Clinical Outcomes of Patients With Metastatic NSCLC After Discontinuation of Immunotherapy Because of Immune-Related Adverse Effects.

Introduction: Immune checkpoint inhibition (ICI) is an important treatment modality in metastatic NSCLC and management of immunotherapy-related adverse effects (irAEs) can be challenging. Retreatment after discontinuation of ICI because of irAEs is a frequent clinical dilemma with limited available data. Methods: This single-center retrospective observational study reviewed the clinical course of 30 patients with metastatic NSCLC in whom ICI had to be discontinued owing to a serious irAE after an initial objective response to therapy. Results: After ICI discontinuation, 14 patients (47%) developed a durable response of more than 6 months, seven patients (23%) developed oligoprogression treated with local radiotherapy leading to disease control, six patients (20%) had progression of disease within 6 months, and three patients (10%) died owing to a severe irAE. Conclusions: A watchful waiting approach is justified after discontinuation of ICI owing to irAEs in patients with metastatic NSCLC with an initial response to therapy.

Immune monitoring in mesothelioma patients identifies novel immune-modulatory functions of gemcitabine associating with clinical response.

BACKGROUND: Gemcitabine is a frequently used chemotherapeutic agent but its effects on the immune system are incompletely understood. Recently, the randomized NVALT19-trial revealed that maintenance gemcitabine after first-line chemotherapy significantly prolonged progression-free survival (PFS) compared to best supportive care (BSC) in malignant mesothelioma. Whether these effects are paralleled by changes in circulating immune cell subsets is currently unknown. These analyses could offer improved mechanistic insights into the effects of gemcitabine on the host and guide development of effective combination therapies in mesothelioma. METHODS: We stained peripheral blood mononuclear cells (PBMCs) and myeloid-derived suppressor cells (MDSCs) at baseline and 3 weeks following start of gemcitabine or BSC treatment in a subgroup of mesothelioma patients included in the NVALT19-trial. In total, 24 paired samples including both MDSCs and PBMCs were included. We performed multicolour flow-cytometry to assess co-inhibitory and-stimulatory receptor- and cytokine expression and matched these parameters with PFS and OS. FINDINGS: Gemcitabine treatment was significantly associated with an increased NK-cell- and decreased T-regulatory cell proliferation whereas the opposite occurred in control patients. Furthermore, myeloid-derived suppressor cells (MDSCs) frequencies were lower in gemcitabine-treated patients and this correlated with increased T-cell proliferation following treatment. Whereas gemcitabine variably altered co-inhibitory receptor expression, co-stimulatory molecules including ICOS, CD28 and HLA-DR were uniformly increased across CD4+ T-helper, CD8+ T- and NK-cells. Although preliminary in nature, the increase in NK-cell proliferation and PD-1 expression in T cells following gemcitabine treatment was associated with improved PFS and OS. INTERPRETATION: Gemcitabine treatment was associated with widespread effects on circulating immune cells of mesothelioma patients with responding patients displaying increased NK-cell and PD-1 + T-cell proliferation. These exploratory data provide a platform for future on treatment-biomarker development and novel combination treatment strategies.

Depletion of Tumor-Associated Macrophages with a CSF-1R Kinase Inhibitor Enhances Antitumor Immunity and Survival Induced by DC Immunotherapy.

New immunotherapeutic strategies are needed to induce effective antitumor immunity in all cancer patients. Malignant mesothelioma is characterized by a poor prognosis and resistance to conventional therapies. Infiltration of tumor-associated macrophages (TAM) is prominent in mesothelioma and is linked to immune suppression, angiogenesis, and tumor aggressiveness. Therefore, TAM depletion could potentially reactivate antitumor immunity. We show that M-CSFR inhibition using the CSF-1R kinase inhibitor PLX3397 (pexidartinib) effectively reduced numbers of TAMs, circulating nonclassical monocytes, as well as amount of neoangiogenesis and ascites in mesothelioma mouse models, but did not improve survival. When combined with dendritic cell vaccination, survival was synergistically enhanced with a concomitant decrease in TAMs and an increase in CD8+ T-cell numbers and functionality. Total as well as tumor antigen-specific CD8+ T cells in tumor tissue of mice treated with combination therapy showed reduced surface expression of the programmed cell death protein-1 (PD-1), a phenomenon associated with T-cell exhaustion. Finally, mice treated with combination therapy were protected from tumor rechallenge and displayed superior T-cell memory responses. We report that decreasing local TAM-mediated immune suppression without immune activation does not improve survival. However, combination of TAM-mediated immune suppression with dendritic cell immunotherapy generates robust and durable antitumor immunity. These findings provide insights into the interaction between immunotherapy-induced antitumor T cells and TAMs and offer a therapeutic strategy for mesothelioma treatment. Cancer Immunol Res; 5(7); 535-46. ©2017 AACR.

Checkpoint Blockade in Lung Cancer and Mesothelioma.

In the last decade, immunotherapy has emerged as a new treatment modality in cancer. The most success has been achieved with the class of checkpoint inhibitors (CPIs), antibodies that unleash the antitumor immune response. After the success in melanoma, numerous clinical trials are being conducted investigating CPIs in lung cancer and mesothelioma. The programmed death protein (PD) 1-PD ligand 1/2 pathway and cytotoxic T lymphocyte-associated protein 4 are currently the most studied immunotherapeutic targets in these malignancies. In non-small cell lung cancer, anti-PD-1 antibodies have become part of the approved treatment arsenal. In small cell lung cancer and mesothelioma, the efficacy of checkpoint inhibition has not yet been proven. In this Concise Clinical Review, an overview of the landmark clinical trials investigating checkpoint blockade in lung cancer and mesothelioma is provided. Because response rates are around 20% in the majority of clinical trials, there is much room for improvement. Predictive biomarkers are therefore essential to fully develop the potential of CPIs. To increase efficacy, multiple clinical trials investigating the combination of cytotoxic T lymphocyte-associated protein 4 inhibitors and PD-1/PD ligand 1 blockade in lung cancer and mesothelioma are being conducted. Given the potential benefit of immunotherapy, implementation of current and new knowledge in trial designs and interpretation of results is essential for moving forward.

Precision immunotherapy; dynamics in the cellular profile of pleural effusions in malignant mesothelioma patients.

OBJECTIVES: Clinical studies have proven the potential of immunotherapy in malignancies. To increase efficacy, a prerequisite is that treatment is tailored, so precision immune-oncology is the logical next step. In order to tailor treatment, characterization of the patient's tumor environment is key. Pleural effusion (PE) often accompanies malignant pleural mesothelioma (MPM) and is an important part of the MPM environment. Furthermore, the composition of PE is used as surrogate for the tumor. In this study, we provide an insight in the dynamics of the MPM environment through characterization of PE composition over time and show that the immunological characteristics of PE do not necessarily mirror those of the tumor. MATERIALS AND METHODS: From 5 MPM patients, PE and tumor biopsies were acquired at the same time point. From one of these patients multiple PEs were obtained. PEs were acquired performing thoracocenteses and total cell amounts were determined. Immunohistochemistry was performed to quantify immune cell composition (T cells, macrophages) and tumor cells in PE derived cytospins and tumor biopsies. RESULTS: The PE amount and (immune) cellular composition varied considerably over time between multiple (n=10) thoracocenteses. These dynamics could in part be attributed to the treatment regimen consisting of standard chemotherapy and dendritic cell (DC)-based immunotherapy. In addition, the presence of T cells and macrophages in PE did not necessarily mirror the infiltration of these immune cells within tumor biopsies in 4 out of 5 patients. CONCLUSIONS: In this proof-of-concept study with limited sample size, we demonstrate that the composition of PE is dynamic and influenced by treatment. Furthermore, the immune cell composition of PE does not automatically reflect the properties of tumor tissue. This has major consequences when applying precision immunotherapy based on PE findings in patients. Furthermore, it implies a regulated trafficking of immune regulating cells within the tumor environment.

Pleural Effusion of Patients with Malignant Mesothelioma Induces Macrophage-Mediated T Cell Suppression.

INTRODUCTION: Clinical studies have demonstrated beneficial effects of immunotherapy in malignant pleural mesothelioma. The pleural cavity seems an attractive compartment to administer these types of therapies; however, local immunosuppressive mechanisms could hamper their efficacy. Macrophages are abundantly present within the mesothelioma microenvironment. This study investigates the influence of the macrophage phenotype, macrophages' capacity to inhibit local immune responses, and the decisive role of pleural effusion (PE) in this regard. METHODS: We cultured macrophages in the presence of PEs and investigated their phenotype. Macrophages and T cells were cocultured in the presence of PEs and tumor cell line supernatants. The levels of 11 cytokines and the prostanoid prostaglandin E2 were measured in PEs and supernatants. The presence and phenotype of macrophages and T cell subsets was measured in the PE of patients with mesothelioma. RESULTS: PE induced a tumor-promoting M2 phenotype in macrophages, which was confirmed by the suppressive activity of macrophages on T cell proliferation during coculture. Prostanoid prostaglandin E2 was identified as a potential inducer of the suppressive capacity of macrophages in PE. Macrophages isolated from PEs displayed an M2 phenotype and were negatively correlated with T cells in vivo. CONCLUSIONS: The current study demonstrates that macrophages in PE can play a pivotal role in directly hampering the antitumor T cell immune response. This emphasizes the potential of macrophages as a therapeutic target in mesothelioma and indicates that the presence and phenotype of macrophages in PE should be taken into consideration in the application of (intrapleural) immunotherapies.

Efficacy of Tumor Vaccines and Cellular Immunotherapies in Non-Small-Cell Lung Cancer: A Systematic Review and Meta-Analysis.

PURPOSE: Programmed cell death protein-1- checkpoint blockers have recently been approved as second-line treatment for advanced non-small-cell lung cancer (NSCLC). Unfortunately, only a subgroup of patients responds and shows long-term survival to these therapies. Tumor vaccines and cellular immunotherapies could synergize with checkpoint blockade, but which of these treatments is most efficacious is unknown. In this meta-analysis, we assessed the efficacy of tumor vaccination and cellular immunotherapy in NSCLC. METHODS: We searched for randomized controlled trials (RCTs) investigating cellular immunotherapy or vaccines in NSCLC. We used random effects models to analyze overall survival (OS) and progression-free survival (PFS), expressed as hazard ratios (HRs), and differences in time (months). The effect of immunotherapy type, disease stage, tumor histology, and concurrent chemotherapy was assessed using subgroup analysis and meta-regression. All procedures were performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. RESULTS: We identified 18 RCTs that matched our selection criteria; these included a total of 6,756 patients. Immunotherapy extended NSCLC survival and PFS, expressed as HR (OS: HR, 0.81, 95% CI, 0.70 to 0.94, P = .01; PFS: HR, 0.83, 95% CI, 0.72 to 0.95, P = .006) and month difference (OS: difference, 5.43 months, 95% CI, 3.20 to 7.65, P < .005; PFS: difference, 3.24 months, 95% CI, 1.61 to 4.88, P < .005). Cellular therapies outperformed tumor vaccines (OS as HR: P = .005, month difference: P < .001; PFS as HR: P = .001, month difference: P = .004). There was a benefit of immunotherapy in low-stage compared with high-stage NSCLC and with concurrent administration of chemotherapy only in one of four outcome measures evaluated (PFS in months: P = .01 and PFS as HR: P = .031, respectively). There was no significant effect of tumor histology on survival or PFS. CONCLUSION: Tumor vaccines and cellular immunotherapies enhanced OS and PFS in NSCLC. Cellular immunotherapy was found to be more effective than tumor vaccination. These findings have implications for future studies investigating combination immunotherapy in NSCLC.

Intratumoral macrophage phenotype and CD8+ T lymphocytes as potential tools to predict local tumor outgrowth at the intervention site in malignant pleural mesothelioma.

OBJECTIVES: In patients with malignant pleural mesothelioma (MPM), local tumor outgrowth (LTO) after invasive procedures is a well-known complication. Currently, no biomarker is available to predict the occurrence of LTO. This study aims to investigate whether the tumor macrophage infiltration and phenotype of and/or the infiltration of CD8+ T-cells predicts LTO. MATERIALS AND METHODS: Ten mesothelioma patients who developed LTO were clinically and pathologically matched with 10 non-LTO mesothelioma patients. Immunohistochemistry was performed on diagnostic biopsies to determine the total TAM (CD68), the M2 TAM (CD163) and CD8+ T-cell count (CD8). RESULTS: The mean M2/total TAM ratio differed between the two groups: 0.90±0.09 in the LTO group versus 0.63±0.09 in patients without LTO (p<0.001). In addition, the mean CD8+ T-cell count was significantly different between the two groups: 30 per 0.025 cm2 (range 2-60) in the LTO group and 140 per 0.025 cm2 (range 23-314) in the patients without LTO (p<0.01). CONCLUSION: This study shows that patients who develop LTO after a local intervention have a higher M2/total TAM ratio and lower CD8+ cell count at diagnosis compared to patients who did not develop this outgrowth. We propose that the M2/total TAM ratio and the CD8+ T-cell amount are potential tools to predict which MPM patients are prone to develop LTO.

Ratio of intratumoral macrophage phenotypes is a prognostic factor in epithelioid malignant pleural mesothelioma.

HYPOTHESIS: The tumor micro-environment and especially the different macrophage phenotypes appear to be of great influence on the behavior of multiple tumor types. M1 skewed macrophages possess anti-tumoral capacities, while the M2 polarized macrophages have pro-tumoral capacities. We analyzed if the macrophage count and the M2 to total macrophage ratio is a discriminative marker for outcome after surgery in malignant pleural mesothelioma (MPM) and studied the prognostic value of these immunological cells. METHODS: 8 MPM patients who received induction chemotherapy and surgical treatment were matched on age, sex, tumor histology, TNM stage and EORTC score with 8 patients who received chemotherapy only. CD8 positive T-cells and the total macrophage count, using the CD68 pan-macrophage marker, and CD163 positive M2 macrophage count were determined in tumor specimens prior to treatment. RESULTS: The number of CD68 and CD163 cells was comparable between the surgery and the non-surgery group, and was not related to overall survival (OS) in both the surgery and non-surgery group. However, the CD163/CD68 ratio did correlate with OS in both in the total patient group (Pearson r -0.72, p<0.05). No correlation between the number of CD8 cells and prognosis was found. CONCLUSIONS: The total number of macrophages in tumor tissue did not correlate with OS in both groups, however, the CD163/CD68 ratio correlates with OS in the total patient group. Our data revealed that the CD163/CD68 ratio is a potential prognostic marker in epithelioid mesothelioma patients independent of treatment but cannot be used as a predictive marker for outcome after surgery.

Immunotherapy prospects in the treatment of lung cancer and mesothelioma.

A very recent finding is the role of immune activation in cancer. The assumption that stimulating the patient's immune system to attack tumors is a valuable treatment option in malignant diseases has gained more acceptance. However the high immunosuppressive effects caused by the tumor limits this beneficial effect. There is a delicate balance between immunoactivation and immunosuppression in a patient. Especially in non small cell lung cancer (NSCLC), the role of immunosuppressive cells hampering immune activation is high. But also in small cell lung cancer (SCLC) and mesothelioma immunosuppressive activity is high. This is suggested to be related to the type of tumor, advanced stage of the disease, and the tumor load. In this review, we provide an overview of the progress and challenges in the immunotherapeutic approaches in lung cancer. We conclude with the concept that immunotherapy in thoracic malignancies must be tailored made to the balance of the immune system.

Dendritic cell-based immunotherapy in mesothelioma.

Mesothelioma is a rare thoracic malignancy with a dismal prognosis. Current treatment options are scarce and clinical outcomes are rather disappointing. Due to the immunogenic nature of mesothelioma, several studies have investigated immunotherapeutic strategies to improve the prognosis of patients with mesothelioma. In the last decade, progress in knowledge of the modulation of the immune system to attack the tumor has been remarkable, but the optimal strategy for immunotherapy has yet to be unraveled. Because of their potent antigen-presenting capacity, dendritic cells are acknowledged as a promising agent in immunotherapeutic approaches in a number of malignancies. This review gives an update and provides a future perspective in which immunotherapy may improve the outcome of mesothelioma therapy.