Establishing locoregional control of malignant pleural mesothelioma using high-dose radiotherapy and 18F-FDG PET/CT scan correlation

Response Evaluation Following Radiation Therapy With 18F-FDG PET/CT: Common Variants of Radiation-Induced Changes and Potential Pitfalls

Radiation therapy (RT) is one of the cornerstones in cancer treatment and approximately half of all patients will receive some form of RT during the course of their cancer management. Response evaluation after RT and follow-up imaging with ¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) can be complicated by RT-induced acute, chronic or consequential effects. There is a general consensus that ¹⁸F-FDG PET/CT for response evaluation should be delayed for 12 weeks after completing RT to minimize the risk of false-positive findings. Radiation-induced late side effects in normal tissue can take years to develop and eventually cause symptoms that on imaging can potentially mimic recurrent disease. Imaging findings in radiation induced injuries depend on the normal tissue included in the irradiated volume and the radiation therapy regime including the total dose delivered, dose per fraction and treatment schedule. The intent for radiation therapy should be taken in consideration when evaluating the response on imaging, that is palliative vs curative or neoadjuvant vs adjuvant RT. Imaging findings can further be distorted by altered anatomy and sequelae following surgery within the radiation field. An awareness of common PET/CT-induced changes/injuries is essential when interpreting ¹⁸F-FDG PET/CT as well as obtaining a complete medical history, as patients are occasionally scanned for an unrelated cause to previously RT treated malignancy. In addition, secondary malignancies due to carcinogenic effects of radiation exposure in long-term cancer survivors should not be overlooked. ¹⁸F-FDG PET/CT can be very useful in response evaluation and follow-up in patients treated with RT, however, variants and pitfalls are common and it is important to remember that radiation-induced injury is often a diagnosis of exclusion.

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.

The Use of Radiation Therapy for the Treatment of Malignant Pleural Mesothelioma: Expert Opinion from the National Cancer Institute Thoracic Malignancy Steering Committee, International Association for the Study of Lung Cancer, and Mesothelioma Applied Research Foundation

INTRODUCTION

Detailed guidelines regarding the use of radiation therapy for malignant pleural mesothelioma (MPM) are currently lacking because of the rarity of the disease, the wide spectrum of clinical presentations, and the paucity of high-level data on individual treatment approaches.

METHODS

In March 2017, a multidisciplinary meeting of mesothelioma experts was cosponsored by the U.S. National Cancer Institute, International Association for the Study of Lung Cancer Research, and Mesothelioma Applied Research Foundation. Among the outcomes of this conference was the foundation of detailed, multidisciplinary consensus guidelines.

RESULTS

Here we present consensus recommendations on the use of radiation therapy for MPM in three discrete scenarios: (1) hemithoracic radiation therapy to be used before or after extrapleural pneumonectomy; (2) hemithoracic radiation to be used as an adjuvant to lung-sparing procedures (i.e., without pneumonectomy); and (3) palliative radiation therapy for focal symptoms caused by the disease. We discuss appropriate simulation techniques, treatment volumes, dose fractionation regimens, and normal tissue constraints. We also assess the role of particle beam therapy, specifically, proton beam therapy, for MPM.

CONCLUSION

The recommendations provided in this consensus statement should serve as important guidelines for developing future clinical trials of treatment approaches for MPM.

Computed tomography features of local pleural recurrence in patients with malignant pleural mesothelioma treated with intensity-modulated pleural radiation therapy

OBJECTIVE

This study was conducted in order to describe the computed tomography (CT) features of local pleural recurrence in patients with malignant pleural mesothelioma undergoing intensity-modulated pleural radiation therapy (IMPRINT) as part of multimodality treatment.

METHODS

In this observational study, 58 patients treated with IMPRINT between September 21, 2004, and December 1, 2014 were included. Baseline and follow-up CT scans were qualitatively assessed. On follow-up scans, pleural thickening was categorized as unchanged, decreased, or new/increased. New/increased pleural abnormality was subcategorized as diffuse smooth pleural thickening, diffuse nodular pleural thickening, focal pleural nodule, or multiple pleural nodules. To identify features more frequently present at the time of local recurrence, follow-up scans with local recurrence were matched to four control scans; exact conditional logistic regression was performed.

RESULTS

Twenty-one (36%) patients had local pleural recurrence and 20 (34%) patients had nonpleural recurrence; 3 patients had both types of recurrence. The 1-year cumulative incidence rate of local recurrence was 27% (95% confidence interval 15, 39). On follow-up scans, three patterns of pleural abnormality were significantly associated with local recurrence: new/increased multiple pleural nodules (10 (48%) positive scans vs 0 control scans), new/increased diffuse nodular pleural thickening (7 (33%) positive scans vs 1 (1%) control scans), and new/increased focal pleural nodule (3 (14%) positive scans vs 1 (1%) control scan) (p < 0.001 for all).

CONCLUSIONS

Multiple new/increased pleural nodules are the feature most commonly present at local recurrence following IMPRINT; however, any pattern of increased nodular pleural thickening is suspicious.

KEY POINTS

• In patients with mesothelioma receiving intensity-modulated pleural radiation as part of multimodality therapy, increasing multiple pleural nodules is the computed tomography feature most commonly present at local recurrence. • In these patients, any CT pattern of increased nodular pleural thickening should be considered suspicious for local recurrence. • The most common sites of nonpleural recurrence were lung parenchyma, thoracic lymph nodes, and peritoneum.

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 Place and the Role of Radiation Therapy in the Treatment of Thymic Carcinoma

Thymic carcinomas arise from the epithelial cells of the thymus gland and are the most common tumors of the anterior mediastinum despite their overall rarity. Because of their rarity, their treatment remains a challenging topic. Although historically they have been treated surgically, radiation therapy (RT) has an important role either as a definitive or as a postoperative treatment. In this article, we present a review of the current therapies for the thymic carcinomas and try to identify the exact place of the RT in the optimal management of these patients.

Optimal gross tumor volume definition in lung-sparing intensity modulated radiotherapy for pleural mesothelioma: an in silico study

BACKGROUND

The gross tumor volume (GTV) definition for malignant pleural mesothelioma (MPM) is ill-defined. We therefore investigated which imaging modality is optimal: computed tomography (CT) with intravenous contrast (IVC), positron emission tomography-CT (PET/CT) or magnetic resonance imaging (MRI).

MATERIAL AND METHODS

Sixteen consecutive patients with untreated stage I-IV MPM were included. Patients with prior pleurodesis were excluded. CT with IVC, 18FDG-PET/CT and MRI (T2 and contrast-enhanced T1) were obtained. CT was rigidly co-registered with PET/CT and with MRI. Three sets of pleural GTVs were defined: GTV_CT, GTV_CT+PET/CT and GTV_CT+MRI. Quantitative and qualitative evaluations of the contoured GTVs were performed.

RESULTS

Compared to CT-based GTV definition, PET/CT identified additional tumor sites (defined as either separate nodules or greater extent of a known tumor) in 12/16 patients. Compared to either CT or PET/CT, MRI identified additional tumor sites in 15/16 patients (p = .7). The mean GTV_CT, GTV_CT+PET/CT and GTV_CT+MRI [±standard deviation (SD)] were 630.1 cm³ (±302.81), 640.23 cm³ (±302.83) and 660.8 cm³ (±290.8), respectively. Differences in mean volumes were not significant. The mean Jaccard Index was significantly lower in MRI-based contours versus all the others.

CONCLUSION

As MRI identified additional pleural disease sites in the majority of patients, it may play a role in optimal target volume definition.

Response evaluation in mesothelioma: Beyond RECIST

Malignant pleural mesothelioma (MPM) typically demonstrates a non-spherical growth pattern, so it is often difficult to accurately categorize change in tumour burden using size-based tumour response criteria (e.g., WHO (World Health Organisation), RECIST (Response Evaluation Criteria in Solid Tumours) and modified RECIST). Functional imaging techniques are applied to derive quantitative measurements of tumours, which reflect particular aspects of the tumour pathophysiology. By quantifying how these measurements change with treatment, it is possible to observe treatment effects. In this review, we survey the existing roles of CT and MRI for the management of MPM, including the currently applied size measurement criteria for the assessment of treatment response. New functional imaging techniques, such as positron emission tomography (PET), diffusion-weighted MRI (DWI) and dynamic contrast-enhanced MRI (DCE-MRI) that may potentially improve the assessment of treatment response will be highlighted and discussed.

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.

Optimizing hemithoracic pleural intensity-modulated radiation therapy for malignant pleural mesothelioma

The treatment of malignant pleural mesothelioma (MPM) remains challenging. Optimal management for resectable patients involves an aggressive approach, frequently using trimodality therapy. Historically, poor tumor control and profound pulmonary toxicity prevented conventional radiation therapy from being widely used. The advent of intensity-modulated radiation therapy was a major development in the delivery of radiation for MPM in the adjuvant setting, improving target coverage and dose homogeneity while maintaining acceptable toxicity profiles. Nevertheless, there remains a significant risk of severe pulmonary toxicity, ameliorated by careful target delineation, treatment planning and proactive toxicity management. Innovative technology, including arc therapy, simultaneous integrated boosts and proton therapy as well as neodjuvant delivery of radiation followed by pneumonectomy are being actively investigated to improve outcomes in the treatment of MPM.

Local and systemic therapies for malignant pleural mesothelioma

OPINION STATEMENT

Malignant pleural mesothelioma (MPM) is a challenging disease to treat with median overall survival times ranging between 9-17 months for all stages of disease. Recent clinical trials have improved our understanding of the biology of MPM. However, survival results are still not ideal. For early-stage MPM, patients should be evaluated for trimodality therapy in an experienced cancer center. If treating off-protocol, MPM patients should receive a surgical staging evaluation. The decision to proceed with surgical resection also should be considered after an extensive and thorough pulmonary and cardiac evaluation. If deemed a good surgical candidate, patients should receive surgical resection (pleurectomy/decortication or extrapleural pneumonectomy), adjuvant radiation therapy (hemithoracic external beam or intensity modulated radiation therapy), and either neoadjuvant or adjuvant chemotherapy (cisplatin-pemetrexed for 4 cycles). The optimal precise sequence of the trimodality is unclear and should be decided upon by a multidisciplinary consensus for each individual patient. In general, clinical trial participation should be encouraged. Several trials are currently underway to examine intraoperative therapies, vaccines, immunotherapy additions, and novel radiation therapy techniques. Advances in the field of MPM are reliant on participation in clinical trials and identifying biomarkers that are predictive for response to systemic therapies and prognostic for survival benefit.

Hemithoracic intensity modulated radiation therapy after pleurectomy/decortication for malignant pleural mesothelioma: toxicity, patterns of failure, and a matched survival analysis

PURPOSE

To investigate safety, efficacy, and recurrence after hemithoracic intensity modulated radiation therapy after pleurectomy/decortication (PD-IMRT) and after extrapleural pneumonectomy (EPP-IMRT).

METHODS AND MATERIALS

In 2009-2013, 24 patients with mesothelioma underwent PD-IMRT to the involved hemithorax to a dose of 45 Gy, with an optional integrated boost; 22 also received chemotherapy. Toxicity was scored with the Common Terminology Criteria for Adverse Events v4.0. Pulmonary function was compared at baseline, after surgery, and after IMRT. Kaplan-Meier analysis was used to calculate overall survival (OS), progression-free survival (PFS), time to locoregional failure, and time to distant metastasis. Failures were in-field, marginal, or out of field. Outcomes were compared with those of 24 patients, matched for age, nodal status, performance status, and chemotherapy, who had received EPP-IMRT.

RESULTS

Median follow-up time was 12.2 months. Grade 3 toxicity rates were 8% skin and 8% pulmonary. Pulmonary function declined from baseline to after surgery (by 21% for forced vital capacity, 16% for forced expiratory volume in 1 second, and 19% for lung diffusion of carbon monoxide [P for all = .01]) and declined still further after IMRT (by 31% for forced vital capacity [P=.02], 25% for forced expiratory volume in 1 second [P=.01], and 30% for lung diffusion of carbon monoxide [P=.01]). The OS and PFS rates were 76% and 67%, respectively, at 1 year and 56% and 34% at 2 years. Median OS (28.4 vs 14.2 months, P=.04) and median PFS (16.4 vs 8.2 months, P=.01) favored PD-IMRT versus EPP-IMRT. No differences were found in grade 4-5 toxicity (0 of 24 vs 3 of 24, P=.23), median time to locoregional failure (18.7 months vs not reached, P not calculable), or median time to distant metastasis (18.8 vs 11.8 months, P=.12).

CONCLUSIONS

Hemithoracic intensity modulated radiation therapy after pleurectomy/decortication produced little high-grade toxicity but led to progressive declines in pulmonary function; OS and PFS were better in PD-IMRT compared with EPP-IMRT.

Recent advances in radiotherapy for thoracic tumours

Radiation Oncology technology has continued to advance at a rapid rate and is bringing significant benefits to patients. This review outlines some of the advances in technology and radiotherapy treatment of thoracic cancers including brachytherapy, stereotactic radiotherapy, tomotherapy and intensity modulated radiotherapy. The importance of functional imaging with PET and management of movement are highlighted. Most of the discussion relates to non-small cell lung cancer but management of mesothelioma and small cell lung cancer are also covered. This technology has substantial benefits to patients in terms of decreasing toxicity both in the short and longer term.

Radiotherapy for thymic carcinoma: adjuvant, inductive, and definitive

Although historically thymoma and thymic carcinoma have been treated surgically, radiation therapy also has an important role, either as postoperative therapy to reduce the risk of mediastinal recurrence or as part of definitive treatment for patients who cannot undergo surgery. Induction chemotherapy and molecular targeted agents may also be appropriate for thymic carcinoma, the behavior of which resembles non-small-cell lung carcinoma more than that of thymoma or invasive thymoma and is increasingly being treated like lung cancer. We present here a review of current therapies for thymic malignancies and briefly discuss the potential benefits from novel technologies for such treatment.

¹⁸F-FDG-PET/CT in malignant mesothelioma

It is well known the useful role of ¹⁸F-FDG-PET/CT for differential diagnosis between benign and malignant disease, for staging, for monitoring response and for prognosis regarding mesothelioma. Recently, literature was enriched with new interesting studies regarding the potential applications of ¹⁸F-FDG-PET/CT in this field. The purpose of this review is to evaluate articles published on line (PubMed) from January 2011 until October 2012 in order to obtain an overview of recent progress of molecular imaging in malignant mesothelioma. The main topics concern the use of ¹⁸F-FDG-PET/CT in radiation therapy planning, monitoring of treatment (surgery/chemotherapy) response and prognosis assessment.

Prognostic ability of 18F-FDG PET/CT in the assessment of colorectal liver metastases

Modern multidisciplinary therapy for colorectal liver metastases (CRLM) is associated with significant morbidity and must be adapted to the patient's relative risk. The tools currently available to risk-stratify patients are limited. This study assessed the prognostic utility of metabolic measurements derived from(18)F-FDG PET compared with previously proposed prognostic scoring systems.

METHODS

Preoperative (18)F-FDG PET/CT studies from a series of 30 patients who underwent liver resection for CRLM after neoadjuvant chemotherapy were evaluated. Quantitative (18)F-FDG PET analysis calculated the maximum and mean standardized uptake value, metabolic tumor volume (MTV), and tumor glycolytic volume (TGV) as measures of the metabolic activity of tumors. The predictive value of these parameters was compared with that of 4 prognostic scores developed by Fong, Iwatsuki, Nordlinger, and Rees.

RESULTS

High MTV and TGV in patients before metastasectomy were significantly associated with poorer overall survival (MTV: P = 0.001; TGV: P = 0.004) and recurrence-free survival (MTV: P = 0.001, TGV; P = 0.002). Maximum and mean standardized uptake value did not show any significant predictive ability. Of the prognostic scores, prediction of outcome was most accurate using the Basingstoke index (area under the curve, 0.898).

CONCLUSION

Assessment of metabolic tumor burden with volumetric (18)F-FDG PET parameters appears to be a valuable adjunct in determining the biology of CRLM before surgical resection and may enable better risk stratification of patients.