from patients with isolated thyroiditis, and 13 samples from patients who met neither irAE criteria. Unsupervised scRNAseq analyses focused on ICI efficacy re-capitulated published associations between response and populations that included B-cells (p < 0.01) and TCF7 expressing T-cells (p < 0.01). While these cell populations were not associated with either definition of toxicity, we observed a non-Treg CD4 expressing T cell population (0.8-10.5% cells/sample) that positively correlated with either definition of toxicity (p < 0.05) but not efficacy. Conclusions: In a patient cohort with advanced melanoma, tumor-infiltrating immune cell populations associated with response to ICI therapy were not associated with irAEs. This suggests that biomarkers of ICI response may not function as biomarkers of irAEs, and ongoing analysis will seek to validate this result. Understanding the differences between ICI response and irAEs may identify new therapeutic targets for maximizing efficacy while mitigating toxicity.

Immune phenotype and response to neoadjuvant systemic therapy (NAST) in triple negative breast cancer (TNBC)

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Background: In TNBC patients (pts) receiving NAST, increasing tumor infiltrating lymphocytes (TILs) is associated with higher pathologic complete response (pCR) rates. However, since the presence of TIL do not consistently predict pCR, the current study was undertaken to more fully characterize the immune cell response and its association with pCR. Methods: T cell receptor (TCR) sequencing, PD-L1 immunohistochemistry and multiplex immunofluorescence were performed on prospectively collected pre-NAST tumor samples from 98 pts with stage I-III TNBC enrolled in ARTEMIS (NCT: 02276443). TCR clonality was calculated using Shannon’s entropy. PD-L1+ was defined as ≥1% immune cell staining. Response to NAST was defined using the residual cancer burden (RCB) index. Associations between TCR clonality, immune phenotype, and response were examined with the Wilcoxon rank sum test, Spearman’s rank correlation and multivariable logistic regression using stepwise elimination (threshold p > 0.2), as appropriate. Results: The pCR rate was 39% (38/98). pCR was associated with higher TCR clonality (median = 0.2 [in pts with pCR] vs 0.1 [in pts with residual disease], p = 0.05). Notably, the association between pCR and higher TCR clonality was observed in pts with ≥5% TIL (n = 61; p = 0.05) but not in pts with < 5% TIL (n = 37; p = 0.87). Among pts with ≥5% TIL, TCR clonality emerged as the only independent predictor of response in a multivariable model of tumor immune characteristics (odds ratio/0.1 increase in TCR clonality: 3.0, p = 0.021). PD-L1+ status was associated with higher TCR clonality (median = 0.2 [in PD-L1+] vs 0.1 [in PD-L1-], p = 0.004). Higher TCR clonality was associated with higher CD3+ (rho = 0.32, p = 0.0018) and CD3+CD8+ (rho = 0.33, p = 0.0013) infiltration but lower expression of PD-1 on CD3+ (rho = -0.24, p = 0.021) and CD3+CD8+ cells (rho = -0.21, p = 0.037). Conclusions: In TNBC, a more clonal T cell population is associated with an immunologically active microenvironment (higher CD3+ and CD3/8+ T cell; lower PD-1+CD3+ and PD-1+CD3/8+ T cell; PD-L1+) and favorable response to NAST, especially in pts with ≥5% TIL, suggesting a role for deep immune phenotyping in further refining the predictive value of TILs.

Pathological assessment of resection specimens after neoadjuvant therapy for metastatic melanoma

Background

Clinical trials have recently evaluated safety and efficacy of neoadjuvant therapy among patients with surgically resectable regional melanoma metastases. To capture informative prognostic data connected to pathological response in such trials, it is critical to standardize pathologic assessment and reporting of tumor response after this treatment.

Methods

The International Neoadjuvant Melanoma Consortium meetings in 2016 and 2017 assembled pathologists from academic centers to develop consensus guidelines for pathologic examination and reporting of surgical specimens from AJCC (8th edition) stage IIIB/C/D or oligometastatic stage IV melanoma patients treated with neoadjuvant-targeted or immune therapy. Patterns of pathologic response are provided context to inform these guidelines.

Results

Based on our collective experience and guided by efforts in well-established neoadjuvant settings like breast cancer, procedures directing handling of pre- and post-neoadjuvant therapy-treated melanoma specimens are provided to facilitate comparison of findings across different trials and centers. Definitions of pathologic response are provided together with guidelines for reporting and quantifying the extent of pathologic response. Finally, the spectrum of histopathologic responses observed following neoadjuvant-targeted and immune-checkpoint therapy is described and illustrated.

Conclusions

Standardizing pathologic evaluation of resected melanoma metastases following neoadjuvant-targeted or immune-checkpoint therapy allows more robust stratification of patient outcomes. This includes recognizing the spectrum of histopathologic response patterns to neoadjuvant therapy and a standard approach to grading pathologic responses. Such an approach will facilitate comparison of results across clinical trials and inform ongoing correlative studies into the mechanisms of response and resistance to agents applied in the neoadjuvant setting.

Lymphodepletion (LD), tumor-infiltrating lymphocytes (TIL) and high (HD-IL2) versus low-dose (LD-IL2) IL-2 followed by pembrolizumab (pembro) in patients (pts) with metastatic melanoma (MM)

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Background: TIL adoptive cell transfer (ACT) therapy can produce durable responses for MM pts although efficacy appears lower in the era of checkpoint inhibitors. Toxicities from HD-IL2, including sepsis physiology, limits widespread use of this regimen. Suppression of transferred TIL by either tumor cells or the tumor microenvironment could limit TIL responses. Pembro is known to promote T cell activation, thus, we evaluated the efficacy and safety of TIL with pembro with HD-IL2 versus LD-IL2. Methods: Pts with MM who had tumor harvested and cryopreserved TIL at MD Anderson with PS 0-1 and normal organ function were eligible. All pts received a standard LD regimen consisting of cyclophosphamide and fludarabine, followed by infusion of pooled ex-vivo expanded TIL and either HD-IL2 (Arm 1: 720,000 IU/kg IV q 8 hrs up to 15 doses) or LD-IL2 (Arm 2: 2 million IU SC for 14 d). Pts received pembro 200mg IV starting 21 d post T cell infusion every 3 wks for up to 2 yrs. Pts were randomized 1:1 based on stage and LDH. Paired blood and tumor biopsies were obtained prior to LD, prior to first and second dose of pembro and at time of progression. Results: A total of 36 pts were planned to enroll (18 in each arm); however, the protocol met pre-specified futility boundaries in Arm 1 which prompted early closure after treatment of 14 pts (7 in each Arm). Median age was 50 yrs, 6 were female, 8 had cutaneous melanoma, 2 mucosal, 2 uveal and 2 unknown primary. 86% were stage M1c, 14% M1D, 50% had LDH elevation. Median lines of prior therapy were 3 (range 1-6), including prior anti PD-1 in 13 pts. Best overall response was 1 PR (for 10 mos), 2 SD, 3 PD, 1 NE in Arm 1; 1 PR (ongoing over 36 mos), 1 SD, 5 PD in Arm 2. With median follow up of 9.2 mos, PFS was 3.9 mos for Arm 1 and 2.1 mos for Arm 2 (p = 0.99). Median OS was 9.7 mos for Arm 1 and 8.8 mos for Arm 2 (p = 0.71). Toxicity was similar in both Arms but with lower rates of grade 3 febrile neutropenia (57% vs. 71%) and shorter hospital stay (median 16 vs. 18 d) in Arm 2 vs. Arm 1. Conclusions: In a heavily treated pt population, TIL with pembro achieved low response rates. Use of LD-IL2 did not diminish efficacy and may be better tolerated than HD-IL2 for TIL ACT. Correlative studies are ongoing to determine mechanisms of treatment response and failure. Clinical trial information: NCT02500576.

Pathological response and survival with neoadjuvant therapy in melanoma: A pooled analysis from the International Neoadjuvant Melanoma Consortium (INMC)

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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.

A phase II study of oral azacitidine (CC-486) in combination with pembrolizumab (PEMBRO) in patients (pts) with metastatic melanoma (MM)

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Background: Immune checkpoint blockade (ICB) have improved survival for many pts with MM, offering durable responses in up to 35% of pts, but many have short-lived or no response ( > 40%). A potential immune escape mechanism is the subversion of cellular epigenetic machinery to impact multiple aspects of the immune response such as suppression of Cancer Testis Antigen (CTA), which can be reversed in preclinical models by DNA hypomethylating agents (HMA), thereby increasing cancer cell immunogenicity. HMAs can also increase T cell infiltration and T cell-mediated tumor killing, and they achieve synergy with CBI in preclinical models. This suggests that epigenetic therapy with CBI is a rational combination to target MM. We hypothesize that CC-486 (an oral HMA) + PEMBRO will be tolerated at biologically relevant doses and enhance response to PEMBRO in pts with MM who are PD-1 naïve and reverse resistance to (ICB) in pts refractory/resistant to PD-1. Methods: This study (NCT02816021) evaluated the safety and efficacy of CC-486 (300 mg PO QD on days 1-14/21 day cycle) + PEMBRO (200mg IV Q 21 days) defined by Objective Response Rate (ORR) by RECIST 1.1 in pts with MM. PD-1 naïve pts were assigned to Arm A and pts with progression on prior PD-1 therapy to Arm B. Unlimited prior systemic therapies were allowed on Arm B. Continuous monitoring for toxicity and futility was performed and assumes an ORR of > 35% (Arm A) and > 15% (Arm B) at 95% power. Tumor biopsies at baseline and post treatment were mandated. Results: 22pts, 11 in each arm, have been treated. The most common AEs were nausea, vomiting, diarrhea, fatigue, and anemia. The most common gr 3/4 toxicities were neutropenia (3), diarrhea (2), dehydration (2), and rectal hemorrhage (1). 5 of 9 evaluable pts in Arm A achieved a PR (55% ORR); 0 of 9 evaluable pts in Arm B pts have responded. Conclusions: Although this regimen was tolerated in both arms, Arm B met futility stopping rules and was closed. The initial response rate in Aim A (55%) is promising, and accrual to this Arm continues. Analyses of longitudinally collected tumor biopsies are underway to interrogate the effects of HMA on the immune response to both arms. Clinical trial information: NCT02816021.

Spitzoid melanoma with histopathological features of ALK gene rearrangement exhibiting ALK copy number gain: a novel mechanism of ALK activation in spitzoid neoplasia

Spitzoid neoplasms pose diagnostic difficulties because their morphology is not consistently predictive of their biological potential. Recent advances in the molecular characterization of these tumours provides a framework by which they can now begin to be categorized. In particular, spitzoid lesions with ALK rearrangement have been specifically associated with a characteristic plexiform growth pattern of intersecting fascicles of amelanotic spindled melanocytes. We report the case of an 87-year-old man with a 3-cm nodule on his mid-upper back comprised of an intradermal proliferation of fusiform amelanotic melanocytes arranged in intersecting fascicles with occasional peritumoral clefts. Immunohistochemical studies demonstrated diffuse, strong expression of SOX10 and S100 by the tumour cells and diffuse, weak-to-moderate cytoplasmic positivity for anaplastic lymphoma kinase (ALK), suggestive of ALK rearrangement. Fluorescence in situ hybridization revealed no ALK rearrangements but instead revealed at least three intact ALK signals in 36% of the tumour cells, confirming ALK copy number gain. To our knowledge, this is the first reported case of a plexiform spitzoid neoplasm exhibiting ALK copy number gain instead of ALK rearrangement. This case suggests that ALK copy number gain is a novel mechanism of ALK activation but with the same characteristic histopathological growth pattern seen among ALK-rearranged spitzoid neoplasms.

Abstract P3-05-08: Lymphoid and myeloid cell characterization of inflammatory breast cancer tumor microenvironment and correlation to pathological complete response

Background: Inflammatory breast cancer (IBC) is an aggressive form of breast cancer with poor response rates to current chemotherapy regimens. With recent successes of immune targeted therapies in other solid tumors and a growing understanding of how the immune tumor microenvironment (TME) affects non-IBC outcomes, we sought to characterize the immune TME in IBC to identify biomarkers of treatment response and potential targets for drug development.

Methods: Pre-treatment core biopsy samples were identified from the MD Anderson Cancer Center IBC tissue bank from patients with stage III and de novo stage IV (with T4d) disease who received neoadjuvant chemotherapy (NAC) with intent to take to mastectomy. Lymphocytes were characterized by stromal tumor infiltrating lymphocyte (sTIL) quantification, CD8 T cell quantification, and T cell receptor sequencing. PD-L1 expression was assessed using DAKO 22C3 clone on tumor and immune cells. Myeloid cells were characterized using a multiplex immunohistochemistry approach, using CD68 and CD163 for macrophage markers, tryptase for mast cell marker, HLA-DR for class II antigen presentation marker, and cytokeratin as tumor marker. Spatial analyses were performed by determining probabilities of finding cell 1 of interest within 20 uM of cell 2 of interest and computing area under the curve for statistical comparison.

Results: 91 patients with stage III (N=62) or de novo stage IV (n=29) disease were identified. Breast cancer subtype included 25 triple negative, 34 HER2+ and 32 HER2-HR+. 86 patients received a mastectomy, of whom 33 (38.4%) patients experienced a pathologic complete response (pCR). sTIL was higher in stage III tumors (11.9 vs 4.8%, p&lt;0.001) and in those having a pCR (13.8 vs 7.3%, p=0.019). CD8 T cell density (available in 48 cases) similarly was higher in stage III patients (360.3 vs 178.8 counts/mm2, p=0.040) and pCR cases (452.3 vs 219.2 counts/mm2, p=0.080) but also higher in HER2+ disease (560.9 for HER2+ vs 239.9 counts/mm2, p=0.087 for TNBC and 153.6 counts/mm2, p=0.005 for HER2-HR+). T cell clonality (available in 32 cases) ranged from 0.004 to 0.242 but showed no correlation to tumor characteristics or response. PD-L1 complete tumor membranous expression was seen in only 1 of 47 cases, whereas PD-L1 positivity on immune cells was seen on 36.2% of cases; neither correlated to response. Myeloid cell assessment (available in 25 cases) showed higher mast cell infiltration in non-pCR cases (63.8 vs 26.8 counts/mm2, p=0.008) and spatial analysis (performed on 10 cases) identified that closer proximity of mast cells to CD8 T cells correlates with response (AUC 6.0 vs 2.2, p=0.017), suggesting a possible immunosuppressive mechanism. HLA-DR analysis demonstrated no difference by response as a single stain marker, but co-localization of HLA-DR with cell type shows higher HLA-DR expression on tumor cells in non-responders (14.6 vs 1.6%, p=0.031).

Conclusions: Higher TIL and CD8 T cell density are correlated with improved responses to NAC in IBC. Mast cell infiltration and HLA-DR expression on tumor cells are inversely correlated to response and suggest possible mechanisms of resistance. Mast cells could present potential therapeutic target in IBC.

Citation Format: Reddy SM, Reuben A, Jiang H, Roszik J, Tetzlaff MT, Reuben J, Wang L, Tsujikawa T, Barua S, Rao A, Villareal L, Wood A, Woodward W, Ueno NT, Krishnamurthy S, Wargo JA, Mittendorf EA. Lymphoid and myeloid cell characterization of inflammatory breast cancer tumor microenvironment and correlation to pathological complete response [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-05-08.

Gut microbiome modulates response to anti-PD-1 immunotherapy in melanoma patients

Preclinical mouse models suggest that the gut microbiome modulates tumor response to checkpoint blockade immunotherapy; however, this has not been well-characterized in human cancer patients. Here we examined the oral and gut microbiome of melanoma patients undergoing anti-programmed cell death 1 protein (PD-1) immunotherapy (n = 112). Significant differences were observed in the diversity and composition of the patient gut microbiome of responders versus nonresponders. Analysis of patient fecal microbiome samples (n = 43, 30 responders, 13 nonresponders) showed significantly higher alpha diversity (P < 0.01) and relative abundance of bacteria of the Ruminococcaceae family (P < 0.01) in responding patients. Metagenomic studies revealed functional differences in gut bacteria in responders, including enrichment of anabolic pathways. Immune profiling suggested enhanced systemic and antitumor immunity in responding patients with a favorable gut microbiome as well as in germ-free mice receiving fecal transplants from responding patients. Together, these data have important implications for the treatment of melanoma patients with immune checkpoint inhibitors.

Cancer Evolution during Immunotherapy

Immune checkpoint blockade has revolutionized cancer treatment. In this issue of Cell, insights from a longitudinal multi-omics analysis of the largest yet-reported cohort of melanoma patients reveal how tumor and immunity co-evolve during anti-PD-1 therapy.

Relapse-free survial and target identification to enhance response with neoadjuvant and adjuvant dabrafenib + trametinib (D+T) treatment compared to standard-of-care (SOC) surgery in patients (pts) with high-risk resectable BRAF-mutant metastatic melanoma

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Background: Targeted and immune therapies have dramatically improved outcomes in stage IV metastatic melanoma pts. These agents are now being tested in earlier-stage disease. SOC surgery for high-risk resectable melanoma (AJCC stage IIIB/IIIC), with or without adjuvant therapy, is associated with a high risk of relapse (~70%). We hypothesized that neoadjuvant (neo) + adjuvant treatment with D+T improves RFS in these pts. Longitudinally collected biospecimens from pts receiving this treatment were analyzed to identify candidate strategies to further improve outcomes. Methods: A prospective single-institution randomized clinical trial (NCT02231775) was conducted in BRAF-mutant pts with resectable Stage IIIB/C or oligometastatic stage IV melanoma. Pts were randomized 1:2 to SOC (Arm A) versus neo + adjuvant D+T (Arm B; 8 wks neo + 44 wks adjuvant). The primary endpoint was RFS. Tumor biopsies were collected at baseline, week 3, and at surgery for molecular and immune profiling (whole exome sequencing, gene expression profiling, IHC, flow cytometry). Results: 21 of a planned 84 patients were enrolled (Arm A = 7, Arm B = 14). Arms were well balanced for standard prognostic factors, and toxicity was manageable. RECIST response rate with neo D+T was 77%, and the pathologic complete response rate (pCR) was 58%. First interim analysis revealed significantly improved RFS in the D+T arm over SOC (HR 62.5, p < 0.0001), leading to early closure to enrollment. Pts with a pCR at surgery had significantly improved RFS versus pts without pCR (p = 0.04) on neo D+T. Tumor profiling revealed incomplete MAPK pathway blockade and higher levels of CD8+ T cells expressing immunomodulators Tim-3 and Lag-3 in pts who did not achieve a pCR. Conclusions: Neo + adjuvant D+T is associated with a high pCR rate and markedly improved RFS over SOC in pts with high-risk resectable BRAF-mutant metastatic melanoma. pCR at surgery is associated with improved RFS. Tumor analyses reveal candidate targets for testing in future trials to enhance responses to neo D+T. Clinical trial information: NCT02231775.

Immune and molecular determinants of response to neoadjuvant chemotherapy in inflammatory breast cancer

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Background: Inflammatory breast cancer (IBC) is the most aggressive form of primary breast cancer and has poor responses to standard of care neoadjuvant chemotherapy (NAC). Given there is a limited understanding of the immune microenvironment of IBC, this study aims to characterize the immune and molecular profiles of stage III and IV IBC and to identify biomarkers of response to treatment and targets for future therapies. Methods: IBC patients with available pre-treatment tumor samples and with intent to take to mastectomy were identified in the IBC tumor registry and tissue bank. Tumor infiltrating lymphocyte (TIL) infiltration in the tumor stroma was quantified on H&E slides per consensus guidelines (n = 91). On a subset of patients with available samples, deeper immune profiling was performed, including quantification of CD8 T cells by immunohistochemistry (IHC) (n = 33), PD-L1 tumor expression by IHC (n = 14), myeloid cells by multiplex IHC (n = 15), T cell clonality by T cell receptor sequencing (n = 22), and total mutational load (TML) by whole exome sequencing (n = 20). Results: Mean TIL were higher in tumors from patients that achieved a pathological complete response (pCR) to NAC than from those that did not (13.79 vs 7.24%, p = 0.019) and in patients with stage III compared to stage IV disease (11.90 vs 4.79%, p < 0.001). Though no statistically significant differences in CD8 infiltrate by response, stage, or receptor status were seen, the presence of a more clonal T cell population was predictive of pCR (13.27 vs 5.70% top 5 clone frequency, p = 0.042 among stage III patients). Myeloid cell staining revealed that tryptase staining, indicative of mast cells, was inversely associated with pCR (28.26 vs 108.0 counts/mm2, p = 0.011). Three of fourteen patient tumors displayed low PD-L1 tumor positivity (range 1-2%, 1+-2+) with the others being negative. Genomic profiling showed no statistically significant differences in TML by stage, receptor status, response, or immune infiltrate. Conclusions: Higher TIL, more clonal T cells, and lower mast cell infiltration are predictive of response to NAC in IBC. Comprehensive immune characterization of a larger cohort of pre- and post-treatment samples is currently underway.

A toll-like receptor agonist to drive melanoma regression as a vaccination adjuvant or by direct tumor application

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Background: Toll like receptor (TLR) agonists may enhance vaccination or direct immune activation at the tumor microenvironment. This trial evaluates the biologic and clinical effects of Resiquimod, a TLR 7/8 agonist that can activate both myeloid (mDC, TLR 8) and plasmacytoid (pDC, TLR 7) dendritic cells, in patients with advanced stage melanoma. Methods: Class I HLA-A0201+ subjects with in-transit melanoma metastases or high risk for recurrence were vaccinated weekly with peptide vaccination (class I restricted peptide GP100209-2m and, if HLA-DP4+, also with class II restricted peptide MAGE-3243-258). Subjects were randomized 1:1 to receive Resiquimod as an adjuvant applied to the GP100 vaccination site. Subjects with in-transit disease were thereafter treated with resiquimod topically on half of the target lesions. Results: All patients (n = 47) underwent GP100209-2m vaccination, a majority (39) also received the MAGE-3243-258 peptide. The type I interferon-inducible genes (Mx A and IRF7), IFNg, and IP-10 RNA expression were up-regulated only in vaccination sites treated with Resiquimod (each p < 0.01) , demonstrating pDC activation (Type I interferon) and possibly T and NK cell activation (IFNg and IP-10). Nineteen subjects had in-transit disease at entry into the trial. In response to peptide vaccination alone, tumor regression was more likely in patients who received Resiquimod at the vaccination site (group A) compared to those who did not (group B). (4/9 vs 0/10, p = 0.033). In group A, 5 patients continued treatment with Resiquimod topically on the tumors, and all had tumor response (4PR, 1CR). In group B, 5 continued to tumoral resiquimod and 3 had regression (3 PR). Conclusions: Resiquimod increases Type I interferon and IFNg at the peptide vaccination site by activation of pDC/mDC and increases the antitumor response sufficiently to mediate regression of in-transit melanoma metastasis. Resiquimod on in-transit melanoma, in vaccinated hosts, drives regression of metastases, regardless of previous exposure at vaccination. Clinical trial information: NCT00960752.

Investigation of mechanisms of resistance to ipilimumab therapy with a pre-surgical trial in patients with high-risk, localized prostate cancer

5081

Background: Anti-CTLA-4 therapy ipilimumab (BMS) has led to clinical benefit in patients with metastatic melanoma. However, in multiple clinical trials in patients with prostate cancer, ipilimumab has not demonstrated significant clinical benefit. To identify potential immune inhibitory pathways responsible for resistance to ipilimumab therapy, we evaluated tumor samples from a pre-surgical clinical trial and performed correlative laboratory studies. Methods: We carried out a pre-surgical clinical trial with androgen deprivation therapy (ADT), (leuprolide acetate, Tap Pharmaceuticals) plus ipilimumab in patients with localized, high-risk prostate cancer. Each patient received one injection of leuprolide (22.5 mg) on week 0 and ipilimumab (10 mg/kg) on weeks 1 and 4. Patients then underwent surgery at week 8. Tumor tissues were collected at baseline and then at surgery for flow cytometry, IHC, multiplex immunofluorescence, and gene profiling analyses. In vitro studies were carried out for functional analysis. Results: Sixteen patients completed treatment with ipilimumab plus ADT and surgery. We observed a significant increase of immune cells including T cells and macrophages into prostate tumors after ipilimumab therapy, similar to data observed in ipilimumab-treated melanoma samples. However, compared to melanoma tumors, we found higher expression of PD-L1 and VISTA inhibitory molecules on CD68+ macrophages in prostate tumors. Interestingly, PD-L1 and VISTA were expressed on distinct subset of CD68+ macrophages, with high expression of CD163, suggesting an M2 subtype. In vitro studies demonstrated that engagement of PD-L1 and/or VISTA pathways inhibited T cell responses. Co-culture with monocytes resulted in suppression of T cell function, which can be reversed with anti-VISTA blocking antibody. Conclusions: These data suggest that evolving compensatory inhibitory pathways including PD-L1 and VISTA may mediate resistance of prostate cancer to ipilimumab therapy. Concurrent blockade of other immune checkpoints such as PD1/PD-L1 and/or VISTA may be necessary to provide significant clinical benefits for patients with prostate cancer. Clinical trial information: NCT01194271.

Multidimensional spatial characterization of the tumor microenvironment (TME) in synchronous melanoma metastases (SMM) to yield insights into mixed responses to therapy in metastatic melanoma (MM) patients (pts)

9575

Background: Although both targeted and immune therapies have significantly improved outcomes for mm pts, only a minority of pts experience durable responses with many pts with multiple SMM demonstrating differential responses to therapy. We performed multidimensional spatial characterization of immune markers in SMM from mm patients treated with targeted and immune therapies to improve our understanding of correlations and determinants of response. Methods: NanoString's Digital Spatial Profiling research platform was used on 6 SMM from 3 pts (treatment-naïve; BRAF + MEK targeted therapy treated; anti-PD-1 immunotherapy treated) for 30 immune and signaling proteins. For analysis, we selected and compared immune-rich (CD45+) and tumor-rich (S100B+) regions across SMM. Results were compared to lesion-specific clinical responses. Results: Striking differences in patterns of expression across SMM from individual pts were detected, including in Ki67, CD68 myeloid cells, and the potent immunosuppressor B7-H3. SMM progressing after targeted therapy demonstrated higher pAKT and PD-L1 expression, consistent with described resistance mechanisms. Large differences in expression of PD-L1 were noted following anti-PD-1 therapy, which could contribute to heterogeneous responses. Differential expression patterns in the TME associated with response were also detected, including in increases in CD4 and CD14 cells in progressing lesions. Conclusions: Striking differences in responding and non-responding SMM were observed, providing potential explanations for the heterogeneous clinical responses frequently observed in mm pts. Studies are ongoing to further characterize interactions and spatial distribution of cell types, as well as integrate these findings with previous molecular and immune profiling data (whole exome sequencing, gene expression profiling, flow cytometry, IHC, TCR sequencing) in these and additional SMM to identify actionable strategies to homogenize responses across metastases in mm pts.

Molecular and immune predictors of response and toxicity to combined CTLA-4 and PD-1 blockade in metastatic melanoma (MM) patients (pts)

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Background: Combined treatment with ipilimumab and nivolumab (Ipi/Nivo) achieves clinical responses in > 50% of mm pts. However, responses are not universal and toxicity may be limiting, thus biomarkers of response and toxicity are needed to optimize and personalize this therapy. Methods: Tumor biopsies were collected before (n = 29) and on treatment (n = 7) from mm pts (n = 40) treated with Ipi/Nivo. Whole exome sequencing (WES), gene expression profiling, TCR sequencing, and immunohistochemistry (IHC) were performed to define molecular and immune features of the tumors. Radiographic responses in patients were assessed via RECIST 1.1criteria, and patients were classified as responders (R) deriving clinical benefit (with SD, PR, CR) and non-responders (NR) not deriving clinical benefit (PD). Toxicity was also scored, with patients dichotomized into low toxicity ( < grade 2) versus high toxicity ( > grade 3) re: immune-related (IR) toxicities. Results: In this cohort, the response rate was 80%, with 53% of patients experiencing > grade 3 toxicity. There was no significant difference in baseline mutational load in responders (R) vs non-responders (NR) to Ipi/Nivo, but NR had a higher burden of copy number alterations (CNA; p = 0.013), with frequent alterations detected in PTEN, JAK2, and B2M. There were no significant differences in baseline CD8+ T cell density, expression of immune-related genes, or T cell clonality for R vs NR pts. Ipi/Nivo treatment increased intratumoral T cell clonality, but this did not correlate with response. A more diverse peripheral T cell repertoire at baseline was detected in pts who developed IR toxicity (p < 0.05). Conclusions: This data suggests that responses to Ipi/Nivo in mm may occur in the absence of high mutational load or brisk immune infiltrate at baseline. Putative mechanisms of resistance to Ipi/Nivo include high burden of CNA and alterations in PTEN, JAK2, and B2M. Together these studies identify candidate biomarkers of resistance and toxicity for Ipi/Nivo, though they need to be tested in larger cohorts and across cancer types.

A phase II study of oral azacitidine (CC-486) in combination with pembrolizumab (PEMBRO) in patients with metastatic melanoma (MM)

TPS9594

Background: Immune checkpoint inhibitors have impressive response rates and improved survival for many pts with MM, offering durable responses in up to 35% of pts while others have short-lived or no response ( > 40%). A potentially targetable mechanism for immune escape is for cancers to subvert the cellular epigenetic machinery, affecting multiple aspects of the immune response from suppression of tumor antigen expression [such as Cancer Testis Antigens (CTA)] to antigen processing and presentation, thus allowing tumor proliferation to continue undetected. In preclinical models, decitabine (DAC), a DNA hypomethylating agent (HMA), has been able to revert heterogeneous CTA expression profiles, increasing cancer cell immunogenicity. HMAs also increased TH1-chemokine expression, T cell tumor infiltration, T cell-mediated tumor killing, and have been shown to be synergistic with checkpoint inhibitors in preclinical models. This suggests that epigenetic therapy with checkpoint inhibition is a rational combination to target MM. Clinical advantages of the HMA CC-486 over DAC include oral bioavailability and potential versatility in dosing and schedule. We hypothesize that CC-486 + PEMBRO will be tolerated at biologically relevant doses; enhance response to PEMBRO in pts with mm who are PD-1 naïve; and reverse resistance to immunotherapy in pts refractory/resistant to PD-1 directed therapy. Methods: This study will evaluate the safety and efficacy of CC-486 + PEMBRO defined by Objective Response Rate (ORR) by RECIST 1.1 in pts with MM. Pts who are PD-1 naïve (Arm A, n = 36) and pts who have progressed on prior PD-1 directed therapy (Arm B, n = 35) will be enrolled. Unlimited prior systemic therapies will be allowed. Pts will receive 300mg PO of CC-486 on days 1-14 and 200mg IV of PEMBRO every 3 weeks. Continuous monitoring for toxicity and futility will be performed and assumes an ORR of > 35% and > 15% for Arms A and B, respectively (95% power). Tumor biopsies at baseline and post treatment are required. Effects of CC-486 + PEMBRO on CTAs, MDSCs and Tregs, and correlation between mutation burden and response will be studied. This study is open for enrollment. Clinical trial information: NCT02816021.

Association of the diversity and composition of the gut microbiome with responses and survival (PFS) in metastatic melanoma (MM) patients (pts) on anti-PD-1 therapy

3008

Background: Significant advances have been made in cancer therapy with immune checkpoint blockade. However, responses in pts with MM are variable, and insights are needed to identify biomarkers of response and strategies to overcome resistance. There is a growing appreciation of the role of the microbiome in cancer, and evidence in murine models that modulation of the gut microbiome may enhance responses to immune checkpoint blockade, though this has not been well studied in pts. Thus we evaluated the microbiome in a large cohort of pts with MM, focusing on responses to anti-PD-1. Methods: We collected oral (n = 234) and gut microbiome samples (n = 120) on a large cohort of of MM patients (n = 221). Of note, the majority of pts were treated with PD-1 based therapy (n = 105). Pts on anti-PD1 were classified as either responders (R) or non-responders (NR) based on RECIST criteria, and 16S rRNA and whole genome shotgun (WGS) sequencing were performed. Immune profiling (via immunohistochemistry, flow cytometry, cytokines and gene expression profiling) was also done in available pre-treatment tumors at baseline. Results: Significant differences in diversity and composition of the gut microbiome were noted in R vs NR to anti-PD-1, with a higher diversity of bacteria in R vs NR (p = 0.03). Differences were also noted in the composition of gut bacteria, with a higher abundance of Clostridiales in R and of Bacteroidales in NR. Immune profiling demonstrated increased tumor immune infiltrates in R pts , with a higher density of CD8+T cells; this correlated with abundance of specific bacteria enriched in the gut microbiome (r = 0.59, 0.014). Other features of enhanced immunity were also noted, and WGS revealed differential metabolic signatures in R vs NR. Furthermore, diversity (p = 0.009; HR = 7.67) and abundance of specific bacteria in R (p = 0.007; HR = 3.88) was associated with improved PFS to anti-PD-1 therapy. Conclusions: Diversity and composition of the gut microbiome differ in R vs NR pts with MM receiving anti-PD-1 therapy. These have potentially far-reaching implications, though results need to be validated in larger cohorts across cancer types.

Preliminary results from the international neoadjuvant melanoma consortium (INMC)

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Background: For several cancers, response to neoadjuvant therapy (NAT) correlates with survival. Targeted and immune therapies achieve high response rates and durable survival in many patients with metastatic melanoma. Their role as NAT for stage III disease is not clear, and whether pathological response following NAT correlates with relapse-free (RFS) or overall survival (OS) in melanoma is unknown. Methods: Pooled clinical data from four ongoing NAT clinical trials (NCT02437279, NCT02231775, NCT02519322, NCT01972347) at three large melanoma centers participating in the INMC were examined. All trials included only patients with surgically resectable clinical stage III melanoma. NAT regimens included dabrafenib/trametinib (DT) and nivolumab (nivo) [single agent or in combination with ipilimumab (ipi/nivo)]. Patients who had undergone surgery prior to 27th January 2017 are included in this preliminary analysis. A pathological complete response (pCR) was defined as no viable melanoma cells in the resected specimen by hematoxylin and eosin evaluations by dedicated dermatopathologists. Results: 58 patients with clinical stage III melanoma (AJCCv7: 18 IIIB, 40 IIIC) have completed NAT and undergone surgery. 18 received neoadjuvant immunotherapy (IT): ipi/nivo x2 doses (N = 10), ipi/nivo x3 doses (N = 4) or nivo x4 doses (N = 4). 40 received neoadjuvant DT, either for two (N = 10) or three months (N = 30). Median age is 55 years (range 22-84). A pCR was observed in 50% of patients, 7 (39%) with IT and 22 (55%) with DT. Median follow-up is 10.2 months (95% CI 8.7-12.5). 14 (24%) patients have recurred (5 local, 8 distant, 1 both), 2 (11%) after IT, 12 (30%) after DT. For those with pCR, 14% have recurred, 0/7 (0%) after IT, 4/22 (18%) after DT. In contrast, for those without pCR, 34% have recurred, 2/11 (18%) after IT and 8/18 (44%) after DT. Two deaths have occurred, both after neoadjuvant TT. Early data suggests improved RFS in those with pCR. Conclusions: Neoadjuvant targeted and immunotherapy are active regimens in clinical stage III melanoma patients and are associated with high pCR rate. Preliminary data suggest pCR correlates with improved RFS. Updated data will be presented. Clinical trial information: NCT02437279, NCT02231775, NCT02519322, NCT01972347.

Abstract P3-16-01: Immune characterization of inflammatory breast cancer and correlation to pathological complete response

Background:

Treatment of inflammatory breast cancer (IBC) includes neoadjuvant chemotherapy (NAC) followed by mastectomy and radiation. Responses are limited however with low pathological complete response (pCR) rates and poor survival. Recent RNA expression studies suggest that activated T cell signaling pathways and immunomodulatory markers such as PD-L1 are associated with a higher pCR rate in IBC; however comprehensive studies of tumor infiltrating lymphocytes (TIL) and protein expression of immunomodulatory molecules are lacking. There is a critical need therefore to study molecular and immune determinants of therapeutic response in IBC, with the goal of identifying biomarkers and actionable strategies to improve treatment outcomes.

Methods:

Baseline core biopsies from 36 IBC patients, 22 with stage III and 14 with stage IV disease were evaluated. Of these, 21 stage III and 10 stage IV patients underwent mastectomy following NAC, the latter for palliative purposes. Tumor subtype distribution was 14 patients with HER2-/HR-, 6 with HER2+/HR-, 11 with HER2-/HR+, and 5 with HER2+/HR+ disease. TIL infiltration in the tumor stroma was quantified on H&E slides based on consensus guidelines as well as by immunohistochemistry (IHC) staining for CD8. PD-L1 expression in the TIL and invasive tumor was evaluated by IHC in tumors with &gt;1%TIL.

Results:

Stromal TIL were found in the invasive tumor on pretreatment biopsies in 26 (72%) patients, with TIL percentages ranging from 1% to 60% (mean=11.6; sd=13.8); of note, 1 patient biopsy sample only had tumor emboli on the tissue block and therefore was not evaluable. Higher TIL infiltrate was noted in stage III versus stage IV disease (mean TIL 11.6% versus 3.5%, p=0.028). Mean TIL infiltrate was 11.5% in HER2-/HR-, 10.0% in HER2+/HR-, 10.4% in HER2+/HR+, and 3.6% in HER2-/HR+ tumors (p=NS). At mastectomy, 7/21 stage III patients and 1/10 stage IV patients achieved a pCR. Mean TIL was 13.4% in the pCR group versus 8.2% in the non-pCR group (p=0.37) CD8 and PD-L1 staining was performed on samples with &gt;1%TIL (n=15, of which 14 samples were available for additional staining). An average of 42% of TIL stained positive for CD8 (range 10-80%). There was no significant relationship between %CD8 and pCR, stage, or receptor status. None of these 14 patients demonstrated membranous PD-L1 positivity but all had focal weak cytoplasmic staining in the lymphocytes.

Conclusions:

Differences exist in the presence of stromal TIL in distinct groups within IBC (stage III versus stage IV disease and across histologic subtypes) and may contribute to differential responses to therapy. When comparing these results to published non-IBC literature (FinHER trial), our IBC patient cohort had lower TIL infiltrate in several histologic subtypes (HER2-/HR- 11.5% vs 25%, p=0.015), HER2+/HR-(10% vs 20%, p=0.10), and HER-/HR+ disease (3.6 vs 7.5%, p=0.01); TIL was comparable for HER2+/HR+ disease. Additional studies are underway (including multiplex analysis of myeloid and lymphoid markers, T cell receptor sequencing, and molecular profiling) in pre-treatment and surgical samples to better understand mechanisms of treatment response and resistance.

Citation Format: Reddy SM, Wargo JA, Reuben A, Reuben J, Woodward W, Ueno N, Mittendorf EA, Krishnamurthy S. Immune characterization of inflammatory breast cancer and correlation to pathological complete response [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-16-01.

Whole exome and whole transcriptome sequencing in melanoma patients to identify mechanisms of resistance to combined RAF/MEK inhibition

9015

Background: The RAF inhibitors vemurafenib and dabrafenib (D) and the MEK inhibitor trametinib (T) improve survival as monotherapies in BRAF-mutant melanoma. Since clinical mechanisms of resistance (MoR) result in MAPK pathway reactivation, recent efforts have focused on combined targeting of RAF and MEK. The combination of D and T (D/T) increased progression-free survival and response rate compared with D alone (Flaherty et al, NEJM, 2012). The MoR to this combination remain unknown. Methods: To look for clinical MoR to combined RAF/MEK inhibition, we performed whole exome (WES) and whole transcriptome sequencing (RNASeq) on tumors from 4 patients (pts) with acquired resistance and 1 pt with intrinsic resistance to D/T. Pre-treatment and post-resistance tumors from all pts were analyzed for point mutations, insertions/deletions, copy number alterations, alternatively spliced transcripts, rearrangements, and expression changes. Results: In 2 of 4 pts with acquired resistance, WES identified mutations in MEK1 and MEK2 that were undetectable in the pre-treatment tumors. In the 3rd pt, RNASeq identified an alternatively spliced isoform of BRAF lacking exons 2-10, also undetectable in the pre-treatment tumor. In the 4th pt, no obvious MoR were seen, though multiple alterations were enriched in the post-resistance tumor. The pt with intrinsic resistance had several alterations in genes that conferred resistance to RAF/MEK inhibition when overexpressed in BRAF-mutant cell lines. Integration of WES and RNASeq data also identified several co-existing alterations that may synergize to increase resistance. Conclusions: Analysis of combined WES and RNASeq data from pt samples provides a more complete picture of clinical MoR to MAPK-targeted therapy. Post-resistance tumors from 3 of 4 pts with acquired resistance to D/T had alterations in MAPK genes not detectable in the pre-treatment tumors, suggesting that resistance involves reactivation of the MAPK pathway despite combined RAF/MEK inhibition. Alternative dosing of current agents, more potent RAF/MEK inhibitors, and/or inhibition of the downstream kinase ERK may be needed for durable control of BRAF-mutant melanoma.

Surgical approach to pancreatic exocrine neoplasms

Pancreatic exocrine neoplasms represent a wide spectrum of pathophysiologic entities that challenge us as surgeons. The workup and management of these lesions continue to evolve as we better understand their complex nature. In this review, we will explore the contemporary clinical management of pancreatic adenocarcinoma, acinar cell carcinoma, and cystic neoplasms of the pancreas. The pathogenesis and epidemiology of these tumors will also be examined.