Treat it or Leave it: Immuno-Oncology in Mesothelioma Observed by the Eyes of Argus

Immunotherapy in Malignant Pleural Mesothelioma

The only registered systemic treatment for malignant pleural mesothelioma (MPM) is platinum based chemotherapy combined with pemetrexed, with or without bevacizumab. Immunotherapy did seem active in small phase II trials. In this review, we will highlight the most important immunotherapy-based research performed and put a focus on the future of MPM. PD-(L)1 inhibitors show response rates between 10 and 29% in phase II trials, with a wide range in progression free (PFS) and overall survival (OS). However, single agent pembrolizumab was not superior to chemotherapy (gemcitabine or vinorelbine) in the recent published PROMISE-Meso trial in pre-treated patients. In small studies with CTLA-4 inhibitors there is evidence for response in some patients, but it fails to show a better PFS and OS compared to best supportive care in a randomized study. A combination of PD-(L)1 inhibitor with CTLA-4 inhibitor seem to have a similar response as PD-(L)1 monotherapy. The first results of combining durvalumab (PD-L1 blocking) with cisplatin-pemetrexed in the first line are promising. Another immune treatment is Dendritic Cell (DC) immunotherapy, which is recently tested in mesothelioma, shows remarkable anti-tumor activity in three clinical studies. The value of single agent checkpoint inhibitors is limited in MPM. There is an urgent need for biomarkers to select the optimal candidates for immunotherapy among MPM patients in terms of efficacy and tolerance. Results of combination checkpoint inhibitors with chemotherapy are awaiting.

Prognostic influence of tumor microenvironment after hypofractionated radiation and surgery for mesothelioma

OBJECTIVE

Cytotoxic CD8+ tumor infiltrating lymphocytes (TILs) can contribute to the benefit of hypofractionated radiation, but programmed cell death pathways (programmed cell death 1 and programmed cell death ligand 1 [PD-1/PD-L1]) may provide a mechanism of tumor immune escape. We therefore reviewed the influence of PD-1/PD-L1 and CD8+ TILs on survival after accelerated hypofractionated hemithoracic radiation followed by extrapleural pneumonectomy for malignant pleural mesothelioma (MPM).

METHODS

Sixty-nine consecutive patients undergoing the protocol of Surgery for Mesothelioma after Radiation Therapy (SMART) between November 2008 and February 2016 were analyzed for the presence of PD-L1 on tumor cells, PD-1 on inflammatory cells, and CD8+ TILs. Comparison was made with a cohort of patients undergoing extrapleural pneumonectomy after induction chemotherapy (n = 14) and no induction (n = 2) between March 2005 and October 2008. PD-L1 expression on tumor cells ≥1% was considered positive. CD8+ TILs and PD-1 expression were scored as a percentage of positive cells.

RESULTS

PD-L1 was negative in 75% of MPM after completion of SMART. CD8+ TILs ranged between 0.24% and 8.47% (median 2%). CD8+ TILs ≥2% was associated with significantly better survival in epithelioid MPM (median survival 3.7 years vs 2.3 years in CD8+ TILs <2%; P = .02). PD-L1 positivity was associated with worse survival in biphasic MPM (median survival, 0.4 years vs 1.5 years in biphasic PD-L1 negative tumors; P = .07) after SMART. Multivariate analysis demonstrated that epithelioid MPM, nodal disease, and CD8+ TILs were independent predictors of survival after SMART.

CONCLUSIONS

The influence of tumor microenvironment on survival differs between epithelioid and nonepithelioid MPM. CD8+ TILs is an independent factor associated with better survival in epithelioid MPM treated with SMART.

Approved and emerging treatments of malignant pleural mesothelioma in elderly patients

Introduction: Malignant pleural mesothelioma (MPM) is a rare neoplasm with asbestos exposure as the dominant etiologic agent. Owing to the long latent period following exposure, MPM is often diagnosed late in life. Despite this, elderly patients are under-represented in clinical trials. To date, data regarding the tolerability and efficacy of anticancer treatments for elderly patients affected by MPM are still lacking.Areas covered: The current state-of-the-art of approved treatments employed in the treatment of MPM elderly patients is reviewed and discussed, with a look to emerging therapies. A structured search of bibliographic databases for peer-reviewed research literature and of main meeting abstracts using a focused review question was undertaken.Expert opinion: Even though the median age of MPM patients enrolled in the most recent experimental trials is increasing, no specific analysis has been reported so far in the elderly. Moreover, no data are available for the 'oldest of the elderly' (>75 years). Treatment of elderly patients with MPM is one of the major challenges to the clinician. There is a clear need of large, well-conducted retrospective studies and above all of prospective investigations in this patient population, both in the first-and in the second-line setting.

Redefining malignant pleural mesothelioma types as a continuum uncovers immune-vascular interactions

BACKGROUND

Malignant Pleural Mesothelioma (MPM) is an aggressive disease related to asbestos exposure, with no effective therapeutic options.

METHODS

We undertook unsupervised analyses of RNA-sequencing data of 284 MPMs, with no assumption of discreteness. Using immunohistochemistry, we performed an orthogonal validation on a subset of 103 samples and a biological replication in an independent series of 77 samples.

FINDINGS

A continuum of molecular profiles explained the prognosis of the disease better than any discrete model. The immune and vascular pathways were the major sources of molecular variation, with strong differences in the expression of immune checkpoints and pro-angiogenic genes; the extrema of this continuum had specific molecular profiles: a "hot" bad-prognosis profile, with high lymphocyte infiltration and high expression of immune checkpoints and pro-angiogenic genes; a "cold" bad-prognosis profile, with low lymphocyte infiltration and high expression of pro-angiogenic genes; and a "VEGFR2+/VISTA+" better-prognosis profile, with high expression of immune checkpoint VISTA and pro-angiogenic gene VEGFR2. We validated the gene expression levels at the protein level for a subset of five selected genes belonging to the immune and vascular pathways (CD8A, PDL1, VEGFR3, VEGFR2, and VISTA), in the validation series, and replicated the molecular profiles as well as their prognostic value in the replication series.

INTERPRETATION

The prognosis of MPM is best explained by a continuous model, which extremes show specific expression patterns of genes involved in angiogenesis and immune response.

Ipilimumab and nivolumab in the treatment of recurrent malignant pleural mesothelioma (INITIATE): results of a prospective, single-arm, phase 2 trial

BACKGROUND

Single-drug checkpoint inhibition has shown efficacy in patients with recurrent malignant pleural mesothelioma. Here, we assessed the safety and efficacy of the combination of nivolumab, an anti-programmed cell death 1 antibody, plus ipilimumab, an anti-cytotoxic T-lymphocyte protein 4 antibody, in patients with previously treated and relapsed malignant pleural mesothelioma.

METHODS

INITIATE was a prospective single-centre, single arm, phase 2 trial. Patients with malignant pleural mesothelioma who progressed after at least one line of platinum-containing chemotherapy were enrolled. Key eligibility criteria were measurable disease according to the modified Response Evaluation Criteria in Solid Tumours for mesotheliomas, Eastern Cooperative Oncology Group performance status 0 or 1, and adequate organ function. Patients received intravenous nivolumab (240 mg every 2 weeks) plus intravenous ipilimumab (1 mg/kg every 6 weeks up to four times). Treatment was continued for up to 2 years or until confirmed progression or unacceptable toxicity. The primary endpoint was disease control at 12 weeks. All patients who received at least one dose of therapy were included in safety analysis and all patients who received one dose of therapy and at least one radiological assessment were included in the primary analysis. This trial is registered at ClinicalTrials.gov, number NCT03048474.

FINDINGS

Between Oct 5, 2016, and Aug 3, 2017, 38 patients were enrolled in the study, of which two patients were excluded because they were not eligible for a biopsy. Of 36 eligible patients, one deteriorated before the start of the study so was not included in any analyses and one withdrew consent after one treatment cycle before radiological assessment so was included in the safety population only. 34 patients were evaluable for response assessment at 12 weeks. Of these, ten (29%) patients had a partial response and 13 (38%) patients had stable disease; thus, disease control was achieved by 23 (68%, 95% CI 50-83) of 34 patients. Treatment-related adverse events were reported in 33 (94%) patients. The most common adverse events were infusion-related reactions, skin disorders, and fatigue. Grade 3 treatment-related adverse events were reported in 12 (34%) of 35 patients.

INTERPRETATION

In this single-centre phase 2 trial, the combination of nivolumab plus ipilimumab showed marked efficacy in patients with recurrent malignant pleural mesothelioma. The safety profile was consistent with known data on the combination regimen. Our results warrant further investigation of this combination in a phase 3 trial.

FUNDING

Bristol-Myers Squibb.