Hemithoracic Radiotherapy After Extrapleural Pneumonectomy for Malignant Pleural Mesothelioma: A Dosimetric Comparison of Two Well-Described Techniques

Trimodality treatment in malignant pleural mesothelioma - Ordeal or real deal?

BACKGROUND

Management of MPM is complex and controversial as there is a paucity of good quality evidence. We report the toxicity and outcomes in patients who received trimodality treatment for non-metastatic MPM at our institution.

METHODS & MATERIALS

We reviewed the electronic medical records of surgically managed MPM patients at our institution in the last decade. Dosimetric parameters of target volume and organs at risk were documented by the treatment planning workstation. SPSS was used for statistical analysis.

RESULTS

Between January 2008 and October 2018, 21 patients underwent surgery for MPM - all but 2 patients underwent extra-pleural pneumonectomy (EPP); epithelioid MPM was the most common histology. All patients, except 2, received neoadjuvant Pemetrexed/platinum doublet chemotherapy. Fourteen patients received adjuvant hemithoracic RT; ten patients were treated with a conformal technique at our institute and dosimetric data was available for analysis. Average time to start RT after surgery was 51 days (range 32-82 days). All patients were treated with a conformal technique using IMRT/VMAT to a dose of 45Gy in 25 fractions. Mean overall RT duration was 35 days (range 30-42 days). Grade I/II Pneumonitis was seen in 4 patients. One patient developed grade III acute lung toxicity unrelated to RT. At a median follow up of 25 months, 8 patients had died, of whom six died due to the disease and two died in the immediate post op period. Two-year DFS and OS were 58% and 73%, respectively.

CONCLUSION

In spite of the extensive surgery and complex hemithoracic RT, we demonstrated excellent dosimetry, toxicity profile and favorable outcomes in non-metastatic MPM.

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.

Adjuvant, neoadjuvant, and definitive radiation therapy for malignant pleural mesothelioma

While ionizing radiotherapy (RT) can provide durable local control, the relative radiosensitivity of surrounding organs such as the lungs and heart and the distributed nature of the pleura limit the ability to safely deliver RT for patients with malignant pleural mesothelioma (MPM). Recent advances in the technological sophistication of RT planning and delivery devices have resulted in increased spatial control of irradiation dose that has extended the palliative and definitive applications of RT for patients with MPM. This review will outline the logistical, mechanistic and clinical basics of RT and the clinical trials supporting the use of RT in the multidisciplinary care of patients with MPM.

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.

Intensity-modulated radiotherapy after extrapleural pneumonectomy in the combined-modality treatment of malignant pleural mesothelioma

INTRODUCTION

Local therapy is becoming increasingly important as a part of the definitive treatment for malignant pleural mesothelioma after extrapleural pneumonectomy (EPP) because of the emergence of trimodality therapy consisted of chemotherapy, EPP, and adjuvant radiotherapy. Herein, we explore the current evidence and indications for adjuvant intensity-modulated radiotherapy (IMRT), as well as how to further improve this technique and adapt new technology in the delivering adjuvant radiotherapy in the setting of trimodality therapy.

METHODS

A systematic review of relevant studies identified through PubMed, ISI Web of Knowledge (Web of Science), the Cochrane Library, and the National Guideline Clearinghouse search engines was performed.

RESULTS

Local control remains poor despite the inclusion of conventional adjuvant radiation therapy in trimodality therapy. This can be improved by the delivery of adjuvant IMRT. However, IMRT can be associated with severe pulmonary toxicity if the radiation dose to the remaining lung is not kept to a very low level. This is especially true when patients are receiving chemotherapy. New advances in technology can allow for lower doses to the contralateral lung, decreased treatment delivery time, and improved target dose coverage.

CONCLUSION

Excellent local control can be achieved through adjuvant IMRT after EPP for malignant pleural mesothelioma. Severe pulmonary toxicity may be avoided by setting stringent dose constraints for the contralateral lung. This can be aided by the advances in technology. Post-treatment surveillance may be reliably conducted by periodical [18F]-fluorodeoxyglucose-positron emission tomography imaging.

What is the role of radiotherapy in malignant pleural mesothelioma?

OBJECTIVE

A review of the evidence supporting the use of radiotherapy in patients with mesothelioma was performed.

METHODS

Relevant publications were searched for on Medline.

RESULTS

In a Medline search on radiotherapy and mesothelioma, 611 hits were obtained. A limited number of prospective phase II trials of radiotherapy as part of trimodality protocols for early disease and in the palliation of pain were found, along with three small randomized controlled trials of port-site prophylaxis.

CONCLUSION

No randomized data exist to support the use of radiotherapy after radical surgery, although there are a large number of publications describing its use as an integral part of therapy, including seven phase II studies. One ongoing trial is randomizing patients to radiotherapy or not after extrapleural pneumonectomy. None of these studies provided any assessment of radiotherapy independent of the other modalities investigated, nor did any formally assess intensity-modulated radiotherapy. There have been several reports of excessive toxicity with this technique, and its use should be limited to phase I studies until the basis of this toxicity is better understood. Three trials have looked at port-site prophylaxis, one supporting its use and two showing no evidence of benefit. Two studies addressed pain control prospectively, one showing definite but short-lived benefits. Implications. Radiotherapy is widely used in treating mesothelioma with little supporting evidence. More randomized trials are required to justify this use in all three common settings for its use.