Dose-dependent pulmonary toxicity after postoperative intensity-modulated radiotherapy for malignant pleural mesothelioma

Radical hemithorax radiotherapy induces an increase in circulating PD-1+ T lymphocytes and in the soluble levels of PD-L1 in malignant pleural mesothelioma patients: a possible synergy with PD-1/PD-L1 targeting treatment?

Malignant Pleural Mesothelioma (MPM) is an aggressive tumor associated with asbestos exposure, characterized by a poor prognosis, managed with surgery, chemotherapy and radiotherapy. Recently, immunotherapy gives a survival advantage compared to chemotherapy, but limited to the non-epithelioid histotype, the rarest type. Radical hemithorax radiotherapy (RHRT) improves the Overall Survival (OS) of MPM patients, irrespective of histotype, and is able to induce immunomodulatory effects. In this study we aim to investigate changes in circulating T lymphocytes phenotype and activity, in MPM patients undergoing RHRT, to evaluate a possible therapeutic space for immunotherapy in this setting. To assess immunomodulatory effects of RHRT we evaluate peripheral blood samples of 35 MPM patients collected before treatment, at the end of RT, and 1 month later. We first notice that higher Lymphocyte-to-Monocyte Ratio (LMR) levels, before RT, are associated with an improved OS. The immune monitoring performed by ELISA assays reveals a significant increase in the serum levels of soluble PD-L1 (sPD-L1) and IFN-γ at the end of RHRT. Furthermore, the percentage of PD-1+ cells, evaluated by flow cytometry, significantly raise after RHRT in T cells, both CD4+ and CD8+. Also the proportion of proliferative cells is significantly expanded after RHRT in all T cell subtypes. After treatment we observe a significant increase in the number of patients showing WT-1 specific CD4+ T cells, measured by intracellular staining. The TCR repertoire analysis, investigated by Next Generation Sequencing, reveals an increased number of expanded T-cell clones after RHRT, and an association between TCR clonality and the percentage of proliferating cytotoxic T lymphocytes. The comparison of TCR sequences obtained in our cohort with those described in a literature cohort of MPM patients, reveals common entries, specific for MPM-associated antigens including WT-1. In this setting, pre-treatment levels of LMR seem to have a positive prognostic role, and RHRT would appear to induce immunomodulating effects, potential biomarkers for immunotherapy eligibility: i.e. increased PD-1+ T lymphocytes, proliferating T cells, expanded T cell clones and augmented levels of sPD-L1. These data suggest the design of a prospective study evaluating a maintenance immunotherapy after RHRT in MPM, even in the epithelioid histotype.

Impact of Neoadjuvant and Adjuvant Pleural Intensity-Modulated Radiotherapy in Multimodality Treatment for Malignant Pleural Mesothelioma

BACKGROUND

Few malignancies provoke as many controversies about treatment as pleural mesothelioma. There is limited experience with novel radiotherapy techniques worldwide in adjuvant and particularly in neoadjuvant settings within multimodality treatment. The objective of the current study was to investigate the long-term outcome of neoadjuvant and adjuvant pleural intensity-modulated radiotherapy (IMRT) combined with macroscopic complete resection with or without chemotherapy.

METHODS

We retrospectively analyzed a consecutive cohort of 59 patients who were diagnosed with pleural mesothelioma and underwent multimodality treatment including macroscopic complete resection and neoadjuvant or adjuvant IMRT between 2005 and 2019 at the Department of Thoracic Surgery, Medical University of Vienna, Austria.

RESULTS

In total, 59 patients (median age 59 years; IQR 54-66, male, n = 48; 81%) were included. Forty-seven patients underwent trimodality treatment consisting of induction chemotherapy, extrapleural pneumonectomy, and adjuvant IMRT. Novel neoadjuvant IMRT with (n = 9) or without (n = 3) chemotherapy followed by extrapleural pneumonectomy was performed in 12 patients. Median overall survival (OS) of all patients was 23.2 months (95% CI; 18.1-28.2) and 3- and 5-year survival rates were 33% and 28%, respectively. Survival was comparable between therapies including neoadjuvant versus adjuvant IMRT (median OS 17.5 vs. 24.0 months, p = 0.39).

CONCLUSIONS

Neoadjuvant pleural IMRT has been investigated as a novel treatment option for highly selected cases in pleural mesothelioma. Neoadjuvant IMRT was effective and safe in patients treated in a high-volume institution but showed no relevant survival benefit compared to adjuvant IMRT within multimodality treatment.

Role of radiotherapy in the management of rare solid thoracic tumors of the adults

Thoracic tumors include more than one hundred histopathological subtypes. Rare thoracic malignancies can be defined as representing less than 1% of all thoracic tumors. The European Rare Cancer Surveillance Project (RARECARE) identified rarity as an incidence less than 6 for 100,000 people, with significant difference of prevalence between them. Modalities of treatment for these pathologies include surgery, radiotherapy, and systemic therapies. In this article, we aim to discuss role and techniques of radiotherapy in management of rare solid thoracic tumors in adults, focusing on different anatomical locations such as lung parenchyma, mediastinum, vessels, chest wall and pleural cavity.

Consensus Quality Measures and Dose Constraints for Lung Cancer From the Veterans Affairs Radiation Oncology Quality Surveillance Program and ASTRO Expert Panel

PURPOSE

For patients with lung cancer, it is critical to provide evidence-based radiation therapy to ensure high-quality care. The US Department of Veterans Affairs (VA) National Radiation Oncology Program partnered with the American Society for Radiation Oncology (ASTRO) as part of the VA Radiation Oncology Quality Surveillance to develop lung cancer quality metrics and assess quality of care as a pilot program in 2016. This article presents recently updated consensus quality measures and dose-volume histogram (DVH) constraints.

METHODS AND MATERIALS

A series of measures and performance standards were reviewed and developed by a Blue-Ribbon Panel of lung cancer experts in conjunction with ASTRO in 2022. As part of this initiative, quality, surveillance, and aspirational metrics were developed for (1) initial consultation and workup; (2) simulation, treatment planning, and treatment delivery; and (3) follow-up. The DVH metrics for target and organ-at-risk treatment planning dose constraints were also reviewed and defined.

RESULTS

Altogether, a total of 19 lung cancer quality metrics were developed. There were 121 DVH constraints developed for various fractionation regimens, including ultrahypofractionated (1, 3, 4, or 5 fractions), hypofractionated (10 and 15 fractionations), and conventional fractionation (30-35 fractions).

CONCLUSIONS

The devised measures will be implemented for quality surveillance for veterans both inside and outside of the VA system and will provide a resource for lung cancer-specific quality metrics. The recommended DVH constraints serve as a unique, comprehensive resource for evidence- and expert consensus-based constraints across multiple fractionation schemas.

Image masking using convolutional networks improves performance classification of radiation pneumonitis for non-small cell lung cancer

Radiation pneumonitis (RP) is a serious side effect of radiotherapy in patients with locally advanced non-small-cell lung cancer (NSCLC). Image cropping reduces training noise and may improve classification accuracy. This study proposes a prediction model for RP grade ≥ 2 using a convolutional neural network (CNN) model with image cropping. The 3D computed tomography (CT) images cropped in the whole-body, normal lung (nLung), and nLung regions overlapping the region over 20 Gy (nLung∩20 Gy) used in treatment planning were used as the input data. The output classifies patients as RP grade < 2 or RP grade ≥ 2. The sensitivity, specificity, accuracy, and area under the curve (AUC) were evaluated using the receiver operating characteristic curve (ROC). The accuracy, specificity, sensitivity, and AUC were 53.9%, 80.0%, 25.5%, and 0.58, respectively, for the whole-body method, and 60.0%, 81.7%, 36.4%, and 0.64, respectively, for the nLung method. For the nLung∩20 Gy method, the accuracy, specificity, sensitivity, and AUC improved to 75.7%, 80.0%, 70.9%, and 0.84, respectively. The CNN model, in which the input image is segmented in the normal lung considering the dose distribution, can help predict an RP grade ≥ 2 for NSCLC patients after definitive radiotherapy.

Impact of Pleural Thickness on Occurrence of Postoperative Complications in Patients with Malignant Pleural Mesothelioma

OBJECTIVES

The rates of postoperative mortality and morbidity are high in patients with malignant pleural mesothelioma (MPM). Therefore, it is important to identify variables that increase the risk of postoperative complications. Pleural thickness has recently been identified as a prognostic indicator in patients with MPM. The aim of this study was to investigate clinical variables, including pleural thickness, that contribute to postoperative complications in patients with MPM.

PATIENTS AND METHODS

A total of 47 patients who underwent surgical excision of MPM between 2005 and 2021 were enrolled in this study. Correlations between postoperative complications within 90 days of surgery and preoperative clinical factors were investigated.

RESULTS

A total of 27 patients underwent extrapleural pneumonectomy (EPP), and the remaining 20 underwent pleurectomy/decortication (P/D). Macroscopic complete resections were obtained in all but three patients. Of the 47 patients, 23 (49%) experienced postoperative complications of grade 3 or worse. The major complication in patients with EPP was respiratory failure (n = 6), whereas the major complication in patients with P/D was prolonged air leakage (n = 7). Univariate logistic regression analysis found a correlation between postoperative complications and age, surgical side, and pleural thickness, while multivariate logistic regression analysis found surgical side (p = 0.04, 95% Cl 1.10-21.71, OR 4.90) and pleural thickness (p = 0.03, 95% Cl 1.21-23.00, OR 5.26) to significantly influence the occurrence of postoperative complications.

CONCLUSIONS

Pleural thickness has a significant effect on the occurrence of postoperative complications. Patients with thick pleura on the right side are at greater risk of postoperative complications.

Training and validation of a knowledge-based dose-volume histogram predictive model in the optimisation of intensity-modulated proton and volumetric modulated arc photon plans for pleural mesothelioma patients

BACKGROUND

To investigate the performance of a narrow-scope knowledge-based RapidPlan (RP) model for optimisation of intensity-modulated proton therapy (IMPT) and volumetric modulated arc therapy (VMAT) plans applied to patients with pleural mesothelioma. Second, estimate the potential benefit of IMPT versus VMAT for this class of patients.

METHODS

A cohort of 82 patients was retrospectively selected; 60 were used to "train" a dose-volume histogram predictive model; the remaining 22 provided independent validation. The performance of the RP models was benchmarked, comparing predicted versus achieved mean and near-to-maximum dose for all organs at risk (OARs) in the training set and by quantitative assessment of some dose-volume metrics in the comparison of the validation RP-based data versus the manually optimised training datasets. Treatment plans were designed for a prescription dose of 44 Gy in 22 fractions (proton doses account for a fixed relative biological effectiveness RBE = 1.1).

RESULTS

Training and validation RP-based plans resulted dosimetrically similar for both VMAT and IMPT groups, and the clinical planning aims were met for all structures. The IMPT plans outperformed the VMAT ones for all OARs for the contra-lateral and the mean and low dose regions for the ipsilateral OARs. Concerning the prediction performance of the RP models, the linear regression for the near-to-maximum dose resulted in Dachieved = 1.03Dpredicted + 0.58 and Dachieved = 1.02Dpredicted + 1.46 for VMAT and IMPT, respectively. For the mean dose it resulted: Dachieved = 0.99Dpredicted + 0.34 and Dachieved = 1.05Dpredicted + 0.27 respectively. In both cases, the linear correlation between prediction and achievement is granted with an angular coefficient deviating from unity for less than 5%. Concerning the dosimetric comparison between manual plans in the training cohort and RP-based plans in the validation cohort, no clinical differences were observed for the target volumes in both the VMAT and IMPT groups. Similar consistency was observed for the dose-volume metrics analysed for the OAR. This proves the possibility of achieving the same quality of plans with manual procedures (the training set) or with automated RP-based methods (the validation set).

CONCLUSION

Two models were trained and validated for VMAT and IMPT plans for pleural mesothelioma. The RP model performance resulted satisfactory as measured by the agreement between predicted and achieved (after full optimisation) dose-volume metrics. The IMPT plans outperformed the VMAT plans for all the OARs (with different intensities for contra- or ipsilateral structures). RP-based planning enabled the automation of part of the optimisation and the harmonisation of the dose-volume results between training and validation. The IMPT data showed a systematic significant dosimetric advantage over VMAT. In general, using an RP-based approach can simplify the optimisation workflow in these complex treatment indications without impacting the quality of plans.

Feasibility of Tumor Treating Fields with Pemetrexed and Platinum-Based Chemotherapy for Unresectable Malignant Pleural Mesothelioma: Single-Center, Real-World Data

Simple Summary

Management of malignant pleural mesothelioma (MPM) is challenging as patients frequently present with unresectable disease and the response rates with systemic therapy alone remain low. Given the paucity of effective therapies for MPM, Tumor Treating Fields (TTFields) therapy was made available for use under an FDA-approved Humanitarian Device Exemption (HDE) protocol in 2019, but no real-world data beyond the initial trial have been published to date. We reviewed our retrospective series of five patients diagnosed with MPM and treated with TTFields with pemetrexed and platinum-based chemotherapy. This therapy resulted in a modest disease-stabilization rate with no significant device-related major toxicities. However, we observed universal low-grade skin toxicities related to the device which required medical management and self-discontinuation in 2/5 patients. We also observed lower device usage, compared to the STELLAR trial. Both of these represent opportunities for developing improved management guidelines and efforts to improve patient compliance.

Abstract

Purpose: The objectives of this study were to evaluate the implementation, device usage rates, clinical outcomes, and treatment-related toxicities associated with TTFields and pemetrexed plus platinum-based chemotherapy in patients with unresectable MPM, outside the initial trial results. Methods: Consecutive patients with unresectable MPM were enrolled onto an FDA-required HDE protocol from 2019 to 2021. All patients were treated with a protocol-defined regimen of continuous TTFields (150 kHz) and pemetrexed plus platinum-based chemotherapy. Results: Five patients with unresectable MPM were enrolled. The median number of 4-week TTFields cycles was 5 (range: 2–7 cycles). Median TTFields device usage in the first 3 months was 12.5 h per day (range: 5–16.8 h), representing 52% (21–70%) of the potential daily duration. The median follow-up was 5.4 months (range: 1.1–20.9 months). Treatment-related dermatitis was the only side effect associated with TTFields and was reported as grade 1–2 in all patients; no patient had grade 3+ device-related toxicities. Conclusions: This study represents the first results of real-world implementation of TTFields for MPM. In comparison to the initial clinical trial (STELLAR), compliance rates were lower, although skin-related toxicities appeared similar. Further initiatives and guidelines should be developed to manage treatment-related dermatitis and improve device usage.

New Era for Malignant Pleural Mesothelioma: Updates on Therapeutic Options

Malignant pleural mesothelioma (MPM) is a rare malignancy with few treatment options. Recent advances have led to US Food and Drug Administration approvals and changes in the standard of care with a novel biomedical device approved for use with platinum-pemetrexed, and also for immunotherapy agents to be included as a frontline treatment option in unresectable disease. Although predictive biomarkers for systemic therapy are not currently in use in clinical practice, it is essential to correctly identify the MPM histology to determine an optimal treatment plan. Patients with nonepithelioid MPM may have a greater magnitude of benefit to dual immunotherapy checkpoint inhibitors and this regimen should be preferred in the frontline setting for these patients. However, all patients with MPM can derive benefit from immunotherapy treatments, and these agents should ultimately be used at some point during their treatment journey. There are ongoing studies in the frontline unresectable setting that may further define the frontline therapy space, but a critical area of research will need to focus on the immunotherapy refractory population. This review article will describe the new developments in the areas of biology with genomics and chromothripsis, and also focus on updates in treatment strategies in radiology, surgery, radiation, and medical oncology with cellular therapies. These recent innovations are generating momentum to find better therapies for this disease.

GOECP/SEOR clinical guidelines on radiotherapy for malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare tumor with poor prognosis and rising incidence. Palliative care is common in MPM as radical treatment with curative intent is often not possible due to metastasis or extensive locoregional involvement. Numerous therapeutic advances have been made in recent years, including the use of less aggressive surgical techniques associated with lower morbidity and mortality (e.g., pleurectomy/decortication), technological advancements in the field of radiotherapy (intensity-modulated radiotherapy, image-guided radiotherapy, stereotactic body radiotherapy, proton therapy), and developments in systemic therapies (chemotherapy and immunotherapy). These improvements have had as yet only a modest effect on local control and survival. Advances in the management of MPM and standardization of care are hampered by the evidence to date, limited by high heterogeneity among studies and small sample sizes. In this clinical guideline prepared by the oncological group for the study of lung cancer of the Spanish Society of Radiation Oncology, we review clinical, histologic, and therapeutic aspects of MPM, with a particular focus on all aspects relating to radiotherapy, including the current evidence base, associations with chemotherapy and surgery, treatment volumes and planning, technological advances, and reradiation.

Prediction of radiation pneumonitis after definitive radiotherapy for locally advanced non-small cell lung cancer using multi-region radiomics analysis

To predict grade ≥ 2 radiation pneumonitis (RP) in patients with locally advanced non-small cell lung cancer (NSCLC) using multi-region radiomics analysis. Data from 77 patients with NSCLC who underwent definitive radiotherapy between 2008 and 2018 were analyzed. Radiomic feature extraction from the whole lung (whole-lung radiomics analysis) and imaging- and dosimetric-based segmentation (multi-region radiomics analysis) were performed. Patients with RP grade ≥ 2 or < 2 were classified. Predictors were selected with least absolute shrinkage and selection operator logistic regression and the model was built with neural network classifiers. A total of 49,383 radiomics features per patient image were extracted from the radiotherapy planning computed tomography. We identified 4 features and 13 radiomics features in the whole-lung and multi-region radiomics analysis for classification, respectively. The accuracy and area under the curve (AUC) without the synthetic minority over-sampling technique (SMOTE) were 60.8%, and 0.62 for whole-lung and 80.1%, and 0.84 for multi-region radiomics analysis. These were improved 1.7% for whole-lung and 2.1% for multi-region radiomics analysis with the SMOTE. The developed multi-region radiomics analysis can help predict grade ≥ 2 RP. The radiomics features in the median- and high-dose regions, and the local intensity roughness and variation were important factors in predicting grade ≥ 2 RP.

Use of Continuous Positive Airway Pressure (CPAP) to Limit Diaphragm Motion-A Novel Approach for Definitive Radiation Therapy for Inoperable Pleural Mesothelioma: A Pilot Study

Simple Summary

Radiotherapy is an important part of the multimodality approach to treating malignant pleural mesothelioma. In recent studies there is a new trend to treat patients with intact lungs instead of following surgery. This treatment creates significant concerns regarding lung toxicity. We describe two methods to reduce that toxicity. One is the use of constant pulmonary airway pressure (CPAP) to inflate the lungs during treatment. The second is utilizing a novel method of planning and delivering radiotherapy called volumetric modulated arc therapy (VMAT).

Abstract

Malignant pleural mesothelioma (MPM) is a deadly disease and radiotherapy (RT) plays an important role in its management. Recent developments in technique have made it is possible to deliver RT to MPM in the intact lung. However, it is imperative to reduce normal lung doses. We present a pilot study examining the use of CPAP and VMAT radiotherapy to reduce toxicity when treating MPM, involving three consecutive patients with MPM, not amenable to surgery, who were treated according to Helsinki committee approval. Patients were simulated using four-dimentional CT simulation with the assistance of CPAP lung inflation, then were treated using both IMRT and VMAT techniques. Radiation lung dose was optimized based on accepted lung dose constraints. Patients were followed for toxicity as well as local control and survival. Results: Three patients were treated with CPAP-based IMRT treatment. These patients tolerated the treatment and DVH constraints were able to be met. The comparison plans among the four VMAT arcs and the IMRT static field treatment were able to accomplish the treatment planning objectives without significant advantages with either technique. The treatment combined with CPAP reduced the normal lung dose in MPM patients with intact lungs. This technique is worthy of further investigation.

Epidemiology, diagnosis and treatment of the malignant pleural mesothelioma, a narrative review of literature

The malignant pleural mesothelioma is a very aggressive tumor which is arising from mesothelial cells and is associated with asbestos exposure. It is a heterogeneous cancer that shows a complex pattern of molecular changes, including genetic, chromosomic, and epigenetic abnormalities. The malignant pleural mesothelioma is characterized by a silent and slow clinical progression with an average period of 20–40 years from the asbestos exposure phase to the start of the symptoms. Unfortunately, to date, the therapeutic options are very limited, especially if the tumor is detected late. This narrative review provides an extended overview of the present evidence in the literature regarding the epidemiology, diagnostic pathways and treatment approaches of the malignant pleural mesothelioma. The treatment of mesothelioma has evolved slowly over the last 20 years not only from a surgical point of view but also radiotherapy, chemotherapy and immunotherapy play nowadays a key role. Several surgical strategies are available ranging from extrapleural pneumonectomy to cytoreductive surgery but a multidisciplinary approach seems to be mandatory because a single approach has not proved to date to be resolutive. New non-surgical treatment options appear to be promising but the results have to be taken in account with caution because clear evidence with high-quality studies is still lacking

Locoregional control and toxicity after pleurectomy/decortication and intensity-modulated pleural radiation therapy in patients with malignant pleural mesothelioma

Background

Treatment of malignant pleural mesothelioma (MPM) represents a major challenge for oncologists. Multimodality treatment, which generally involves induction chemotherapy, surgery and radiotherapy have recently shown promising results. The aim of this study was to evaluate the locoregional control and toxicity of intensity modulated radiotherapy (IMRT) after pleurectomy and decortication (P/D) as part of trimodality therapy for patients with locally advanced MPM.

Methods

We prospectively analyzed data from 20 patients with MPM treated at a single tertiary‐care institution. Initially every patient received induction chemotherapy with platinum‐based chemotherapy. After chemotherapy, patients without progression underwent P/D, and if feasible, hemi‐thoracic IMRT was administered at a planned dose of 50.4–54 Gy in 28–30 fractions and treated with 9–11 noncoplanar fields.

Results

A total of 15 of the 20 enrolled patients underwent P/D followed by IMRT to the hemi‐thoracic cavity. The median total radiotherapy dose was 48.7 Gy (23.4–54 Gy). Radiation pneumonitis (RP) developed in nine patients (60%), and of these, two patients (13.3%) experienced G3 or G4 RP. The estimated locoregional‐relapse‐free survival at two years was 75.9%, and the main pattern of recurrence was distant (72.7%). For the entire cohort median follow‐up was 22.7 months, median progression‐free survival was 18.9 months and median overall survival 23.6 months.

Conclusions

Platinum‐based chemotherapy followed by lung‐sparing surgery (P/D) and IMRT is a feasible and safe treatment modality that yields acceptable locoregional control in patients with locally advanced MPM; however, these results should be corroborated in larger studies.

Radiation Therapy for Malignant Pleural Mesothelioma

The treatment of malignant pleural mesothelioma with radiation therapy has always been a technical challenge. For many years, radiation therapy was delivered after extrapleural pneumonectomy with acceptable results. As the utilization of pleurectomy/decortication increased, techniques, such as pleural intensity-modulated radiation therapy (IMRT) have been introduced. The experience with these techniques have grown and multiple trials using IMRT, both in the setting of extrapleural pneumonectomy or pleurectomy, are being conducted to assess its effectiveness.

RapidPlan for Knowledge-Based Planning of Malignant Pleural Mesothelioma

PURPOSE

Treatment planning for malignant pleural mesothelioma is a challenging task due to the relatively large size of the target and the need to spare critical organs that overlap with or are within the target volume. We aimed to develop a knowledge-based model using RapidPlan (RP) for patients with 2 intact lungs.

METHODS AND MATERIALS

Data from 57 patients treated with volumetric modulated arc therapy were chosen for training the dose estimation model at a single dose level. The prescription dose was 50.4 Gy in 1.8 Gy fractions. The model was validated on 23 new patients by comparing the clinical plan to the RP. Time taken to plan the RP was compared with that for the clinical plan.

RESULTS

For similar target coverage and plan inhomogeneity, RP significantly improved the sparing of the contralateral lung, heart, stomach, esophagus, and ipsilateral kidney. On average, the contralateral lung V5 Gy and V10 Gy were reduced by 13.9% (P < .001) and 7.9% (P < .001), respectively. The mean heart dose was reduced by 5 Gy (P < .001) and V30 Gy by 9.1% (P < .001). Mean dose to the stomach and esophagus were both reduced by 5 Gy (P < .001), and the ipsilateral kidney V18 Gy by 4.1% (P < .001). Mean total lung dose was reduced by 0.8 Gy with RP, which enabled an increase in prescription dose by 1 fraction Absolute volume of ipsilateral lung was adequately spared by both techniques, while sparing of all other organs, namely the cord, liver, and bowel, was not compromised with RP. Time taken with RP was 20 minutes, 45 seconds versus at least 4 hours for an experienced treatment planner.

CONCLUSIONS

The RP model for malignant pleural mesothelioma showed improved sparing of critical organs with a reduced treatment planning time and increased prescription dose.

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.

Disease-Related Outcomes and Toxicities of Intensity Modulated Radiation Therapy After Lung-Sparing Pleurectomy for Malignant Pleural Mesothelioma: A Systematic Review

PURPOSE

This review explores the use of intensity modulated radiation therapy (IMRT) after lung-sparing surgery in malignant pleural mesothelioma (MPM). Because severe toxicities have been documented after radiation therapy for MPM, its use remains controversial, especially as modern surgical management has shifted toward lung-sparing pleurectomy/decortication. IMRT is an advanced technique that may allow for safer radiation therapy delivery, but there remains limited data (including no summative data) to support this notion.

METHODS AND MATERIALS

We performed a systematic review evaluating the safety and efficacy of post-pleurectomy IMRT (P-IMRT). A systematic review of PubMed using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was conducted for publications of all dates that specifically reported clinical outcomes and/or toxicities of P-IMRT in patients with MPM. Ten original studies were included in this review.

RESULTS

The incidence of grade 3 pneumonitis ranged from 0% to 16%, with all but 2 studies reporting rates below 9%. Grade 4 and 5 pneumonitis were observed in less than 1.5% of cases, except in one publication that used hypofractionated radiation therapy to doses >60 Gy. Crude local failure rates ranged from 19% to 60%, median progression free survival ranged from 12 to 16 months, and median overall survival ranged from 19 to 28 months.

CONCLUSIONS

P-IMRT produces relatively few higher-grade toxicities and has reasonable disease-related outcomes, especially when delivered using conventionally fractionated regimens to doses of 45 to 54 Gy and exercising careful attention to dose constraints during treatment planning. IMRT can thus be considered in well-selected patients in whom adequate survival after pleurectomy is expected. These data also support the initiation of the phase III NRG-LU006 trial of extended pleurectomy/decortication and chemotherapy with or without IMRT.

Dosimetric Comparison of Lung-Sparing Radiation Therapy between Volumetric Arc Therapy and Helical Tomotherapy for Unresectable Malignant Pleural Mesothelioma

Objective

To compare volumetric arc therapy (VMAT) and helical tomotherapy (HT) plans in terms of dosimetric parameters in positron emission tomography- (PET-) computerized tomography- (CT-) based radiation therapy planning in unresectable malignant pleural mesothelioma (MPM).

Methods

CT and coregistered PET-CT data from seven patients with histologically-proven MPM were utilized for VMAT and HT plans. Target volumes and organs at risk (OARs) were delineated. The prescription doses for planning target volume 1 (PTV₁) and PTV₂ were 45.0 Gy and 54 Gy in 1.8 Gy/fr, respectively. Each technique was evaluated in terms of target volume coverage and OAR doses.

Findings

Although the maximum (p=0.001) and mean (p < 0.001) doses of PTV₁, and PTV₂ (p < 0.001 for maximum and p=0.001 for mean doses) favored the HT technique over VMAT, both techniques efficiently covered the target volumes. Additionally, HT also provided more homogeneous dose distribution (p < 0.001) and numerically lower doses received by most OARs, but again both rotational techniques were successful in keeping the OAR doses below the universally accepted limits. The major disadvantage of the HT technique was the requirement for longer treatment times (7.4 versus 2.5 minutes/fr; p < 0.001) to accomplish the intended treatment.

Conclusion

Results of this dosimetric comparison clearly demonstrated the possibility of safe hemithoracic irradiation of medically/technically unresectable MPM patients with either of the two rotational RT techniques, namely the VMAT and HT. Clinically, considering their poor prognosis, these promising findings may open a potential new window for curative treatment of unresectable MPM patients, if further confirmed by future clinical studies.

Cardiotoxicity of mediastinal radiotherapy

Aim

To explore available recent literature related to cardiotoxicity following mediastinal radiation.

Background

Radiotherapy-related heart injury is well documented, with no apparent safety threshold dose. The number of long-term cancer survivors exposed to mediastinal radiotherapy at some point of their treatment is increasing. Heart dosimetric parameters are of great importance in developing a treatment plan, but few data are available regarding radiosensitivity and dose-volume constraints for specific heart structures.

Materials and Methods

In October 2018, we identified articles published after 1990 through a PubMed/MEDLINE database search. The authors examined rough search results and manuscripts not relevant for the topic were excluded. We extracted clinical outcomes following mediastinal radiotherapy of childhood cancers, lymphoma, medulloblastoma, thymic cancers and hematopoietic cell transplantation survivors and evaluated treatment planning data, whenever available.

Results

A total of 1311 manuscripts were identified in our first-round search. Of these manuscripts, only 115 articles, matching our selection criteria, were included.

Conclusions

Studies uniformly show a linear radiation dose-response relationship between mean absorbed dose to the heart (heart-D_mean) and the risk of dying as a result of cardiac disease, particularly when heart-D_mean exceeds 5 Gy. Limited data are available regarding dose-volume predictors for heart substructures and the risk of subsequent cardiac toxicity. An individual patient's cardiotoxicity risk can be modified with advanced treatment planning techniques, including deep inspiration breath hold. Proton therapy is currently showing advantages in improving treatment planning parameters when compared to advanced photon techniques in lymphoma, thymic malignancies, malignant mesothelioma and craniospinal irradiation.

Fatal Radiation Pneumonitis: Literature Review and Case Series

Purpose

Fatal radiation pneumonitis is a rare event. In recent years, higher incidences of grade 5 pneumonitis have been reported. Based on 3 cases in our clinic, a literature review was performed to assess specific clinical features and risk factors for fatal pneumonitis.

Methods and Materials

Three patients with nonsmall cell lung cancer were treated with conventionally fractionated radiation therapy, 2 with volumetric modulated arc therapy and one with intensity modulated radiation therapy. All 3 patients had high volumes of 5 Gy in the total lung and contralateral lungs. Patients died of pneumonitis between 2 and 5 months after the end of radiation therapy. A literature review focused on grade 5 pneumonitis was performed for conventionally fractioned and stereotactic radiation therapy for lung cancer.

Results

Patients with grade 5 pneumonitis develop symptoms sooner than lower grade pneumonitis. Symptoms often do not respond to steroid treatment or return after steroid taper. Imaging features extend beyond the high dose area and involve the contralateral lung. Dosimetric risk factors include both low dose and high dose lung volumes. For patients undergoing stereotactic radiation therapy interstitial lung disease has been described as a risk factor.

Conclusions

Despite decades of investigating radiation pneumonitis, the question of the optimum dose distribution in the lung, a large dose to a small volume versus a small dose to a large volume, is still unresolved. When both low and high dose lung volume constraints are followed, the risk for grade 5 pneumonitis has been shown to be low even with intensity modulated radiation therapy and concurrent chemotherapy. In addition to dose factors, underlying clinical and radiographic parameters play an important role for the development of grade 5 pneumonitis.

The Role of Adjuvant Radiotherapy in the Treatment of Pleural Mesothelioma

BACKGROUND

Pleural mesothelioma is a rare but aggressive form of cancer. Local recurrence represents the majority of treatment failures and overall survival (OS) outcomes remain dismal. Adding locoregional treatment with radiotherapy after surgical resection has been considered but its role remains uncertain.

OBJECTIVE

The purpose of this study was to evaluate the outcomes of adjuvant radiation therapy (RT) for patients with malignant pleural mesothelioma.

METHODS

The National Cancer Data Base (NCDB) was queried (2004-2013) for patients with malignant mesothelioma. Patients were divided into three groups: observation, surgery alone, and surgery followed by adjuvant RT. Statistics included Fisher's exact or Chi square tests to analyze categorical proportions between groups, Kaplan-Meier analysis to evaluate OS, and Cox proportional hazards modeling to determine variables associated with OS. Propensity matching was performed to make comparisons between homogenous groups.

RESULTS

Overall, the surgery plus radiotherapy group had a higher median survival (21.4 months) compared with surgery alone (16.59 months) [p < 0.001]. RT was more likely to be delivered after extrapleural pneumonectomy than with lung-sparing surgical approaches. On multivariable analysis, receipt of surgery plus radiotherapy, chemotherapy administration, and higher socioeconomic status were associated with improved OS (p < 0.0001). After propensity matching, receipt of surgery plus radiotherapy and chemotherapy administration were still associated with improved OS (p < 0.05).

CONCLUSIONS

In the treatment of malignant pleural mesothelioma, adjuvant radiotherapy after surgical intervention was associated with improved OS. This study is the largest study of adjuvant radiotherapy to date, and our findings highlight the need for additional prospective data.

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.

A Novel Prospective Study Assessing the Combination of Photodynamic Therapy and Proton Radiation Therapy: Safety and Outcomes When Treating Malignant Pleural Mesothelioma

Malignant pleural mesothelioma remains difficult to treat, with high failure rates despite optimal therapy. We present a novel prospective trial combining proton therapy (PT) and photodynamic therapy (PDT) and the largest-ever mesothelioma PT experience (n = 10). PDT photosensitizers included porfimer sodium (2 mg·kg-1 ; 24 h drug-light interval) or 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH) (4 mg·m-2 ;48 h) with wavelengths of 630 nm to 60J·cm-2 and 665 nm to 15-45J·cm-2 , respectively. With a median age of 69 years, patients were predominantly male (90%) with epithelioid histology (100%) and stage III-IV disease (100%). PT was delivered to a median of 55.0 CGE/1.8-2.0 CGE (range 50-75 CGE) adjuvantly (n = 8) or as salvage therapy (n = 2) following extended pleurectomy/decortication (ePD)/PDT. Two-year local control was 90%, with distant and regional failure rates of 50% and 30%, respectively. All patients received chemotherapy, and four received immunotherapy. Surgical complications included atrial fibrillation (n = 3), pneumonia (n = 2), and deep vein thrombosis (n = 2). Median survival from PT completion was 19.5 months (30.3 months from diagnosis), and 1- and 2-year survival rates were 58% and 29%. No patient experienced CTCAEv4 grade ≥2 acute or late toxicity. Our prolonged survival in very advanced-stage patients compares favorably to survival for PT without PDT and photon therapy with PDT, suggesting possible spatial or systemic cooperativity and immune effect.

Preoperative contralateral lung radiation dose is associated with postoperative pulmonary toxicity in patients with locally advanced non-small cell lung cancer treated with trimodality therapy

PURPOSE

In patients with non-small cell lung cancer (NSCLC) who undergo trimodality therapy (chemoradiation followed by surgical resection), it is unknown whether limiting preoperative radiation dose to the uninvolved lung reduces postsurgical morbidity. This study evaluated whether radiation fall-off dose parameters to the contralateral lung that is unaffected by NSCLC are associated with postoperative complications in NSCLC patients treated with trimodality therapy.

METHODS AND MATERIALS

We retrospectively reviewed NSCLC patients who underwent trimodality therapy between March 2008 and October 2016, with available restored digital radiation plans. Fischer's exact test was used to assess associations between patient and treatment characteristics and the development of treatment-related toxicity. Spearman rank correlation was used to measure the strength of association between dosimetric parameters.

RESULTS

Forty-six patients were identified who received trimodality therapy with intensity modulated radiation (median, 59.4 Gy; range, 45-70) and concurrent platinum doublet chemotherapy, followed by surgical resection. The median age was 64.9 years (range, 45.6-81.6). The median follow-up time was 1.9 years (range, 0.3-8.4). Twenty-four (52.2%) patients developed any-grade pulmonary toxicity and 14 (30.4%) patients developed grade 2+ pulmonary toxicity. There was an increased incidence of any-grade pulmonary toxicity in patients with contralateral lung volume receiving at least 20 Gy (V20) ≥7% compared with <7% (90%, n = 9 vs 41.7%, n = 15; P = .01). Similarly, contralateral lung V10 ≥20% was associated with an increased rate of any-grade pulmonary toxicity compared with V10 <20% (80%, n = 12 vs 38.7%, n = 12; P = .01). Pneumonectomy/bilobectomy was associated with grade 2+ pulmonary toxicity (P = .04).

CONCLUSIONS

Patients who received a higher radiation fall-off dose volume parameter (V20 ≥7% and V10 ≥20%) to the contralateral uninvolved lung had a higher incidence of any-grade postoperative pulmonary toxicity. Limiting radiation fall-off dose to the uninvolved lung may be an important modifiable radiation parameter in limiting postoperative toxicity in trimodality patients.

Utilization of Intensity-Modulated Radiation Therapy for Malignant Pleural Mesothelioma in the United States

BACKGROUND

Although postoperative radiotherapy (RT) for malignant pleural mesothelioma (MPM) has historically been delivered using 3-dimensional conformal RT (3DCRT) techniques, multiple reports show noteworthy safety and efficacy of the more advanced intensity-modulated RT (IMRT). To our knowledge, this is the only known study to evaluate national practice patterns of IMRT utilization for MPM.

MATERIALS AND METHODS

The National Cancer Data Base was queried for newly-diagnosed MPM patients who underwent definitive surgery (extrapleural pneumonectomy [EPP] or extended pleurectomy/decortication [P/D]) followed by adjuvant RT. Patients with metastatic disease, non-EPP or P/D surgical techniques, and lack of RT receipt (or without specified RT technique) were excluded. Statistics included multivariable logistic regression, Kaplan-Meier overall survival (OS) analysis, and Cox proportional hazards modeling.

RESULTS

Overall, 286 patients met criteria (181 [63%] IMRT and 105 [37%] 3DCRT). Temporal trends revealed that although 3DCRT was more common at initial time periods, IMRT utilization rose from 2004 to 2007 and stayed as a relatively constant majority thereafter. This was also present when substratifying the cohort according to EPP versus P/D approaches. IMRT was more often delivered at academic centers, along with institutions in the Southern United States, whereas 3DCRT was more frequently utilized in community facilities and in the Northeast (P ≤ .05 for all). RT technique did not affect OS (P > .05 for all comparisons).

CONCLUSION

In the United States, IMRT is now the most commonly utilized adjuvant RT technique for MPM. Facility and regional differences might associate with IMRT delivery. The findings of this investigation have implications for insurance coverage, clinical referral patterns, and ongoing and future prospective trial design.

Proton beam therapy for malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare disease with a poor prognosis. Surgical techniques have made incremental improvements over the last few decades while new systemic therapies, including immunotherapies, show promise as potentially effective novel therapies. Radiation therapy has historically been used only in the palliative setting or as adjuvant therapy after extrapleural pneumonectomy, but recent advances in treatment planning and delivery techniques utilizing intensity-modulated radiation therapy and more recently pencil-beam scanning (PBS) proton therapy, have enabled the delivery of radiation therapy as neoadjuvant or adjuvant therapy after an extended pleurectomy and decortication or as definitive therapy for patients with recurrent or unresectable disease. In particular, PBS proton therapy has the potential to deliver high doses of irradiation to the entire effected pleura while significantly reducing doses to nearby organs at risk. This article describes the evolution of radiation therapy for MPM and details how whole-pleural PBS proton therapy is delivered to patients at the Maryland Proton Treatment Center.

Treatment of Malignant Pleural Mesothelioma: American Society of Clinical Oncology Clinical Practice Guideline

Purpose To provide evidence-based recommendations to practicing physicians and others on the management of malignant pleural mesothelioma. Methods ASCO convened an Expert Panel of medical oncology, thoracic surgery, radiation oncology, pulmonary, pathology, imaging, and advocacy experts to conduct a literature search, which included systematic reviews, meta-analyses, randomized controlled trials, and prospective and retrospective comparative observational studies published from 1990 through 2017. Outcomes of interest included survival, disease-free or recurrence-free survival, and quality of life. Expert Panel members used available evidence and informal consensus to develop evidence-based guideline recommendations. Results The literature search identified 222 relevant studies to inform the evidence base for this guideline. Recommendations Evidence-based recommendations were developed for diagnosis, staging, chemotherapy, surgical cytoreduction, radiation therapy, and multimodality therapy in patients with malignant pleural mesothelioma. Additional information is available at www.asco.org/thoracic-cancer-guidelines and www.asco.org/guidelineswiki .

Radiotherapy for the treatment of malignant pleural mesothelioma

Malignant pleural mesothelioma is an aggressive disease that continues to be associated with poor outcomes. Although, traditionally this disease is considered to be resistant to radiotherapy, more recent evidence suggests that radiotherapy can produce positive outcomes. Over the past 15 years, the development of new, highly conformal radiotherapy techniques, such as intensity-modulated radiation therapy (IMRT), has enabled investigators to optimise the delivery of high-dose radiotherapy to the whole of the hemithorax. Prospective single-arm trials have shown that the median survival of patients who have completed high-dose hemithoracic radiotherapy after extrapleural pneumonectomy could reach 23·9-39·4 months independent of the chemotherapeutic response, suggesting that IMRT could potentially have an intrinsic benefit to this subset of patients. These observations have led to a change in practice, with the introduction of adjuvant pleural IMRT after pleurectomy-decortication and the development of induction-accelerated hemithoracic IMRT followed by extrapleural pneumonectomy. This Review focuses on recent observations on the role of radiotherapy in the treatment of malignant pleural mesothelioma, with particular emphasis on the results of clinical trials that evaluate the role of high-dose hemithoracic radiotherapy.

Proton Therapy for Malignant Pleural Mesothelioma: A Three Case Series Describing the Clinical and Dosimetric Advantages of Proton-Based Therapy

Malignant pleural mesothelioma (MPM) is a malignancy of the pleural cavity that typically presents at an advanced stage. Due to its large, circumferential clinical target volume (CTV) and proximity to major structures, including the heart and contralateral lung, delivering hemithoracic intensity-modulated radiotherapy (IMRT) with photon therapy to achieve loco-regional control following macroscopic complete resection is challenging. Intensity-modulated proton therapy (IMPT) has been shown to be a method for achieving higher therapeutic doses while limiting exposure to organs at risk (OARs), but patient outcomes after treatment have yet to be reported. We present three patients who received IMPT to 54 Gy after extrapleural pneumonectomy (EPP), with two patients receiving boosts to 66 and 60 Gy. All three tolerated treatment well and received doses to OARs markedly lower than those seen in comparison volumetric-modulated arc therapy (VMAT) IMRT photon plans. Radiation pneumonitis, a highly morbid and potentially fatal toxicity in patients receiving thoracic radiotherapy, was not observed even with boost treatments. In practice, IMPT appears to match dosimetric predictions as a feasible and safer alternative to photon IMRT-based radiotherapy. 

The role of radical radiotherapy in the management of malignant pleural mesothelioma: A systematic review

Malignant pleural mesothelioma (MPM) is a devastating disease with limited treatment options and a dismal prognosis. Attempts to employ radical radiotherapy in this disease have been limited by the complex shape of the pleura and the dose restrictions necessitated by the close proximity of radiosensitive structures. Recent shifts towards a 'lung sparing' surgical approach in MPM have further heightened these challenges. The aim of this systematic review is to assess recent advances in radiotherapy planning and delivery, to ascertain how these developments have impacted on the feasibility of delivering photon-based, high-dose radiotherapy with radical intent in MPM. Three electronic databases were searched and a total of 249 articles reviewed. The challenge of generating high quality, practice-defining data for diseases such as MPM was highlighted by the identification of just two randomised studies. Much of the literature consisted of low quality, retrospective data with small cohorts and inconsistent reporting on radiotherapy techniques and dosimetry. Nevertheless, a number of prospective phase II studies were identified to suggest that radical doses of radiotherapy can be delivered safely after a lung sparing procedure in MPM, reporting encouraging survival data and acceptable levels of toxicity.

Malignant pleural mesothelioma - Pleural cavity irradiation after decortication with helical tomotherapy

BACKGROUND

Malignant pleural mesothelioma (MPM) is a rare and aggressive disease that poses a treatment challenge in spite of recent technical developments. The aim of this retrospective analysis is to assess the feasibility of administering intensity-modulated radiotherapy (IMRT) to the pleural cavity using helical tomotherapy in patients who had undergone pleurectomy/decortication (P/D) and also the resulting toxicity levels.

PATIENTS AND METHODS

Ten patients who had MPM and had undergone P/D were treated with pleural cavity irradiation that included a median dose of 52.2 Gy using helical tomotherapy. The median age of the patients was 53 years (31-74). In addition to clinical and diagnostic findings from regular follow-up examinations, we evaluated the dose distribution for other organs at risk to assess treatment in relation to toxicity, with special regard for the underlying intact lung.

RESULTS

The mean lung dose on the treatment site was 32.8 Gy (±6.8). The V_20 Gy was 71.7% (±17.2). No treatment-related toxicity that exceeded grade III according to common toxicity criteria (CTC) was observed. Median progression-free survival (PFS) was 13 months with a median overall survival (OAS) of 19 months.

CONCLUSION

The findings of this analysis provide data indicating that sparing the underlying lung in patients with MPM after P/D is not only feasible with helical tomotherapy, but that this treatment also causes reasonably few side effects.

Long-term outcomes of intensity-modulated radiotherapy following extra-pleural pneumonectomy for malignant pleural mesothelioma

BACKGROUND

The purpose was to evaluate safety and efficacy of intensity-modulated radiotherapy (IMRT) following extra-pleural pneumonectomy (EPP) for malignant pleural mesothelioma (MPM).

MATERIAL AND METHODS

Patients with MPM of clinical stage I-III, which were macroscopic completely resected with EPP were eligible for this prospective study. The ipsilateral hemithorax was irradiated with a prescribed dose of 50.4 Gy. When the high-risk surgical margins or FDG-avid regions were identified, simultaneous integrated boost (SIB) with 56.0 Gy or 61.6 Gy was applied.

RESULTS

Twenty-one patients were enrolled. SIB was applied to five patients. The planned IMRT fractions were completed in all, but four patients who suffered from severe fatigue or radiation pneumonitis. With a potential median follow-up of 6.3 years, overall survival was 37.5% at 3 years since the IMRT. The median survival time was 17.5 and 27.0 months since the IMRT and the initial treatment, respectively. Three patients have survived for more than 5 years. Distant metastasis was observed in 15 patients. Local recurrence was also observed in 2 of the 15 patients. Acute toxicities of Grade 3 or worse were observed in 15 patients, including 9 with hematological, 3 with pneumonitis and 6 with fatigue, nausea or vomiting. Five patients developed Grade 3 or worse late toxicities associated with IMRT, consisting of one with persistent Grade 4 thrombocytopenia, one with brain infarction and congestive liver dysfunction, and three with elevation of serum transaminase or biliary enzyme. No Grade 5 toxicity was observed. Patients with N2 showed significantly worse survival than those with N0-1 (18.2% vs. 60.0% at 3 years, p = .014).

CONCLUSION

IMRT following EPP achieved excellent local control for MPM, that might lead to the long-term survival in selected patients. However, treatment burden including acute and late toxicities should be considered in this treatment approach.

Malignant pleural mesothelioma: adjuvant therapy with radiation therapy

It is a challenge to treat malignant pleural mesothelioma with radiation therapy (RT). For many years, conventional RT was delivered after extrapleural pneumonectomy (EPP) with acceptable results. However, the benefit of RT has never been definitively proven. Intensity modulated radiation therapy (IMRT) has been used, but some of the early experiences revealed fatal toxicity. As experience has increased, it now appears that RT, particularly with IMRT, is both feasible and effective.

Heart Dosimetry is Correlated With Risk of Radiation Pneumonitis After Lung-Sparing Hemithoracic Pleural Intensity Modulated Radiation Therapy for Malignant Pleural Mesothelioma

PURPOSE

To determine clinically helpful dose-volume and clinical metrics correlating with symptomatic radiation pneumonitis (RP) in malignant pleural mesothelioma (MPM) patients with 2 lungs treated with hemithoracic intensity modulated pleural radiation therapy (IMPRINT).

METHODS AND MATERIALS

Treatment plans and resulting normal organ dose-volume histograms of 103 consecutive MPM patients treated with IMPRINT (February 2005 to January 2015) to the highest dose ≤50.4 Gy satisfying departmental normal tissue constraints were uniformly recalculated. Patient records provided maximum RP grade (Common Terminology Criteria for Toxicity and Adverse Event version 4.0) and clinical and demographic information. Correlations analyzed with the Cox model were grade ≥2 RP (RP2+) and grade ≥3 RP (RP3+) with clinical variables, with volumes of planning target volume (PTV) and PTV-lung overlap and with mean dose, percent volume receiving dose D (V_D), highest dose encompassing % volume V, (D_V), and heart, total, ipsilateral, and contralateral lung volumes.

RESULTS

Twenty-seven patients had RP2+ (14 with RP3+). The median prescription dose was 46.8 Gy (39.6-50.4 Gy, 1.8 Gy/fraction). The median age was 67.6 years (range, 42-83 years). There were 79 men, 40 never-smokers, and 44 with left-sided MPM. There were no significant (P≤.05) correlations with clinical variables, prescription dose, total lung dose-volume metrics, and PTV-lung overlap volume. Dose-volume correlations for heart were RP2+ with V_D (35 ≤ D ≤ 47 Gy, V₄₃ strongest at P=.003), RP3+ with V_D (31 ≤ D ≤ 45 Gy), RP2+ with D_V (5 ≤ V ≤ 30%), RP3+ with D_V (15 ≤ V ≤ 35%), and mean dose. Significant for ipsilateral lung were RP2+ with V_D (38 ≤ D ≤ 44 Gy), RP3+ with V₄₁, RP2+ and RP3+ with minimum dose, and for contralateral lung, RP2+ with maximum dose. Correlation of PTV with RP2+ was strong (P<.001) and also significant with RP3+.

CONCLUSIONS

Heart dose correlated strongly with symptomatic RP in this large cohort of MPM patients with 2 lungs treated with IMPRINT. Planning constraints to reduce future heart doses are suggested.

Geometric dose prediction model for hemithoracic intensity-modulated radiation therapy in mesothelioma patients with two intact lungs

The presence of two intact lungs makes it challenging to reach a tumoricidal dose with hemithoracic pleural intensity-modulated radiation therapy (IMRT) in patients with malignant pleural mesothelioma (MPM) who underwent pleurectomy/decortications or have unresectable disease. We developed an anatomy-based model to predict attainable prescription dose before starting optimization. Fifty-six clinically delivered IMRT plans were analyzed regarding correlation of prescription dose and individual and total lung volumes, planning target volume (PTV), ipsilateral normal lung volume and ratios: contralateral/ipsilateral lung (CIVR); contralateral lung/PTV (CPVR); ipsilateral lung /PTV (IPVR); ipsilateral normal lung /total lung (INTLVR); ipsilateral normal lung/PTV (INLPVR). Spearman's rank correlation and Fisher's exact test were used. Correlation between mean ipsilateral lung dose (MILD) and these volume ratios and between prescription dose and single lung mean doses were studied. The prediction models were validated in 23 subsequent MPM patients. CIVR showed the strongest correlation with dose (R=0.603,p<0.001) and accurately predicted prescription dose in the validation cases. INLPVR and MILD as well as MILD and prescription dose were significantly correlated (R=-0.784,p<0.001 and R=0.554,p<0.001, respectively) in the training and validation cases. Parameters obtainable directly from planning scan anatomy predict achievable prescription doses for hemithoracic IMRT treatment of MPM patients with two intact lungs. PACS number(s): 87.55.de, 87.55.dk.

Intensity modulated radiation therapy after extra-pleural pneumonectomy for malignant pleural mesothelioma is feasible without fatal pulmonary toxicity and provides good survival

AIM

To analyze patterns of failure, toxicity, relapse-free survival (RFS), and overall survival (OS) in malignant pleural mesothelioma (MPM) patients treated with intensity-modulated radiation therapy following extrapleural pneumonectomy (EPP).

METHODS

We reviewed 18 charts of patients with MPM from 2005 to 2014 who underwent EPP followed by hemithoracic intensity-modulated radiation therapy. Intensity-modulated radiation therapy dose delivery adhered to published lung dose constraints. Kaplan-Meier curves were used to assess the RFS and OS. Median survival times are reported for both RFS and OS.

RESULTS

Median age was 65 years (range: 40-76 years). Chemotherapy was administered in four neo-adjuvant and seven adjuvant patients. Pathological American Joint Committee on Cancer stages II, III, IV, surgical margin, lympho-vascular space, pericardium, and chest wall involvement were seen in 3, 12, 3, 9, 7, 12 and 3 patients, respectively. The majority of the patients received 45 Gy in 25 fractions. The mean lung dose was 7.14 Gy (range: 5 Gy-9.3 Gy). The mean V20 was 2.23%. At a median follow-up of 3 years, eight patients were alive (44%); 10 experienced relapse (56%). Median RFS and OS were 24.4 months (95% CI: >16.3 months) and 38.2 months (95% CI: 17.4-78.1 months), respectively. Acute toxicities were fatigue, dermatitis, nausea, esophagitis/dysphagia, cough, and dyspnea on exertion. No grade III, IV, or fatal pulmonary toxicities were observed.

CONCLUSION

Intensity-modulated radiation therapy following EPP for MPM resulted in RFS and OS comparable to the published literature without significant toxicity.

Intensity-Modulated Radiation Therapy Improves the Target Coverage Over 3-D Planning While Meeting Lung Tolerance Doses for All Patients With Malignant Pleural Mesothelioma

PURPOSE

To investigate high conformality on target coverage and the ability on creating strict lung dose limitation of intensity-modulated radiation therapy in malignant pleural mesothelioma.

PATIENTS AND METHODS

Twenty-four radiation therapy plannings were evaluated and compared with dosimetric outcomes of conformal radiation therapy and intensity-modulated radiation therapy. Hemithoracal radiation therapy was performed on 12 patients with a fraction of 1.8 Gy to a total dose of 50.4 Gy. All organs at risk were contoured. Radiotherapy plannings were differed according to the technique; conformal radiation therapy was planned with conventionally combined photon-electron fields, and intensity-modulated radiation therapy was planned with 7 to 9 radiation beam angles optimized in inverse planning. Strict dose-volume constraints were applied.

RESULTS

Intensity-modulated radiation therapy was statistically superior in target coverage and dose homogeneity (intensity-modulated radiation therapy-planning target volume 95 mean 100%; 3-dimensional conformal radiation therapy-planning target volume 95 mean 71.29%, P = .0001; intensity-modulated radiation therapy-planning target volume 105 mean 11.14%; 3-dimensional conformal radiation therapy-planning target volume 105 mean 35.69%, P = .001). The dosimetric results of the remaining lung was below the limitations on intensity-modulated radiation therapy planning data (intensity-modulated radiation therapy-lung mean dose mean 7.5 [range: 5.6%-8.5%]; intensity-modulated radiation therapy-lung V5 mean 55.55% [range: 47%-59.9%]; intensity-modulated radiation therapy-lung V20 mean 4.5% [range: 0.5%-9.5%]; intensity-modulated radiation therapy-lung V13 mean 13.43% [range: 4.2%-22.9%]).

CONCLUSION

With a complex and large target volume of malignant pleural mesothelioma, intensity-modulated radiation therapy has the ability to deliver efficient tumoricidal radiation dose within the safe dose limits of the remaining lung tissue.

Phase II Study of Hemithoracic Intensity-Modulated Pleural Radiation Therapy (IMPRINT) As Part of Lung-Sparing Multimodality Therapy in Patients With Malignant Pleural Mesothelioma

PURPOSE

We conducted a two-center phase II study to determine the safety of hemithoracic intensity-modulated pleural radiation therapy (IMPRINT) after chemotherapy and pleurectomy-decortication (P/D) as part of a multimodality lung-sparing treatment.

PATIENTS AND METHODS

Patients received up to four cycles of pemetrexed plus platinum. If feasible, P/D was performed. Hemithoracic IMPRINT was administered to a planned dose of 50.4 Gy in 28 fractions. The primary end point was the incidence of grade 3 or greater radiation pneumonitis (RP).

RESULTS

A total of 45 patients were enrolled; 18 were not evaluable (because of disease progression before radiation therapy [RT], n = 9; refusal of surgery or RT, n = 5; extrapleural pneumonectomy at time of surgery, n = 2; or chemotherapy complications, n = 2). A total of 26 patients received pemetrexed plus cisplatin, 18 received pemetrexed plus carboplatin, and four received a combination. Thirteen patients (28.9%) had a partial response, 15 patients (33.3%) experienced disease progression, one patient died during chemotherapy, and all others had stable disease. Eight patients underwent P/D or an extended P/D, and 13 underwent a partial P/D. A total of 27 patients started IMPRINT (median dose, 46.8 Gy; range, 28.8 to 50.4 Gy) and were evaluable for the primary end point (median follow-up, 21.6 months). Six patients experienced grade 2 RP, and two patients experienced grade 3 RP; all recovered after corticosteroid initiation. No grade 4 or 5 radiation-related toxicities were observed. The median progression-free survival and overall survival (OS) were 12.4 and 23.7 months, respectively; the 2-year OS was 59% in patients with resectable tumors and was 25% in patients with unresectable tumors.

CONCLUSIONS

Hemithoracic IMPRINT for malignant pleural mesothelioma (MPM) is safe and has an acceptable rate of RP. Its incorporation with chemotherapy and P/D forms a new lung-sparing treatment paradigm for patients with locally advanced MPM.

The Third Italian Consensus Conference for Malignant Pleural Mesothelioma: State of the art and recommendations

Malignant Pleural Mesothelioma (MPM) remains a relevant public health issue, and asbestos exposure is the most relevant risk factor. The incidence has considerably and constantly increased over the past two decades in the industrialized countries and is expected to peak in 2020-2025. In Italy, a standardized-rate incidence in 2011 among men was 3.5 and 1.25 per 100,000 in men and women, respectively, and wide differences are noted among different geographic areas. The disease remains challenging in terms of diagnosis, staging and treatment and an optimal strategy has not yet been clearly defined. The Third Italian Multidisciplinary Consensus Conference on Malignant Pleural Mesothelioma was held in Bari (Italy) in January 30-31, 2015. This Consensus has provided updated recommendations on the MPM management for health institutions, clinicians and patients.

Intensity-modulated radiotherapy for lung cancer: current status and future developments

Radiotherapy plays an important role in the management of lung cancer, with over 50% of patients receiving this modality at some point during their treatment. Intensity-modulated radiotherapy (IMRT) is a technique that adds fluence modulation to beam shaping, which improves radiotherapy dose conformity around the tumor and spares surrounding normal structures. Treatment with IMRT is becoming more widely available for the treatment of lung cancer, despite the paucity of high level evidence supporting the routine use of this more resource intense and complex technique. In this review article, we have summarized data from planning and clinical studies, discussed challenges in implementing IMRT, and made recommendations on the minimum requirements for safe delivery of IMRT.

Radiation therapy for malignant pleural mesothelioma

Malignant pleural mesothelioma is an aggressive tumor where the ability to control the primary tumor (local control) presents a significant challenge. External beam radiation has the potential to improve local control when following established safe and effective protocols. Radiation is primarily used as adjuvant treatment after extrapleural pneumonectomy or pleurectomy/decortication and as palliative treatment in some cases. The target volume for radiotherapy of malignant pleural mesothelioma can be quite extensive and thus toxicity is its chief limitation.

Stereotactic body radiation therapy for a new lung cancer arising after pneumonectomy: dosimetric evaluation and pulmonary toxicity

OBJECTIVE

To evaluate the tolerance of stereotactic body radiation therapy (SBRT) for the treatment of secondary lung tumours in patients who underwent previous pneumonectomy.

METHODS

12 patients were retrospectively analysed. The median maximum tumour diameter was 2.1 cm (1-4.5 cm). The median planning target volume was 20.7 cm(3) (2.4-101.2 cm(3)). Five patients were treated with a single fraction of 26 Gy and seven patients with fractionated schemes (3 × 10 Gy, 4 × 10 Gy, 4 × 12 Gy). Lung toxicity, correlated with volume (V) of lung receiving >5, >10 and >20 Gy, local control and survival rate were assessed. Median follow-up was 28 months.

RESULTS

None of the patients experienced pulmonary toxicity > grade 2 at the median dosimetric lung parameters of V5, V10 and V20 of 23.1% (range 10.7-56.7%), 7.3% (2.2-27.2%) and 2.7% (0.7-10.9%), respectively. No patients required oxygen or had deterioration of the performance status during follow-up if not as a result of clinical progression of disease. The local control probability at 2 years was 64.5%, and the overall survival at 2 years was 80%.

CONCLUSION

SBRT appears to be a safe and effective modality for treating patients with a second lung tumour after pneumonectomy.

ADVANCES IN KNOWLEDGE

Our results and similar literature results show that when keeping V5, V10 V20 <50%, <20% and <7%, respectively, the risk of significant lung toxicity is acceptable. Our experience also shows that biologically effective dose 10 >100 Gy, necessary for high local control rate, can be reached while complying with the dose constraints for most patients.