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

Our plain-English summary of Intensity-Modulated Radiation Therapy Improves the Target Coverage Over 3-D Planning While Meeting Lung Tolerance Doses for All Patients With Malignant Pleural Mesothelioma, by S. Ulger, E. Cetin, S. Catli, et al (Technology in Cancer Research & Treatment, 2017).

The study

• Authors: S. Ulger, E. Cetin, S. Catli, H. Sarac, D. Kilic, H. Bora
• Journal: Technology in Cancer Research & Treatment
• Published: 2017;16(3):332-338
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

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.

In plain English

This was a retrospective radiation-planning (dosimetric) study from Gazi University in Ankara, Turkey. It did not study asbestos exposure. The authors reviewed radiation planning records of 12 patients with malignant pleural mesothelioma who had trimodality treatment. For each patient they compared two computer plans for radiation to the whole affected side of the chest (50.4 Gy in 1.8 Gy daily fractions): 3-D conformal and intensity-modulated radiation therapy (IMRT). On average, 100% of the target area received at least 95% of the prescribed dose with IMRT, compared with 71.29% with the 3-D technique. The 3-D plans gave statistically lower doses to the remaining lung. The authors reported that the IMRT plans still met their lung limits (mean lung dose below 10 Gy, V5 below 60%, V20 below 10%), though Table 2 lists a highest IMRT V5 of 60%. Several figures differ between the article's text, abstract and tables. The authors concluded that IMRT can deliver an effective tumor dose while keeping lung dose below tolerance for pneumonitis. They noted that, as a planning study, it allows no conclusions about tumor control or side effects, and that the number of patients was small.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective dosimetric comparison of radiation treatment plans (24 plans: one 3-D conformal and one IMRT plan for each of 12 patients); no patient outcomes were measured
• Who was studied: Radiation planning records of 12 patients with malignant pleural mesothelioma who underwent trimodality treatment (surgery, chemotherapy and radiation), Department of Radiation Oncology, Gazi University, Ankara, Turkey. There were 7 men and 5 women. The tumor was right-sided in 8 patients. The study years are not given.
• Exposure: Not asbestos. The study compared two radiation therapy planning techniques, 3-D conformal radiation therapy (photon and electron fields) and intensity-modulated radiation therapy (7 to 9 beam angles). Both were planned to the entire hemithorax at 50.4 Gy in 1.8 Gy daily fractions.
• Main results:
  • Target coverage: the share of the planning target volume receiving at least 95% of the prescribed dose (PTV95) averaged 100% in IMRT plans and 71.29% in 3-D conformal plans
  • Dose homogeneity (PTV105): the text reports a mean of 12.25% for IMRT and 35.81% for 3-D conformal plans. Table 1 gives 11.14% for IMRT and 35.69% for 3-D conformal, with p less than .0001.
  • The 3-D conformal plans gave statistically lower mean lung dose and lung V5 than the IMRT plans
  • Mean dose to the contralateral lung: 7.36 (range 5.6 to 8.4) in IMRT plans and 1.13 (range 0.62 to 1.77) in 3-D conformal plans. The values are printed with a percent sign. Table 2 gives 7.47 (5.6 to 9.2) for IMRT.
  • Lung V5 (percentage of lung receiving 5 Gy or more): mean 57.74% (range 47.0% to 59.9%) in IMRT plans and 2.42% (range 0.0% to 4.9%) in 3-D conformal plans. Table 2 gives 57.89% (range 47 to 60) for IMRT.
  • Lung V20 (percentage of lung receiving 20 Gy or more): mean 4.5% (range 0.5% to 9.5%) in IMRT plans and 0.68% (range 0.0% to 6.22%) in 3-D conformal plans (P = .04)
  • The authors report that their IMRT lung limits (mean lung dose below 10 Gy, V5 below 60%, V20 below 10%) were met in the IMRT plans through beam angle correction and optimization. Table 2, however, lists a highest IMRT lung V5 of 60%.
  • Mean heart dose did not differ statistically between IMRT and 3-D conformal plans (Table 2: 18.7 vs 13.33, p .062)
  • Spinal cord maximum dose and the percentage of ipsilateral kidney receiving 15 Gy did not differ between the two techniques
  • Table 2 shows a higher mean esophagus dose in IMRT plans (40.02, range 30.1 to 44.4) than in 3-D conformal plans (31.67, range 24.1 to 36.81), p less than .0001
• The authors' conclusion: The authors concluded that, for the large and complex target volume of malignant pleural mesothelioma, IMRT can deliver an effective tumor-killing radiation dose while keeping lung dose below the tolerance for pneumonitis
• Limitations the authors state:
  • Retrospective design
  • It is only a dosimetric (planning) study, so no conclusions can be drawn about tumor control or toxicity in patients
  • Small number of patients

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Intensity-Modulated Radiation Therapy (IMRT), Pleural Mesothelioma.

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• Intensity-modulated radiation therapy with simultaneous integrated boost in unresected left-sided pleural mesothelioma: a case report — S. Cilla, C. Digesú, et al. (2010)
• Current readings: improvements in intensity-modulated radiation therapy for malignant pleural mesothelioma — K.E. Rosenzweig (2013)
• Adjuvant intensity-modulated proton therapy in malignant pleural mesothelioma. A comparison with intensity-modulated radiotherapy and a spot size variation assessment — S. Lorentini, M. Amichetti, et al. (2012)
• Disease-Related Outcomes and Toxicities of Intensity Modulated Radiation Therapy After Lung-Sparing Pleurectomy for Malignant Pleural Mesothelioma: A Systematic Review — R. Patel, E.B. Ludmir, et al. (2020)
• Patterns of failure, toxicity, and survival after extrapleural pneumonectomy and hemithoracic intensity-modulated radiation therapy for malignant pleural mesothelioma — D.R. Gomez, D.S. Hong, et al. (2013)

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