Restricted Field IMRT Dramatically Enhances IMRT Planning for Mesothelioma

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.

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.

Intensity-modulated radiotherapy is a safe and effective treatment for localized malignant pleural mesothelioma

Background

Malignant pleural mesothelioma (MPM) is a rare disease and management of localized disease is controversial. Radiotherapy has been shown to be useful after extrapleural pneumonectomy (EPP), as well as with less aggressive surgery. As no reports of the treatment of this disease have ever been published from Israel, we report our experience with MPM and intensity‐modulated radiotherapy (IMRT).

Methods

The complete medical records of patients treated for MPM at the Rabin Medical Center from 1 August 2007 to 31 March 2016 were reviewed. Twenty‐seven patients were treated with IMRT, either post‐EPP or without EPP. Patients received 54 Gy in 2 Gy fractions using the restricted field IMRT technique. Chemotherapy was administered sequentially in 26% of patients. Patients were followed up from the date of diagnosis to death or treatment failure.

Results

Seventy‐eight percent of patients had the epithelioid subtype. Nearly all patients were male (85%) and 90% of non‐surgical patients were administered chemotherapy compared to 56% of post‐EPP patients. All patients completed therapy and only 16% had grade 1–2 radiation pneumonitis, with no incidence of grade 3 or higher. The median follow‐up was 22 months and the mean overall survival was 34.9 months. The mean time to progression following radiation therapy was 26.7 months. The mean time to local and distant failure was 19 and 16 months, respectively.

Conclusions

IMRT for localized pleural mesothelioma is a tolerable and effective therapy both post‐EPP or without surgery. These results suggest that future investigation in this area is required.

Strategies for reducing ovarian dose in volumetric modulated arc therapy (VMAT) for postoperative uterine cervical cancer

OBJECTIVE

To reduce the ovarian dose with volumetric modulated arc therapy (VMAT), an original VMAT was designed with two types of arcs to restrict angles and fields (R-VMAT).

METHODS

The subjects were 11 patients who underwent ovarian transposition with clips left by a surgeon. Three methods, intensity-modulated radiotherapy (IMRT), standard VMAT (S-VMAT) and R-VMAT, were optimized for assessment of the ovarian dose with the target coverage kept high.

RESULTS

The homogeneity and conformity indexes for the planning target volume (PTV) were similar for the three methods. However, the average ± SD of the ovarian mean dose (OMD) was 5.0 ± 1.5, 4.9 ± 1.9 and 3.5 ± 1.4 Gy, and the percentage of ovarian volume exceeding 5 Gy (V5) was 41.5 ± 34.1%, 34.1 ± 38.05% and 8.4 ± 20.5% for IMRT, S-VMAT and R-VMAT, respectively. The OMD and V5 were significantly smaller for R-VMAT than for the other plans (p < 0.01). Correlation values between the OMD and the lateral distance from the ovaries to the PTV surface were 0.86, 0.81 and 0.82 for IMRT, S-VMAT and R-VMAT, respectively.

CONCLUSION

These findings suggest that R-VMAT delivered the lowest dose to the ovaries. To reduce the OMD to less than 3 Gy, ovaries should be transposed laterally 6.1 cm away from the PTV surface when R-VMAT is used. Advances in knowledge: When organs with high susceptibility to radiation, such as ovaries, are near the PTV, R-VMAT is superior to IMRT and S-VMAT.

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.

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.

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.

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.

Hemithoracic radiation therapy after extrapleural pneumonectomy for malignant pleural mesothelioma: Toxicity and outcomes at an Australian institution

INTRODUCTION

We aim to report the outcome of patients with malignant pleural mesothelioma who underwent extrapleural pneumonectomy (EPP) and adjuvant hemithoracic radiotherapy with or without chemotherapy at a single Australian institution.

METHOD

Between July 2004 and March 2013, 53 patients were referred for radiation treatment following EPP, of whom 49 were suitable for adjuvant treatment. Radiation treatment initially involved a 3D conformal, mixed electron/photon technique, delivering 45-50.4 Gy in 25-28 fractions (31 patients) and subsequently a nine-field intensity-modulated radiotherapy technique, delivering 50.4-54 Gy in 28-30 fractions (18 patients). Fifty-five per cent of patients also received pre-operative chemotherapy. We assessed toxicity, disease-specific and overall survival in patients who commenced radiation treatment.

RESULTS

Forty-one patients (84%) completed treatment as prescribed. Six patients stopped prematurely due to toxicity, and two with disease progression. Most patients discontinuing due to toxicity received over 90% of the prescribed dose. Common acute toxicities included nausea, fatigue, anorexia and dermatitis. Severe early toxicities were rare. Late toxicities were uncommon, with the exception of a persistent elevation in liver enzymes in those with right-sided disease. Neither clinical hepatitis nor radiation pneumonitis was documented. With a median follow up of 18.7 months, median disease-free and overall survival were 21.6 and 30.5 months, respectively, and 2-year overall survival was 57.3%.

CONCLUSION

Hemithoracic radiotherapy following EPP, although associated with significant early toxicity, is well tolerated. Most patients complete the prescribed treatment, and clinically significant late toxicities are rare.

Clinical experience of volumetric modulated arc therapy for malignant pleural mesothelioma after extrapleural pneumonectomy

The purpose of this study was to evaluate the efficacy and safety of volumetric modulated arc therapy (VMAT) after extrapleural pneumonectomy (EPP) in patients with malignant pleural mesothelioma (MPM). A total of 15 patients who received VMAT after EPP were enrolled. All patients were males, and the median age was 67 years (Stage IB in two, II in six, and III in seven patients). The clinical target volume (CTV) included the entire preoperative ipsilateral hemithorax and involved nodal stations. The CTV was generally expanded by 10-15 mm beyond the planning target volume (PTV). The dose prescription was designed to cover 95% of the PTV with 54 Gy in 30 fractions. The median follow-up period was 11 months. Treatment-related toxicities were evaluated by Common Terminology Criteria for Adverse Events (CTCAE) ver. 4. One-year local control, disease-free survival, and overall survival rates were 55.7% [95% confidence interval (CI): 25.6-85.8%], 29.3% (95% CI: 5.3-53.3%), and 43.1% (95% CI: 17.1-69.0%), respectively. According to the histological analysis, the one-year LC rate was significantly worse in patients with non-epithelial type (biphasic and sarcomatoid types) than in patients with epithelial type [epithelial type: 83.3% (95% CI, 53.5-100%), non-epithelial type: 0% (95% CI, 0%), P = 0.0011]. Grade 3 pneumonitis after VMAT was observed in three patients (20.0%); however, no patients died of pulmonary toxicity. VMAT appears to be relatively safe for patients with MPM after EPP because of the low pulmonary dose.

Clinical outcome of postoperative highly conformal versus 3D conformal radiotherapy in patients with malignant pleural mesothelioma

Background

Radiotherapy (RT) is currently under investigation as part of a trimodality treatment of malignant pleural mesothelioma (MPM). The introduction of highly conformal radiotherapy (HCRT) technique improved dose delivery and target coverage in comparison to 3-dimensional conformal radiotherapy (3DCRT). The following study was undertaken to investigate the clinical outcome of both radiation techniques.

Methods

Thirty-nine MPM patients were treated with neoadjuvant chemotherapy, extrapleural pneumonectomy (EPP) and adjuvant RT. Twenty-five patients were treated with 3DCRT, and 14 with HCRT (Intensity modulated radiotherapy or volumetric modulated arc therapy). Overall survival, disease free survival, locoregional recurrence and pattern of recurrence were assessed. A matched pair analysis was performed including 11 patients of each group.

Results

After matching for gender, age, histology, tumor stage and resection status, HCRT seemed superior to 3DCRT with a local relapse rate of 27.3% compared to 72.7% after 3DCRT (p = 0.06). The median time to local relapse was increased by 49% with HCRT in comparison to 3DCRT from 10.9 ± 5.4 months to 16.2 ± 3.1 months (p = 0.06). The median overall survival was 22.3 ± 15.3 months for HCRT and 21.2 ± 9.2 months for 3DCRT (p = 0.57). Recurrence analysis showed that in-field local relapses occurred in previously underdosed regions of the tumor bed in 16% of patients treated with 3DCRT and in 0% of HCRT patients.

Conclusions

The use of HCRT increases the probability of local control as compared to 3DCRT by improving target volume coverage. HCRT did not improve overall survival in this patient series due to the high rate of distant recurrences.

[Helical tomotherapy in the treatment of malignant pleural mesothelioma: The impact of low doses on pulmonary and oesophageal toxicity]

PURPOSE

To evaluate the adjuvant treatment of malignant pleural mesothelioma by helical tomotherapy and the impact of low doses on esophageal and pulmonary toxicity.

PATIENTS AND METHODS

Between June 2007 and May 2011, 29 patients diagnosed with malignant pleural mesothelioma received adjuvant radiotherapy by helical tomotherapy. The median age was 63 years (34-72). Histologically, 83 % of patients had epithelioid malignant pleural mesothelioma. Clinically, 45 % of patients were T3 and 55 % N0. Eighty six percent of the patients were treated by extrapleural pneumonectomy and 35 % received neoadjuvant chemotherapy with platinum and pemetrexed. The median dose in the pneumonectomy cavity was 50Gy at 2Gy/fraction.

RESULTS

The mean follow-up was 2.3 years after diagnosis. Overall survival at 1 and 2 years was 65 and 36 % respectively. The median survival from diagnosis was 18 months. Median lung volumes receiving 2, 5, 10, 13, 15 and 20Gy (V2, V5, V10, V13, V15 and V20) were 100, 98, 52, 36, 19 and 5 %. The median of the mean remaining lung dose was 11Gy. Two patients died of pulmonary complications, three patients had grade 3 lung toxicity, while esophageal grade 3-4 toxicity was observed in three other patients. No significant impact of clinical characteristics and dosimetric parameters were found on pulmonary toxicity, however a V10≥50 %, a V15≥15 % and mean lung dose of 10Gy or more had a tendency to be predictive of pulmonary toxicity (P<0.1). Moreover, in our analysis, the mean lung dose seems to have a significant impact on esophageal toxicity (P=0.03) as well as low doses to the controlateral lung: V5, V10 and V13 (P<0.05).

CONCLUSION

Helical tomotherapy is a promising technique in the multimodality treatment of malignant pleural mesothelioma. Low doses received by the contralateral lung appear to be the limiting factor. A dosimetric comparison with volumetric modulated arctherapy techniques would be interesting in this setting.

Intensity-modulated radiotherapy and volumetric-modulated arc therapy for malignant pleural mesothelioma after extrapleural pleuropneumonectomy

Radiotherapy reduces the local relapse rate after pleuropneumonectomy of malignant pleural mesothelioma (MPM). The optimal treatment technique with photons remains undefined. Comparative planning for intensity‐modulated radiotherapy (IMRT) and volumetric‐modulated arc therapy (VMAT) was performed. Six MPM patients with significant postoperative intrathoracic air cavities were planned with IMRT and VMAT. A dose comparison for the targets and organ at risks (OAR) was performed. Robustness was assessed in respect to the variation of target dose with change in volume of air cavities. VMAT reduced the dose to the contralateral lung by reducing the volume covered by 13 Gy and 20 Gy by a factor 1.8 and 2.8, in respect to IMRT (p=0.02). Dose distribution with VMAT was the most stable technique in regard to postsurgical air cavity variation. For IMRT, V90,V95, and the minimal target dose decreased by 40%, 64%, and 12% compared to 29%, 47%, and 7% with VMAT when air cavity decreased. Two arcs compared to one arc decreased the dose to all the organs at risk (OAR) while leaving PTV dose coverage unchanged. Increasing the number of arcs from two to three did not reduce the dose to the OAR further, but increased the beam‐on time by 50%. Using partial arcs decreased the beam‐on time by 43%. VMAT allows a lower lung dose and is less affected by the air cavity variation than IMRT. The best VMAT plans were obtained with two partial arcs. VMAT seems currently the most suitable technique for the treatment of MPM patients when air cavities are remaining and no adaptive radiotherapy is performed.

PACS number: 87.55.D‐

Practical methods for improving dose distributions in Monte Carlo-based IMRT planning of lung wall-seated tumors treated with SBRT

Current commercially available planning systems with Monte Carlo (MC)‐based final dose calculation in IMRT planning employ pencil‐beam (PB) algorithms in the optimization process. Consequently, dose coverage for SBRT lung plans can feature cold‐spots at the interface between lung and tumor tissue. For lung wall (LW)‐seated tumors, there can also be hot spots within nearby normal organs (example: ribs). This study evaluated two different practical approaches to limiting cold spots within the target and reducing high doses to surrounding normal organs in MC‐based IMRT planning of LW‐seated tumors. First, “iterative reoptimization”, where the MC calculation (with PB‐based optimization) is initially performed. The resultant cold spot is then contoured and used as a simultaneous boost volume. The MC‐based dose is then recomputed. The second technique uses noncoplanar beam angles with limited path through lung tissue. Both techniques were evaluated against a conventional coplanar beam approach with a single MC calculation. In all techniques the prescription dose was normalized to cover 95% of the PTV. Fifteen SBRT lung cases with LW‐seated tumors were planned. The results from iterative reoptimization showed that conformity index (CI) and/or PTV dose uniformity (UPTV) improved in 12/15 plans. Average improvement was 13%, and 24%, respectively. Nonimproved plans had PTVs near the skin, trachea, and/or very small lung involvement. The maximum dose to 1cc volume (D1cc) of surrounding OARs decreased in 14/15 plans (average 10%). Using noncoplanar beams showed an average improvement of 7% in 10/15 cases and 11% in 5/15 cases for CI and UPTV, respectively. The D1cc was reduced by an average of 6% in 10/15 cases to surrounding OARs. Choice of treatment planning technique did not statistically significantly change lung V5. The results showed that the proposed practical approaches enhance dose conformity in MC‐based IMRT planning of lung tumors treated with SBRT, improving target dose coverage and potentially reducing toxicities to surrounding normal organs.

PACS numbers: 87.55.de, 87.55.kh

Adjuvant intensity-modulated proton therapy in malignant pleural mesothelioma. A comparison with intensity-modulated radiotherapy and a spot size variation assessment

PURPOSE

Intensity-modulated radiation therapy (IMRT) is the state-of-the-art treatment for patients with malignant pleural mesothelioma (MPM). The goal of this work was to assess whether intensity-modulated proton therapy (IMPT) could further improve the dosimetric results allowed by IMRT.

PATIENTS AND METHODS

We re-planned 7 MPM cases using both photons and protons, by carrying out IMRT and IMPT plans. For both techniques, conventional dose comparisons and normal tissue complication probability (NTCP) analysis were performed. In 3 cases, additional IMPT plans were generated with different beam dimensions.

RESULTS

IMPT allowed a slight improvement in target coverage and clear advantages in dose conformity (p < 0.001) and dose homogeneity (p = 0.01). Better organ at risk (OAR) sparing was obtained with IMPT, in particular for the liver (D(mean) reduction of 9.5 Gy, p = 0.001) and ipsilateral kidney (V(20) reduction of 58%, p = 0.001), together with a very large reduction of mean dose for the contralateral lung (0.2 Gy vs 6.1 Gy, p = 0.0001). NTCP values for the liver showed a systematic superiority of IMPT with respect to IMRT for both the esophagus (average NTCP 14% vs. 30.5%) and the ipsilateral kidney (p = 0.001). Concerning plans obtained with different spot dimensions, a slight loss of target coverage was observed along with sigma increase, while maintaining OAR irradiation always under planning constraints.

CONCLUSION

Results suggest that IMPT allows better OAR sparing with respect to IMRT, mainly for the liver, ipsilateral kidney, and contralateral lung. The use of a spot dimension larger than 3 × 3 mm (up to 9 × 9 mm) does not compromise dosimetric results and allows a shorter delivery time.

ZDHHC8 knockdown enhances radiosensitivity and suppresses tumor growth in a mesothelioma mouse model

Mesothelioma is an aggressive tumor caused by asbestos exposure, the incidence of which is predicted to increase globally. The prognosis of patients with mesothelioma undergoing conventional therapy is poor. Radiation therapy for mesothelioma is of limited use because of the intrinsic radioresistance of tumor cells compared with surrounding normal tissue. Thus, a novel molecular-targeted radiosensitizing agent that enhances the radiosensitivity of mesothelioma cells is required to improve the therapeutic efficacy of radiation therapy. ZDHHC8 knockdown reduces cell survival and induces an impaired G(2) /M checkpoint after X-irradiation in HEK293 cells. In the present study, we further analyzed the effect of the combination of ZDHHC8 knockdown and X-irradiation and assessed its therapeutic efficacy in mesothelioma models. SiRNA-induced ZDHHC8 knockdown in 211H and H2052 mesothelioma cells significantly reduced cell survival after X-irradiation. In 211H cells treated with ZDHHC8 siRNA and X-irradiation, the G(2) /M checkpoint was impaired and there was an increase in the number of cells with micronuclei, as well as apoptotic cells, in vitro. In 211H tumor-bearing mice, ZDHHC8 siRNA and X-irradiation significantly suppressed tumor growth, whereas ZDHHC8 siRNA alone did not. Immunohistochemical analysis showed decreased cell proliferation and induction of apoptosis in tumors treated with ZDHHC8 siRNA and X-irradiation, but not with ZDHHC8 siRNA alone. These results suggest that ZDHHC8 knockdown with X-irradiation induces chromosomal instability and apoptosis through the impaired G(2) /M checkpoint. In conclusion, the combination of ZDHHC8 siRNA and X-irradiation has the potential to improve the therapeutic efficacy of radiation therapy for malignant mesothelioma.

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.

Helical tomotherapy for resected malignant pleural mesothelioma: dosimetric evaluation and toxicity

This study evaluated adjuvant helical tomotherapy after extrapleural pneumonectomy ± neo-adjuvant chemotherapy in 24 patients with malignant pleural mesothelioma. Toxicity was judged acceptable despite 2 cases (8%) of suspected grade 5 pneumonitis. With a mean follow-up of 7 months, 5 patients had distant and 2 local and distant failure.

Mesothelioma at era of helical tomotherapy: results of two institutions in combining chemotherapy, surgery and radiotherapy

PURPOSE

There is a scarce clinical experience about adjuvant helical tomotherapy (HT) in patients affected by malignant pleural mesothelioma (MPM) even though it appears as a useful technique to treat complex volume as the pleural cavity, and seems to have better dose distribution than the "classic" intensity modulated radiotherapy (IMRT).

METHODS AND MATERIALS

Twenty-four patients received adjuvant radiotherapy (RT) by HT from August 1st, 2007 to December 1st, 2009 at Curie Institute (Paris) and René Gauducheau Cancer Center (Nantes). Thirteen patients had neoadjuvant chemotherapy. Extrapleural pleuropneumonectomy (EPP) was done in 23 patients. Median dose to PTV was 50Gy [48.7-55.9Gy] (2Gy/fraction). Acute and long term toxicities, disease free survival (DFS), overall survival (OS) and relapses are presented.

RESULTS

Average follow up after RT was 7 months. The disease was staged mostly as T2-T3, N1-N2. Nineteen patients had epithelial type histology. Most patients tolerated radiotherapy with grade 1-2 side effects: redness of the skin, light cough or dyspnea, fatigue, nausea and odynophagia, mild increase of the post-operative thoracic pain. Grade 3 pneumonitis was suspected in 2 patients. Two grade 5 pneumonitis were also suspected. Eleven patients had a follow up of more than 6 months and no long term side effects related with HT were noted. At 24 months, 51.8% of patients were free of disease. Thirty percent of patients relapsed, with 2 patients presenting local relapses. Two patients died from recurrence.

CONCLUSION

With limited follow up, HT has comparable toxicity to those observed with traditional IMRT. Higher radiation dose and good coverage results in excellent local control.

[Value of tomotherapy in malignant pleural mesothelioma: first clinical results]

INTRODUCTION

There is little clinical data about the place of helicoidal tomotherapy (HT) in the treatment of malignant pleural mesothelioma (MPM). This new form of intensity modulated radiotherapy (IMRT) has great theoretical advantages in large and complex volumes when compared to "traditional" forms of radiotherapy.

PATIENTS AND METHODS

Fourteen patients diagnosed with MPM received adjuvant radiotherapy by HT. The patients were treated at the Curie Institute and the René Gauducheau Centre, starting in August 12007. All patients had a complete initial staging, an extrapleural pneumonectomy (EPP), and a minimum follow-up of six months. The median dose prescribed to the surgical cavity was 50 Gy (48-54 Gy) in 2 Gy (1.80-2.07) fractions. High dose regions received concomitant 57 Gy (54-69 Gy) in 2.16 Gy (2.00-2.30 Gy) fractions.

RESULTS

Median follow-up was 12.6 months after ending HT. Seven patients received neoadjuvant chemotherapy (cisplatin or carboplatin, and pemetrexed). Eight patients were staged pT3 and five were staged pN1-2. HT was well tolerated. Two patients had suspected G5 radiation pneumonitis within 6 months of ending HT. Of the 12 patients who survived treatment, six relapsed (in average 5.1 months after HT): distant. Four relapses were distant; two relapses were both local and distant. Three patients died after their initial relapse. After initial diagnosis, the median survival was 18.4 months. A learning curve was observed in the optimization of the dosimetric parameters.

CONCLUSION

Helicoidal tomotherapy is a reliable, quite well tolerated, and efficient way of treating MPM patients after an EPP.

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.

Analysis of the effect of radiotherapy on malignant pleural mesothelioma when given on adjuvant or palliative basis

Background and objective

This retrospective study was designed to evaluate the response and survival of malignant pleural mesothelioma to radiotherapy when delivered with surgery and chemotherapy and when delivered alone or with chemotherapy.

Methods

A study for 110 patients with malignant pleural mesothelioma who presented to radiotherapy department, National Cancer Institute, Cairo and received radiation therapy in the period from January 1999 to July 2007.

Results

Forty-six patients (41.8%) received trimodality therapy (surgery & adjuvant or neoadjuvant chemotherapy & adjuvant radiotherapy), while bimodality therapy (chemotherapy & radiotherapy) in 38 patients (34.5%), while 26 patients (23.6%) received single modality therapy (palliative radiotherapy), 22 patients (20%) developed local recurrence, 22 patients (20%) developed distant metastases months, 14 patients (12.7%) developed local disease progression, 25 patients (22.7%) are still alive and free of disease at time of reporting. The median survival for all patients was 16 months, while 12 and 18 months overall survival were 63.6% & 31.8% respectively while median survival for stage Ⅱ, Ⅲ, Ⅳ patients was 16.5, 12.5 and 8 months respectively.

Conclusion

Multimodality approach involving surgery, chemotherapy and radiotherapy have been evaluated and proved its superiority in improving survival, especially in stages Ⅱ.

Proton therapy for malignant pleural mesothelioma after extrapleural pleuropneumonectomy

PURPOSE

To perform comparative planning for intensity-modulated radiotherapy (IMRT) and proton therapy (PT) for malignant pleural mesothelioma after radical surgery.

METHODS AND MATERIALS

Eight patients treated with IMRT after extrapleural pleuropneumonectomy (EPP) were replanned for PT, comparing dose homogeneity, target volume coverage, and mean and maximal dose to organs at risk. Feasibility of PT was evaluated regarding the dose distribution with respect to air cavities after EPP.

RESULTS

Dose coverage and dose homogeneity of the planning target volume (PTV) were significantly better for PT than for IMRT regarding the volume covered by >95% (V95) for the high-dose PTV. The mean dose to the contralateral kidney, ipsilateral kidney, contralateral lung, liver, and heart and spinal cord dose were significantly reduced with PT compared with IMRT. After EPP, air cavities were common (range, 0-850 cm(3)), decreasing from 0 to 18.5 cm(3)/day. In 2 patients, air cavity changes during RT decreased the generalized equivalent uniform dose (gEUD) in the case of using an a value of < - 10 to the PTV2 to <2 Gy in the presence of changing cavities for PT, and to 40 Gy for IMRT. Small changes were observed for gEUD of PTV1 because PTV1 was reached by the beams before air.

CONCLUSION

Both PT and IMRT achieved good target coverage and dose homogeneity. Proton therapy accomplished additional dose sparing of most organs at risk compared with IMRT. Proton therapy dose distributions were more susceptible to changing air cavities, emphasizing the need for adaptive RT and replanning.

Volumetric modulation arc radiotherapy compared with static gantry intensity-modulated radiotherapy for malignant pleural mesothelioma tumor: a feasibility study

PURPOSE

A planning study was performed to evaluate RapidArc (RA), a volumetric modulated arc technique, on malignant pleural mesothelioma. The benchmark was conventional fixed-field intensity-modulated radiotherapy (IMRT).

METHODS AND MATERIALS

The computed tomography data sets of 6 patients were included. The plans for IMRT with nine fixed beams were compared against double-modulated arcs with a single isocenter. All plans were optimized for 15-MV photon beams. The dose prescription was 54 Gy to the planning target volume. The planning objectives for the planning target volume were a minimal dose of >95% and maximal dose of <107%. For the organs at risk, the parameters were as follows: contralateral lung, percentage of volume receiving 5 Gy (V(5 Gy)) <60%, V(20 Gy) < 10%, mean <10.0 Gy; liver, V(30 Gy) <33%, mean <31 Gy; heart, V(45 Gy) <30%, V(50 Gy) <20%, dose received by 1% of the volume (D(1%)) <60 Gy; contralateral kidney, V(15 Gy) <20%; spine, D(1%) <45 Gy; esophagus, V(55 Gy) <30%; and spleen, V(40 Gy) <50%. The monitor units (MUs) and delivery time were scored to measure the treatment efficiency. The pretreatment portal dosimetry scored delivery to the calculation agreement with the Gamma Agreement Index.

RESULTS

RA and IMRT provided equivalent coverage and homogeneity. Both techniques fulfilled objectives on organs at risk with a tendency of RA to improve sparing. The conformity index was 1.9 +/- 0.1 for RA and IMRT. The number of MU/2 Gy was 734 +/- 82 for RA and 2,195 +/- 317 for IMRT. The planning vs. delivery agreement revealed a Gamma Agreement Index for IMRT of 96.0% +/- 2.6% and for RA of 95.7% +/- 1.5%. The treatment time was 3.7 +/- 0.3 min for RA and 13.4 +/- 0.1 min for IMRT.

CONCLUSION

RA demonstrated compared with conventional IMRT, similar target coverage and better dose sparing to the organs at risks. The number of MUs and the time required to deliver a 2-Gy fraction were much lower for RA, allowing the possibility to incorporate this technique in the treatment options for mesothelioma patients.

Radiation therapy options for malignant pleural mesothelioma

The role of radiation therapy (RT) in the curative treatment of malignant pleural mesothelioma remains undefined. No data clearly support treatment of unresected mesothelioma with definitive RT. Early reports showed that RT was associated with unacceptable toxicity, but recent limited data suggest that treatment with intensity-modulated radiation therapy (IMRT) may be tolerable. Adjuvant RT after pleurectomy is also challenging, and similarly, no clear efficacy has been demonstrated. Some approaches, such as IMRT to the circumferential pleural envelope, appear feasible, but the fact that this approach does not address the disease in the fissures is problematic. The best setting in which to deliver RT is after extrapleural pneumonectomy, but the large and irregular target volume and multiple and adjacent sensitive normal structures make this complex. The Memorial Sloan-Kettering Cancer Center matched photon/electron technique is associated with acceptable efficacy and toxicity, but is limited in that it does not achieve complete coverage of the target volume to the prescription dose. The best dosimetry is achieved using IMRT, and this approach is the most promising to date. However, the toxicity profile can be severe, and the relevant predictive factors for complications are not fully understood. For these reasons, physicians should exercise caution, and IMRT after extrapleural pneumonectomy is probably best offered only by experienced teams or on protocol until further data have been gathered. New techniques such as helical tomotherapy and/or IMRT with the addition of electrons may also have a role in future treatment. RT can palliate symptoms provided the disease is confined to a tolerable radiation field.

Improving the outcome in malignant pleural mesothelioma: nonaggressive or aggressive approach?

PURPOSE OF REVIEW

The treatment of malignant pleural mesothelioma continues to be a clinical challenge. The question, however, is no longer whether to provide active treatment or not, but how aggressive the treatment should be in view of the limited life expectancy of patients with this disease.

RECENT FINDINGS

With platin and pemetrexed-based combination chemotherapy having become the preferred systemic therapy, the major questions now evolve around the identification of a suitable second line therapy and the quest for innovative new approaches. Surgical interventions from pleurectomy and decortication to extrapleural pneumonectomy have increasingly come of use in specialized centres. With neoadjuvant chemotherapy and extrapleural pneumonectomy median survival times of almost 2 years have been reported. Studies on high-dose hemithoracic radiotherapy after extrapleural pneumonectomy suggested a beneficial effect on local recurrence. However, both extrapleural pneumonectomy and high-dose hemithoracic radiotherapy are associated with potential treatment-related mortality and morbidity and cannot yet be recommended outside specialized centres.

SUMMARY

More than ever, the diagnosis and treatment of patients with malignant pleural mesothelioma mandate a multidisciplinary approach.

Malignant pleural mesothelioma

Malignant pleural mesothelioma continues to be a challenge. The diagnosis and treatment of patients with malignant pleural mesothelioma requires a multidisciplinary approach. The diagnosis is best made by thoracoscopic biopsy and the aid of immunohistochemistry. Molecular studies identified inactivation of the neurofibromatosis-2 gene and INK4alpha/ARF to be key events in tumorigenesis. Based on the results of a Phase III trial, the combination of cisplatin with pemetrexed has become the preferred choice for chemotherapy, although there is suggestive evidence for the activity of other platin combinations based on Phase II studies. The optimal second-line chemotherapy remains to be defined. Surgical interventions ranging from pleurectomy/decortication to extrapleural pneumonectomy are increasingly offered in specialized centers, and the results of multimodality approaches with neoadjuvant or adjuvant chemotherapy and extrapleural pneumonectomy are encouraging. Ongoing investigations are defining the role of postoperative radiotherapy and the clinical activity of tyrosine kinase inhibitors targeting VEGFR2, histone deacetylase inhibitors and proteosome inhibitors.

Evaluation of the dose calculation accuracy in intensity-modulated radiation therapy for mesothelioma, focusing on low doses to the contralateral lung

This study compares Monte Carlo (MC) with conventional treatment planning system (TPS) calculations. The EGS4nrc MC code, BEAMnrc, was commissioned to simulate a Varian 21Ex Linac. The accuracy of the simulations, including points blocked by the jaws, was evaluated by comparing MC with ion chamber and MOSFET measurements. Eight mesothelioma IMRT cases were planned using Eclipse (pencil beam and superposition convolution algorithms). Dose distributions were recalculated using BEAMnrc/DOSxyz, and compared with TPS. MC agreed with experimental results for IMRT fields within 3% (96% of points). For regions blocked by the jaws, average agreement between MC and experiment was better than 5% up to 20 cm from isocenter. The pencil beam algorithm underestimated lung MLD, V20, and V5, compared with MC, by a mean (range) of 16% (11-22%), 9.0% (2.4-30.1%), and 11.8% (2-30%), respectively. The superposition convolution algorithm gave better agreement of 8.5% (0-17%), 4% (0-12%) and 0% (-6-6%). Mean dose to the targets was better than +/- 5% in all cases. In conclusion, there is excellent correlation between TPS and MC calculations for the target doses. The pencil beam algorithm and superposition convolution algorithms both underestimate lung dose parameters, but the superposition convolution dose offers improvements in dose calculation accuracy for these patients.

Pulmonary toxicity following IMRT after extrapleural pneumonectomy for malignant pleural mesothelioma

BACKGROUND AND PURPOSE

The combination of chemotherapy, surgery, and radiotherapy has improved the prognosis for patients with malignant pleural mesothelioma (MPM). Intensity-modulated radiotherapy (IMRT) has allowed for an increase in dose to the pleural cavity and a reduction in radiation doses to organs at risk. The present study reports and analyses the incidence of fatal pulmonary toxicity in patients treated at Rigshospitalet, Copenhagen.

MATERIALS AND METHODS

Twenty-six patients were treated with induction chemotherapy followed by extrapleural pneumonectomy and IMRT between April 2003 and April 2006. The entire preoperative pleural surface area was treated to 50 Gy and areas with residual disease or close surgical margins were treated to 60 Gy in 30 fractions.

RESULTS

The main toxicities were nausea, vomiting, esophagitis, dyspnea, and thrombocytopenia. One patient died from an intracranial hemorrhage during severe thrombocytopenia. Four patients (15%) experienced grade 5 lung toxicity, i.e. pneumonitis 19-40 days after the completion of radiotherapy. Patients with pneumonitis had a significantly larger lung volume fraction receiving 10 Gy or more (V10) (median: 60.3%, range 56.4-83.2%) compared to patients without pneumonitis (median: 52.6%, range: 25.6-80.3%) (p=0.02). Mean lung dose (MLD) was also significantly higher in patients who developed pneumonitis (median 13.9 Gy, range: 13.6-14.2 Gy) than in patients who did not (median=12.4 Gy, range: 8.4-15.4 Gy) (p=0.04).

CONCLUSIONS

Significant differences in MLD and V10 for patients with fatal pulmonary toxicity compared to patients without fatal lung toxicity have been demonstrated. Based on the presented data local lung dose constraints have been modified in order to avoid unacceptable toxicity.

Radiotherapy for malignant pleural mesothelioma

BACKGROUND

Malignant pleural mesothelioma is a relatively uncommon disease, but the incidence is increasing and is expected to peak in many developed countries in the next two decades. The management of patients with malignant mesothelioma is controversial. Very few patients are suitable for any potentially curative treatment and the effectiveness of radical therapy with surgery, radiotherapy and/or chemotherapy in curing patients or prolonging survival is uncertain. The role of radiotherapy is controversial although it has been used as part of multimodal therapy. The present review will try to clarify these uncertainties.

OBJECTIVES

To assess the effectiveness and safety of radiotherapy on patients with malignant pleural mesothelioma in any stage of the disease.

SEARCH STRATEGY

Both electronic and handsearches were conducted. All randomised controlled clinical trials were searched in electronic databases such as: Cochrane Central Register of Controlled Trials, MEDLINE and EMBASE. Handsearching was aimed at the identification of evidence by reviewing journals not indexed in databases, proceedings of conferences and/or scientific meetings.

SELECTION CRITERIA

All randomised controlled clinical trials using radiotherapy for malignant pleural mesothelioma in any stage, alone or combined with other therapies in patients of either sex and any age, were included. Studies without a control group were excluded.

DATA COLLECTION AND ANALYSIS

There were no studies that fulfilled the inclusion criteria.

MAIN RESULTS

To date we have not found any reports of randomised comparisons of radiotherapy alone or combined for patients with malignant pleural mesothelioma.

AUTHORS' CONCLUSIONS

As radiotherapy has never been compared to chemotherapy or surgery or to best supportive care (as part of combination therapy) in a prospective, randomised trial, no data exist supporting one or the other treatment as a better option for patients with malignant pleural mesothelioma. There is a need for multicentre controlled randomised trials assessing the role of radiotherapy in the radical treatment of malignant pleural mesothelioma. The studies should be limited to patients with malignant pleural mesothelioma, classified by stage, cytology and type of radiotherapy. The type of radiotherapy should be defined in advance and variables of radiotherapy dose definition and delivery should be carefully controlled.