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

Safety and efficacy of helical tomotherapy following lung-sparing surgery in locally advanced malignant pleural mesothelioma

PURPOSE

To assess the value of radiation therapy (RT) with helical tomotherapy (HT) in the management of locally advanced malignant pleural mesothelioma (MPM) receiving no or lung-sparing surgery.

METHODS

Consecutive MPM cases not undergoing extrapleural pneumonectomy and receiving intensity-modulated (IM) HT were retrospectively evaluated for local control, distant control, progression-free survival (PFS), and overall survival (OS). Impact of age, systemic treatment, RT dose, and recurrence patterns was analyzed by univariate and multivariate analysis. As a secondary endpoint, reported toxicity was assessed.

RESULTS

A total of 34 localized MPM cases undergoing IMHT were identified, of which follow-up data were available for 31 patients. Grade 3 side effects were experienced by 26.7% of patients and there were no grade 4 or 5 events observed. Median PFS was 19 months. Median OS was 20 months and the rates for 1‑ and 2‑year OS were 86.2 and 41.4%, respectively. OS was significantly superior for patients receiving adjuvant chemotherapy (p = 0.008).

CONCLUSION

IMHT of locally advanced MPM after lung-sparing surgery is safe and feasible, resulting in satisfactory local control and survival. Adjuvant chemotherapy significantly improves OS. Randomized clinical trials incorporating modern RT techniques as a component of trimodal treatment are warranted to establish an evidence-based standard of care pattern for locally advanced MPM.

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.

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.

Immune checkpoint inhibitors for unresectable malignant pleural mesothelioma

Unresectable malignant pleural mesothelioma (MPM) is an aggressive disease with a 5-year survival rate of approximately 10%. Recent data suggest that MPM is an immunologically active tumor, in which checkpoint inhibition through the blockade of the anti-cytotoxic T lymphocyte antigen-4 (-CTLA-4) or anti-programmed cell death 1 (PD-1) could play a major therapeutic role. Initially, clinical trials evaluated immune checkpoint inhibitors (ICIs) in the salvage setting after platinum-based chemotherapy with mixed results in terms of efficacy. More recently, the combination of the anti-CTLA-4 agent ipilimumab plus the anti-PD-1 agent nivolumab was tested in the front-line setting, and reported a superior survival as compared to platinum/pemetrexed. While other clinical trials ore ongoing in order to investigate ICIs for MPM, it seems now evident that we have entered a new "era" for the treatment of MPM. In the future, a few issues need to be solved with regard to the use of ICIs for MPM. Among them, there is the identification of biomarkers of sensitivity to immunotherapy that may help enrich the patient population who could benefit the most from treatment, while avoiding for some other patients the potential occurrence of immune-related side effects from therapies that are anticipated to be ineffective.

Quantitation and predictors of short-term mortality following extrapleural pneumonectomy, pleurectomy/decortication, and nonoperative management for malignant pleural mesothelioma

Background

For malignant pleural mesothelioma (MPM), the benefit of resection, as well as the optimal surgical technique, remain controversial. In efforts to better refine patient selection, this retrospective observational cohort study queried the National Cancer Database in an effort to quantify and evaluate predictors of 30- and 90-day mortality between extrapleural pneumonectomy (EPP) and pleurectomy/decortication (P/D), as well as nonoperative management.

Methods

After applying selection criteria, cumulative incidences of mortality by treatment paradigm were graphed for the unadjusted and propensity-matched populations, as well as for six a priori age-based intervals (≤60, 61–65, 66–70, 71–75, 76–80, and ≥81 years). The interaction between age and hazard ratio (HR) for mortality between treatment paradigms was also graphed. Cox multivariable analysis ascertained factors independently associated with 30- and 90-day mortality.

Results

Of 10,723 patients, 2,125 (19.8%) received resection (n=438 EPP, n=1,687 P/D) and 8,598 (80.2%) underwent nonoperative management. The unadjusted 30/90-day mortality for EPP, P/D, and all operated cases was 3.0%/8.0%, 5.4%/14.1%, and 4.9%/12.8%, respectively. There were no short-term mortality differences between EPP and P/D following propensity-matching, within each age interval, or between age subgroups on interaction testing (P>0.05 for all). Nonoperative patients had a crude 30- and 90-day mortality of 9.9% and 24.6%, respectively. Several variables were identified as predictors of short-term mortality, notably patient age (HR 1.022, P<0.001), Charlson-Deyo comorbidity index (HR 1.882, P<0.001), receipt of treatment at high-volume centers (HR 0.834, P=0.032) and induction chemotherapy (HR 1.735, P=0.025), among others. The patient (yearly) incremental increase in age conferred 2.0% (30 day) and 2.2% (90 day) increased risk of mortality (P<0.001).

Conclusions

Quantitative estimates of age-associated 30- and 90-day mortality of EPP and P/D should be considered when potentially operable patients are counseled regarding the risks and benefits of resection.

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.

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.

Impact of Detecting Occult Pathologic Nodal Disease During Resection for Malignant Pleural Mesothelioma

BACKGROUND

Lymph node (LN) involvement is a poor prognostic factor for malignant pleural mesothelioma (MPM). However, to our knowledge, postresection outcomes of node-negative (cN0/pN0), occult pathologic nodal disease (cN0/pN+), and clinical node-positive disease (cN+) have not been compared to date.

PATIENTS AND METHODS

The National Cancer Data Base was queried for newly diagnosed, resected MPM with known clinical/pathologic LN information. Three cohorts were compared: cN0/pN0, cN+, and cN0/pN+. Multivariable logistic regression examined predictors of pathologic nodal upstaging. Kaplan-Meier analysis with propensity matching assessed overall survival (OS); multivariate Cox proportional hazards modeling examined predictors thereof.

RESULTS

Of 1369 patients, 687 (50%) had cN0/pN0, 457 (33%) cN+, and 225 (16%) cN0/pN+ disease. Median follow-up was 29 months. In patients with cN0 disease, factors associated with pathologic nodal upstaging were younger age, greater number of examined LNs, and nonsarcomatoid histology (P < .05 for all). Relative to pN0 cases, occult LN involvement (65% being pN2) was associated with 51% higher hazard of mortality on multivariate analysis (P = .005). Following propensity matching, the OS of cN0/pN+ was similar to cN+ cases (P = .281). On multivariate analysis, the number of involved LNs (continuous variable, P = .013), but not nodal tumor, node, metastasis (TNM) classification or LN ratio (P > .05 for both), was associated with OS.

CONCLUSION

Detecting occult nodal disease during resection for cN0 MPM is associated with poorer prognosis, with similar survival as cN+ cases, underscoring the importance of routine preoperative pathologic nodal assessment for potentially resectable MPM. The number of involved LNs (rather than current location-based classification) may provide more robust prognostic stratification for future TNM staging.

Patterns of Care and Outcomes of Elderly Esophageal Cancer Patients Not Meeting Age-based Criteria of the CROSS Trial

OBJECTIVES

The CROSS trial established neoadjuvant chemoradiation followed by surgery (nCRT-S) as superior to surgery alone (S) for locally advanced esophageal cancer (EC). However, because patients above 75 years of age were excluded, this comparison cannot be extrapolated to older patients. This study of a large, contemporary national database evaluated practice patterns in elderly patients ineligible for CROSS, and analyzed overall survival (OS) between nCRT+S, S, and definitive CRT (dCRT).

MATERIALS AND METHODS

The National Cancer Data Base was queried for EC patients with cT1N1M0/T2-3N0-1M0 EC (per the CROSS trial) but 76 years and above of age. Multivariable logistic regression ascertained factors associated with nCRT+S (vs. S). Kaplan-Meier analysis evaluated OS; Cox multivariate analysis determined variables associated with OS. Propensity matching aimed to address group imbalances and indication biases.

RESULTS

Of 4099 total patients, 594 (14%) underwent nCRT+S, 494 (12%) underwent S, and 3011 (73%) underwent dCRT. Since 2010, trimodality management has risen, corresponding to declines in S and dCRT. Median OS in the respective groups were 26.7, 20.3, and 17.8 months (P<0.05). Following propensity matching, there was a trend towards higher OS with nCRT-S over S (P=0.077); dCRT showed poorer OS than nCRT-S (P<0.001) but was equivalent to S (P=0.669). Before and following matching, nCRT-S experienced equivalent 30- and 90-day mortality as S (P>0.05), with lower 30-day readmission and postoperative hospital stay (P<0.05).

CONCLUSIONS

Although most older patients not meeting CROSS criteria undergo dCRT, utilization of trimodality therapy is rising. Despite the trend towards higher OS with trimodality therapy without poorer postoperative outcomes, careful patient selection continues to be essential in this population.

Physician And Patient Barriers To Radiotherapy Service Access: Treatment Referral Implications

Radiotherapy is one of the mainstays of cancer treatment, and about 60% of cancer patients receive this type of treatment during their course of treatment. An evident gap between optimal and actual radiotherapy utilization proportions has recently been reported, which has been ascribed to lack of referral to radiation oncology. There are many factors influencing the radiotherapy referral, including patient anxiety about toxicity, wrong perception of efficacy and side effects by physicians and patients, insufficient knowledge of referral process. These factors, defined as barriers can be categorized in health system barriers, physician and patient barriers. In the present brief narrative review, we discussed barriers to radiotherapy referral focusing on physician and patient barriers.

The role of radiation treatment in pleural mesothelioma: Highlights of the 14th International Conference of the International mesothelioma interest group

Radiation remains an important component of mesothelioma treatment in 2018. Its use as a treatment modality continues to evolve as the technology for planning and delivery continues to improve. Use of radiation to improve local control in the involved hemithorax has been a common adjuvant treatment post extrapleural pneumonectomy for many years. Modern treatment options with advanced planning techniques including protons and intensity modulated radiation therapy lead to new potential options for treatment post lung-sparing surgery or in the unresectable setting. Presentations and discussions on the implementation of these strategies for palliation, treatment of oligometastatic recurrence or unresectable disease were the focus of a session dedicated to the role of radiation therapy at the 14^th International Conference of the International Mesothelioma Interest Group and are reviewed in this article. Preclinical data to better understand how to integrate radiation and the delivery of novel systemic therapy approached like check point inhibitors are also presented.

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.