Pleurectomy/decortication, chemotherapy, and intensity modulated radiation therapy for malignant pleural mesothelioma: rationale for multimodality therapy incorporating lung-sparing surgery

The Search for an Interesting Partner to Combine with PD-L1 Blockade in Mesothelioma: Focus on TIM-3 and LAG-3

Malignant pleural mesothelioma (MPM) is an aggressive cancer that is causally associated with previous asbestos exposure in most afflicted patients. The prognosis of patients remains dismal, with a median overall survival of only 9-12 months, due to the limited effectiveness of any conventional anti-cancer treatment. New therapeutic strategies are needed to complement the limited armamentarium against MPM. We decided to focus on the combination of different immune checkpoint (IC) blocking antibodies (Abs). Programmed death-1 (PD-1), programmed death ligand-1 (PD-L1), T-cell immunoglobulin mucin-3 (TIM-3), and lymphocyte activation gene-3 (LAG-3) blocking Abs were tested as monotherapies, and as part of a combination strategy with a second IC inhibitor. We investigated their effect in vitro by examining the changes in the immune-related cytokine secretion profile of supernatant collected from treated allogeneic MPM-peripheral blood mononuclear cell (PBMC) co-cultures. Based on our in vitro results of cytokine secretion, and flow cytometry data that showed a significant upregulation of PD-L1 on PBMC after co-culture, we chose to further investigate the combinations of anti PD-L1 + anti TIM-3 versus anti PD-L1 + anti LAG-3 therapies in vivo in the AB1-HA BALB/cJ mesothelioma mouse model. PD-L1 monotherapy, as well as its combination with LAG-3 blockade, resulted in in-vivo delayed tumor growth and significant survival benefit.

Dosimetric Correlates of Pulmonary Toxicity in Patients with Malignant Pleural Mesothelioma Receiving Radiation Therapy to the Intact Lungs

PURPOSE

We aimed to determine dose-volume constraints that correlate with severe (grade ≥3) radiation pneumonitis (RP) in patients diagnosed with malignant pleural mesothelioma, treated using volumetric modulated arc therapy.

METHODS AND MATERIALS

Data from 40 patients with malignant pleural mesothelioma who underwent pleurectomy decortication and adjuvant radiation therapy at our institution between December 2010 and October 2016 were retrospectively analyzed. Dosimetric variables for the absolute volume and percentage volume of the ipsilateral lung, contralateral lung, and heart were recorded. Events of RP were assessed using the Common Terminology Criteria for Toxicity and Adverse Events, version 4.0. The statistical analysis with Wilcoxon rank-sum, Spearman rank correlation, and receiver operating characteristic curves was computed using MATLAB V9.1, RV3.4, and SAS V9.4.

RESULTS

Of the 40 patients, 26 patients (65%) were male. The median age at the time of diagnosis was 66.5 years (range, 44-84 years). The median prescription dose was 45 Gy (range, 30-54 Gy). Five patients (12.5%) had grade ≥3 RP. The incidence of grade≥ 3 RP showed a significant correlation (P < .05) with the absolute volume and percentage volume of the ipsilateral lung spared of ≥20 Gy (55 cc; 7%) and spared of ≥30 Gy (200 cc; 23%). Dosimetric variables of the contralateral lung, total lung, and heart did not show a correlation with incidence of grade ≥3 RP.

CONCLUSIONS

In our cohort, sparing the ipsilateral lung of at least 55 cc of 20 Gy and 200 cc of 30 Gy correlated with a reduced incidence of severe (grade ≥3) RP.

Reduction of estradiol in human malignant pleural mesothelioma tissues may prevent tumour growth, as implied by in in-vivo and in-vitro models

This study aimed to investigate intratumoural estradiol and estrogen-receptors (ERα, ERβ and GPR30) in malignant pleural mesothelioma (MPM) to understand their function. Here, we report that immunohistochemistry of estradiol showed cytoplasmatic staining in 95% of fifty-seven human MPM samples with a trend toward a negative correlation between estradiol levels and the median post-diagnosis survival time. ERβ was only focally positive in 5.3% of cases, GPR30 and ERα were negative in our cases of MPM. GPR30 was detected mainly in glycosylated form in MPM cells. Moreover, G15, a GPR30 antagonist, induced MPM cell death. Altogether, these data suggest that MPM cells produce E₂ interact with glycosylated forms of GPR30, and this facilitates tumour growth. Estradiol was found in MPM cells and plasma from mice mesothelioma xenografts. Concurrent reduction in tumour mass and plasmatic estradiol levels were observed in the mice treated with exemestane, suggesting that the reduction of E₂ levels inhibit MPM growth. Thus, it appears that agents reducing estradiol levels could be useful to MPM therapy.

Failure patterns after hemithoracic pleural intensity modulated radiation therapy for malignant pleural mesothelioma

PURPOSE

We previously reported our technique for delivering intensity modulated radiation therapy (IMRT) to the entire pleura while attempting to spare the lung in patients with malignant pleural mesothelioma (MPM). Herein, we report a detailed pattern-of-failure analysis in patients with MPM who were unresectable or underwent pleurectomy/decortication (P/D), uniformly treated with hemithoracic pleural IMRT.

METHODS AND MATERIALS

Sixty-seven patients with MPM were treated with definitive or adjuvant hemithoracic pleural IMRT between November 2004 and May 2013. Pretreatment imaging, treatment plans, and posttreatment imaging were retrospectively reviewed to determine failure location(s). Failures were categorized as in-field (within the 90% isodose line), marginal (<90% and ≥50% isodose lines), out-of-field (outside the 50% isodose line), or distant.

RESULTS

The median follow-up was 24 months from diagnosis and the median time to in-field local failure from the end of RT was 10 months. Forty-three in-field local failures (64%) were found with a 1- and 2-year actuarial failure rate of 56% and 74%, respectively. For patients who underwent P/D versus those who received a partial pleurectomy or were deemed unresectable, the median time to in-field local failure was 14 months versus 6 months, respectively, with 1- and 2-year actuarial in-field local failure rates of 43% and 60% versus 66% and 83%, respectively (P=.03). There were 13 marginal failures (19%). Five of the marginal failures (38%) were located within the costomediastinal recess. Marginal failures decreased with increasing institutional experience (P=.04). Twenty-five patients (37%) had out-of-field failures. Distant failures occurred in 32 patients (48%).

CONCLUSIONS

After hemithoracic pleural IMRT, local failure remains the dominant form of failure pattern. Patients treated with adjuvant hemithoracic pleural IMRT after P/D experience a significantly longer time to local and distant failure than patients treated with definitive pleural IMRT. Increasing experience and improvement in target delineation minimize the incidence of avoidable marginal failures.