Stereotactic Body Radiation Therapy for Oligoprogressive Pleural Mesothelioma: Fine-Tuning the Optimal Doses.

There is growing evidence of a role of stereotactic body radiation therapy (SBRT) in the treatment of patients with oligoprogressive pleural mesothelioma (PM). The objective of this study was to investigate the optimal radiation therapy doses and schedules in this setting. The records of patients treated with SBRT (>5 Gy per fraction) for oligoprogression of PM at 2 institutions from June 2014 to September 2022 were reviewed. Patients were divided into 2 groups: "intermediate-dose" SBRT (i-SBRT; total dose, 30-36 Gy in 5-6 fractions) and "high-dose" SBRT (h-SBRT; total dose, 45-50 Gy in 4-8 fractions). The comparison between the 2 groups in terms of local control (LC) and toxicity was the primary endpoint of the study. Overall, 23 patients were treated for 25 pleural lesions. All had received upfront chemotherapy with platinum/pemetrexed. Fifteen patients were treated with i-SBRT and 8 patients with h-SBRT. The median equivalent dose was 40 Gy (range, 40-49.6) in the i-SBRT group and 74.46 Gy (range, 64-88) in the h-SBRT group. Six-month, 1-year, and 2-year LC were 100%, 100%, and 80% in the i-SBRT group and 100%, 100%, and 67% in the h-SBRT group, respectively (p =.94). Only 2 patients (1 for each dose group) had a recurrence in the radiation therapy field, both after experiencing a distant relapse. No severe acute and late toxicities were observed in the i-SBRT group, whereas in the h-SBRT group, 2 patients experienced G2 acute and late thoracic pain and 1 patient experienced G2 acute and G3 chronic thoracic pain. In our experience, SBRT is a safe and effective option for selected patients with oligoprogressive PM. Use of intermediate total doses keeping the dose per fraction high seems to offer an excellent LC, avoiding the risk of severe toxicity.

Clinical outcomes of stereotactic body radiation therapy for malignant pleural mesothelioma.

BACKGROUND: The objective of this study is to determine the outcomes and toxicities of patients with malignant pleural mesothelioma (MPM) treated with stereotactic body radiotherapy (SBRT). MATERIALS AND METHODS: Data were extracted from an institutional tumor registry for patients diagnosed with mesothelioma and treated with SBRT. Kaplan-Meier and Cox regression analyses were employed to determine local control (LC) and overall survival (OS). RESULTS: Forty-four patients with 59 total treated tumors from December 2006 to April 2022 were identified. Fifty-one (86.4 %) cases had oligoprogressive disease (five sites or less). The median prescription dose delivered was 3000 cGy in 5 fractions (range: 2700-6000 cGy in 3-8 fractions). Fifty-one (86.4 %) tumors were in the pleura, 4 (6.8 %) spine, 2 (3.4 %) bone, 1 (1.7 %) brain, and 1 (1.7 %) pancreas. The median follow-up from SBRT completion for those alive at last follow-up was 28 months (range: 14-52 months). The most common toxicities were fatigue (50.8 %), nausea (22.0 %), pain flare (15.3 %), esophagitis (6.8 %), dermatitis (6.8 %), and pneumonitis (5.1 %). There were no grade ≥ 3 acute or late toxicities. There were 2 (3.4 %) local failures, one of the pleura and another of the spine. One-year LC was 92.9 % (95 % CI: 74.6-98.2 %) for all lesions and 96.3 % (95 % CI: 76.5-99.5 %) for pleural tumors. One-year LC was 90.9 % (95 % CI: 68.1-97.6 %) for epithelioid tumors and 92.1 % (95 % CI: 72.1-98.0 %) for oligoprogressive tumors. One-year OS from time of SBRT completion was 36.4 % (95 % CI: 22.6-50.3 %). On multivariable analysis, KPS was the lone significant predictor for OS (p = 0.029). CONCLUSIONS: Our single-institutional experience on patients with MPM suggests that SBRT is safe with a low toxicity profile and potentially achieve good local control.

Tumor-Targeted Nonablative Radiation Promotes Solid Tumor CAR T-cell Therapy Efficacy.

Infiltration of tumor by T cells is a prerequisite for successful immunotherapy of solid tumors. In this study, we investigate the influence of tumor-targeted radiation on chimeric antigen receptor (CAR) T-cell therapy tumor infiltration, accumulation, and efficacy in clinically relevant models of pleural mesothelioma and non-small cell lung cancers. We use a nonablative dose of tumor-targeted radiation prior to systemic administration of mesothelin-targeted CAR T cells to assess infiltration, proliferation, antitumor efficacy, and functional persistence of CAR T cells at primary and distant sites of tumor. A tumor-targeted, nonablative dose of radiation promotes early and high infiltration, proliferation, and functional persistence of CAR T cells. Tumor-targeted radiation promotes tumor-chemokine expression and chemokine-receptor expression in infiltrating T cells and results in a subpopulation of higher-intensity CAR-expressing T cells with high coexpression of chemokine receptors that further infiltrate distant sites of disease, enhancing CAR T-cell antitumor efficacy. Enhanced CAR T-cell efficacy is evident in models of both high-mesothelin-expressing mesothelioma and mixed-mesothelin-expressing lung cancer-two thoracic cancers for which radiotherapy is part of the standard of care. Our results strongly suggest that the use of tumor-targeted radiation prior to systemic administration of CAR T cells may substantially improve CAR T-cell therapy efficacy for solid tumors. Building on our observations, we describe a translational strategy of "sandwich" cell therapy for solid tumors that combines sequential metastatic site-targeted radiation and CAR T cells-a regional solution to overcome barriers to systemic delivery of CAR T cells.

One Third of Malignant Pleural Mesothelioma Shows High Immunohistochemical Expression of MSLN or CXCR4 Which Indicates Potent Candidates for Endo-Radiotherapy.

Malignant pleural mesothelioma (MPM) is a mainly asbestos-related tumour associated with a very poor prognosis. Therapeutic approaches include multimodal therapy and chemotherapeutics, with cisplatin being the drug of choice, but response rates of only up to 14% indicate very poor outcomes. Effective treatment options are lacking. Besides the diagnostic usage of radioligands in positron emission tomography (PET)/computed tomography (CT), the endo-radioligand therapy with Lu177 has been proven as a powerful tool in cancer therapy. Mesothelin (MSLN) and C-XC chemokine receptor 4 (CXCR4) are membrane-bound proteins, expressed in certain cancers, and thus are promising targets for endo-radiotherapy. A significant portion of high MSLN- or CXCR4-expressing tumors within the MPM may open the field for this sophisticated treatment approach in the near future. Formalin-fixed, paraffin-embedded (FFPE) tumour specimens from 105 patients suffering from MPM and treated at the Lung Cancer Centre of Essen and at the Helios Klinikum Emil von Behring Berlin were screened. The tumour samples were arranged in tissue microarrays. We immunohistochemically stained the tumour samples against MSLN and CXCR4. The protein expressions of the stainings were scored by a pathologist by using a semiquantitative method. The data obtained were correlated with the clinical outcome. Overall, 77.1% of the analysed tumours showed CXCR4 protein expression (25.7% of them at high expression level (Score 3)). 48.6% of all samples showed an overall strong staining (Score ≥ 2), 59% of the investigated tumours showed MSLN protein expression (10.5% of them at high expression (Score 3)), and 36.2% of all samples showed an overall strong staining (Score ≥ 2). Our results show significant tissue expression levels, for both CXCR4 and MSLN protein, in a major portion of clinical MPM samples. One-third of patients showed outstanding immunoexpression of at least one of these markers, making them interesting candidates for radioligand-based PET/CT diagnostics and follow-up and furthermore may profit from endo-radiotherapy.

Individualized prediction of survival benefit from postoperative radiotherapy for patients with malignant pleural mesothelioma.

OBJECTIVES: The role of postoperative radiotherapy (PORT) in malignant pleural mesothelioma (MPM) remains controversial and the eighth edition TNM staging scheme for MPM has not been fully verified. We aimed to develop an individualized prediction model for identifying optimal candidates for PORT among MPM patients who received surgery plus chemotherapy and externally validate the performance of the new TNM staging scheme. MATERIALS AND METHODS: Detailed characteristics of MPM patients during 2004-2015 were retrieved from SEER registries. Propensity score matching (PSM) was conducted to reduce disparities of baseline characteristics (age, sex, histologic type, stage, and type of surgery) between the PORT group and no-PORT group. A novel nomogram was constructed based on independent prognosticators identified by multivariate Cox regression model. The discriminatory performance and degree of calibration were evaluated. We stratified patients into different risk groups according to nomogram total scores and estimated the survival benefit of PORT in different subgroups in order to identify the optimal candidates. RESULTS: We identified 596 MPM patients, among which 190 patients (31.9%) received PORT. PORT conferred significant survival benefit in the unmatched population, while there was no significant survival difference favoring PORT in the matched population. The C-index of the new TNM staging scheme was closed to 0.5, which represented a poor discriminatory ability. A novel nomogram was constructed based on clinicopathological factors, including age, sex, histology, and N stage. We stratified patients into three risk groups. Subgroup analyses indicated that PORT was beneficial for high-risk group (p = 0.003) rather than low-risk group (p = 0.965) and intermediate-risk group (p = 0.661). CONCLUSION: We established a novel predictive model, which could make individualized prediction of survival benefit of PORT for MPM and could compensate for weakness in TNM staging system.

A novel pH sensitive theranostic PLGA nanoparticle for boron neutron capture therapy in mesothelioma treatment.

This study aims to develop poly lactic-co-glycolic acid (PLGA) nanoparticles with an innovative imaging-guided approach based on Boron Neutron Capture Therapy for the treatment of mesothelioma. The herein-reported results demonstrate that PLGA nanoparticles incorporating oligo-histidine chains and the dual Gd/B theranostic agent AT101 can successfully be exploited to deliver a therapeutic dose of boron to mesothelioma cells, significantly higher than in healthy mesothelial cells as assessed by ICP-MS and MRI. The selective release is pH responsive taking advantage of the slightly acidic pH of the tumour extracellular environment and triggered by the protonation of imidazole groups of histidine. After irradiation with thermal neutrons, tumoral and healthy cells survival and clonogenic ability were evaluated. Obtained results appear very promising, providing patients affected by this rare disease with an improved therapeutic option, exploiting PLGA nanoparticles.

Emerging Role of Immunomonitoring to Predict the Clinical Outcome of Patients With Malignant Pleural Mesothelioma Treated With Radical Radiation Therapy.

PURPOSE: The present study aimed at evaluating the baseline immune profile and the immunomodulating effects of radical hemithoracic radiation therapy (RT) in patients affected by malignant pleural mesothelioma (MPM) to identify potential predictive biomarkers of therapy response, toxicity development, and eligibility for further immunotherapeutic treatments. METHODS AND MATERIALS: Blood samples were collected from 55 patients with MPM, enrolled in a phase 3 trial comparing radical hemithoracic RT (interventional arm, n = 28) with local palliative RT (control arm, n = 27). Immunomonitoring was performed before RT, at the end of treatment, and 1 month after therapy, characterizing natural killer cells, B and T lymphocytes, activated CD4 and CD8 T cells, interferon-γ- and tumor necrosis factor-α-producing T helper (Th) 1 cells, regulatory T cells, and Th17 and Th22 lymphocytes, through flow cytometry. Serum levels of interleukin (IL)-6, -8, -10 and mesothelin were quantified through Enzyme-Linked Immunosorbent Assay (ELISA) assays at the same time points. Variations in the immune parameters were investigated by Friedman test and Wilcoxon signed rank post hoc test with Bonferroni correction for multiple testing, while the prognostic effect of immune biomarkers was evaluated through Kaplan-Meier method and Spearman's correlation analysis. RESULTS: Major immune variations were noticed after radical RT compared with palliative treatment, in particular an improvement in activated T cells and in interferon-γ-producing Th1 cells after RT. In the interventional arm, baseline high levels of Th22 and IL-10 and an increase in T cells were associated with an improved survival, whereas a fold increase in serum mesothelin correlated with the development of severe toxicity. An improvement of immunosuppressive regulatory T cells was observed in both arms of treatment. CONCLUSIONS: The immunomonitoring performed in patients with MPM revealed potential prognostic biomarkers for radical hemithoracic RT treatment and identified specific immune signatures induced by RT immunomodulation, which could suggest a synergistic effect with an immunotherapeutic treatment.

The Impact of Adjuvant Hemithoracic Radiation on Outcomes in Patients With Stage I-III Malignant Pleural Mesothelioma: A Dual Registry Analysis.

BACKGROUND: The outcomes associated with receipt of adjuvant radiation in patients after surgery for MPM are poorly understood. OBJECTIVE: The objective of this study was to use 2 registries to compare the outcomes of patients receiving adjuvant radiation or no radiation after definitive surgery for pathologic stage I-III MPM. METHODS: Patients with resected pathologic stage I-III MPM were identified from the Duke University registry (1996-2016) and National Cancer Database (NCDB) (2004-2015). The primary outcome was overall survival. Propensity score-matched and landmark subgroup analyses were performed. RESULTS: A total of 212 institutional and 1615 NCDB patients met criteria. In both cohorts, patients who underwent radiation were more likely to have margin-negative resection and more advanced pathologic stage. At a landmark time of 4.4 and 4.7 months from surgery, Duke [hazard ratio (HR) 1.14; 95% confidence interval (CI) 0.62-2.11] and NCDB patients (HR 0.97; 95% CI 0.81-1.17) who received adjuvant radiation did not experience improved survival compared to those who did not receive radiation in multivariable analysis. Duke patients who received radiation had similar incidence of recurrence and time to both overall recurrence and ipsilateral recurrence (HR 0.87; 95% CI 0.43-1.77) compared to those who did not. Duke patients experienced 100 grade 1/2, 21 grade 3/4, and one grade 5 toxicity events during radiation. CONCLUSIONS: In this dual registry analysis of patients with resected stage I-III MPM, the receipt of adjuvant hemithoracic radiation was not associated with improved survival compared to no radiation.

Molecular Radiotherapy with 177Lu-Immunoliposomes Induces Cytotoxicity in Mesothelioma Cancer Stem Cells In Vitro.

Malignant mesothelioma (MM) is a lethal tumor originating in the mesothelium with high chemotherapeutic resistance. Cancer stem cells (CSCs) persist in tumors and are critical targets responsible for tumor resistance and recurrence. The identification and characterization of CSCs may help develop effective treatment for MM. The objective of this study was to evaluate the therapeutic effect of molecular targeted radiotherapy by 177Lu-labeled immunoliposomes (177Lu-ILs) on CSCs of mesothelioma. MM CSCs were sorted based on CD26/CD24 expression level and their functional significances were established by small interference RNA. CSC potential of MM was evaluated for drug resistance, cell invasion, and cell growth rate in vitro. CSC metabolism was evaluated with the uptake of 18F-FDG. Therapeutic effects of 177Lu-labeled immunoliposomes targeting CD26 and CD24 were evaluated in vitro through proliferation and apoptotic assays. CSCs sorted from H28 cells exhibited significant drug resistance and enhanced proliferative activity as well as increased metabolism indicated by higher 18F-FDG uptake. Treatment with 177Lu-ILs, compared with 177Lu-CL and ILs, showed enhanced therapeutic effects on inhibition of proliferation, up-regulation of apoptosis, and suppression of CD26 and CD24 expression. Thus, our results suggest that molecular radiotherapy targeting both CD26 and CD24 could be a promising approach for CSC-targeting therapy for MM.

Survey of malignant pleural mesothelioma treatment in Japan: Patterns of practice and clinical outcomes in tomotherapy facilities.

We conducted a nationwide survey of tomotherapy for malignant pleural mesothelioma (MPM) in Japan. Fifty-six facilities were surveyed and data on 31 patients treated curatively between 2008 and 2017 were collected from 14 facilities. Twenty patients received hemithorax irradiation after extrapleural pneumonectomy (EPP) (first group). Five patients received irradiation without EPP (second group), while six received salvage radiotherapy for local recurrence (salvage group). Among the seven patients not undergoing EPP, five (four in the second group and one in the salvage group) were treated with lung sparing pleural irradiation (LSPI) and two with irradiation to visible tumors. Two-year overall survival (OS) rates in the first and second groups were 33% and 60%, respectively (median, 13 vs 30 months, P = 0.82). In the first and second groups, 2-year local control (LC) rates were 53 and 67%, respectively (P = 0.54) and 2-year progression-free survival (PFS) rates were 16% and 60%, respectively (P = 0.07). Distant metastases occurred in 15 patients in the first group and three in the second group. In the salvage group, the median OS was 18 months. Recurrence was observed in the irradiated volume in four patients. The contralateral lung dose was higher in LSPI than in hemithorax irradiation plans (mean, 11.0 ± 2.2 vs 6.1 ± 3.1 Gy, P = 0.002). Grade 3 or 5 lung toxicity was observed in two patients receiving EPP and hemithorax irradiation, but not in those undergoing LSPI. In conclusion, outcomes of EPP and hemithorax irradiation were not satisfactory, whereas LSPI appeared promising and encouraging.

Anticancer agent α-sulfoquinovosyl-acylpropanediol enhances the radiosensitivity of human malignant mesothelioma in nude mouse models.

Malignant pleural mesothelioma (MPM) is a highly malignant disease that develops after asbestos exposure. Although the number of MPM cases is predicted to increase, no effective standard therapies have been established. The novel radiosensitizer α-sulfoquinovosyl-acylpropanediol (SQAP) enhances the effects of γ-radiation in human lung and prostate cancer cell lines and in animal models. In this study, we explored the radiosensitizing effect of SQAP and its mechanisms in MPM. The human MPM cell lines MSTO-211H and MESO-4 were implanted subcutaneously into the backs and thoracic cavities of immunodeficient KSN/Slc mice, then 2 mg/kg SQAP was intravenously administered with or without irradiation with a total body dose of 8 Gy. In both the orthotopic and ectopic xenograft murine models, the combination of irradiation plus SQAP delayed the implanted human MSTO-211H tumor growth. The analysis of the changes in the relative tumor volume of the MSTO-211H indicated a statistically significant difference after 8 Gy total body combined with 2 mg/kg SQAP, compared to both the untreated control (P = 0.0127) and the radiation treatment alone (P = 0.0171). After the treatment in each case, immunostaining of the harvested tumors revealed decreased cell proliferation, increased apoptosis and normalization of tumor blood vessels in the SQAP- and irradiation-treated group. Furthermore, hypoxia-inducible factor (HIF) 1 mRNA and protein expression were decreased, indicating reoxygenation in this group. In conclusion, SQAP improved hypoxic conditions in tumor tissue and may elicit a radiosensitizing effect in malignant mesothelioma models.

Prophylactic irradiation of tracts in patients with malignant pleural mesothelioma: A systematic review and meta-analysis of randomized trials.

INTRODUCTION: The role of prophylactic irradiation of tracts (PIT) to prevent tumor seeding at the site of a diagnostic or therapeutic intervention in patients with malignant pleural mesothelioma (MPM) is controversial. This study aimed to determine the efficacy of PITs in preventing procedure tract metastases (PTM) after a chest wall procedure in MPM. MATERIALS AND METHODS: We searched various databases from inception date to April 2020 for randomized controlled trials (RCTs) comparing PIT with no PIT in patients who had a chest wall procedure for MPM. We assessed the risk of bias of individual RCT using the RoB2 tool. The primary outcome was the occurrence of PTM. Meta-analysis was performed using random-effects model. We employed the GRADE approach to assess the certainty of the evidence. RESULTS: We identified five RCTs including 737 patients. Two RCTs had a low risk of bias. PIT was associated with a significant reduction in the odds of PTM (odd ratio, 0.55; 95 % confidence interval, 0.32 to 0.95; P-value = 0.03; I2 = 13 %; GRADE: moderate certainty). One RCT reported no difference in overall survival outcome with the use of PIT. None of the RCTs performed subgroup analyses. Sensitivity analyses showed similar results when limited to RCTs with low risk of bias. CONCLUSION: PIT significantly reduces the occurrence of PTM in patients with MPM who had a diagnostic or therapeutic chest wall procedure.

Consensus Statement on Proton Therapy in Mesothelioma.

PURPOSE: Radiation therapy for mesothelioma remains challenging, as normal tissue toxicity limits the amount of radiation that can be safely delivered to the pleural surfaces, especially radiation dose to the contralateral lung. The physical properties of proton therapy result in better sparing of normal tissues when treating the pleura, both in the postpneumonectomy setting and the lung-intact setting. Compared with photon radiation, there are dramatic reductions in dose to the contralateral lung, heart, liver, kidneys, and stomach. However, the tissue heterogeneity in the thorax, organ motion, and potential for changing anatomy during the treatment course all present challenges to optimal irradiation with protons. METHODS: The clinical data underlying proton therapy in mesothelioma are reviewed here, including indications, advantages, and limitations. RESULTS: The Particle Therapy Cooperative Group Thoracic Subcommittee task group provides specific guidelines for the use of proton therapy for mesothelioma. CONCLUSIONS: This consensus report can be used to guide clinical practice, insurance approval, and future research.

Salvage radiotherapy for oligo-progressive malignant pleural mesothelioma.

OBJECTIVES: No standard treatment option is available for patients with unresectable malignant pleural mesothelioma (MPM) progressing after upfront chemotherapy. We aimed to explore the role of focal radiotherapy (FRT) as a treatment modality for oligo-progressive MPM. MATERIALS AND METHODS: In this retrospective study, consecutive patients pretreated with ≥1 lines of chemotherapy were included. Oligo-progressive MPM was defined as an unresectable disease with radiological progression at ≤3 sites according to a chest-abdominal contrast-enhanced computed tomography. Patients were treated with either stereotactic body radiotherapy (SBRT, ≥5 Gy per fraction) or hypo-fractionated radiotherapy (hypoRT, <5 Gy per fraction). Time to further systemic therapy (TFST) and local control (LC) after FRT were the primary endpoints. Biologically effective dose (BED) was calculated using three different alpha/beta models (1.5 Gy, 3 Gy and 10 Gy). RESULTS: From April 2006 to March 2019, 37 patients were treated on 43 pleural lesions; 16/37 (43 %) had undergone upfront multimodality treatment (MMT) including surgery. FRT was given in 22/37 (59.5 %) after one line of chemotherapy. SBRT was delivered for 26/43 lesions (60.5 %), hypoRT for 17/43 (39.5 %). Median TFST was 6 months (95 % CI 4.9-7.1). LC at 6 months and 1 year was 84 % and 76 %, respectively. Median TFST was longer in patients treated after 1 vs >1 line of chemotherapy (9 vs 4 months, p = 0.001) and in patients pretreated with MMT (6 vs 3 months, p = 0.021). Six-month LC was better in patients treated with a BED > 100 using alpha/beta 1.5 and 3. No ≥ G3 acute or late toxicities were reported. CONCLUSION: FRT was feasible in selected patients with oligo-progressive MPM, allowing delay of further systemic therapies, with no severe toxicity. FRT was more effective when performed at progression after one line of systemic therapy. Our results suggest a radio-resistant behavior of MPM.