Geometric dose prediction model for hemithoracic intensity-modulated radiation therapy in mesothelioma patients with two intact lungs

Our plain-English summary of Geometric dose prediction model for hemithoracic intensity-modulated radiation therapy in mesothelioma patients with two intact lungs, by L. Kuo, E.D. Yorke, V.A. Dumane, et al (Journal of Applied Clinical Medical Physics, 2016).

The study

• Authors: L. Kuo, E.D. Yorke, V.A. Dumane, A. Foster, Z. Zhang, J.G. Mechalakos, A.J. Wu, K.E. Rosenzweig, A. Rimner
• Journal: Journal of Applied Clinical Medical Physics
• Published: 2016;17(3):371-379
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The presence of two intact lungs makes it challenging to reach a tumoricidal dose with hemithoracic pleural intensity-modulated radiation therapy (IMRT) in patients with malignant pleural mesothelioma (MPM) who underwent pleurectomy/decortications or have unresectable disease. We developed an anatomy-based model to predict attainable prescription dose before starting optimization. Fifty-six clinically delivered IMRT plans were analyzed regarding correlation of prescription dose and individual and total lung volumes, planning target volume (PTV), ipsilateral normal lung volume and ratios: contralateral/ipsilateral lung (CIVR); contralateral lung/PTV (CPVR); ipsilateral lung /PTV (IPVR); ipsilateral normal lung /total lung (INTLVR); ipsilateral normal lung/PTV (INLPVR). Spearman's rank correlation and Fisher's exact test were used. Correlation between mean ipsilateral lung dose (MILD) and these volume ratios and between prescription dose and single lung mean doses were studied. The prediction models were validated in 23 subsequent MPM patients. CIVR showed the strongest correlation with dose (R=0.603,p<0.001) and accurately predicted prescription dose in the validation cases. INLPVR and MILD as well as MILD and prescription dose were significantly correlated (R=-0.784,p<0.001 and R=0.554,p<0.001, respectively) in the training and validation cases. Parameters obtainable directly from planning scan anatomy predict achievable prescription doses for hemithoracic IMRT treatment of MPM patients with two intact lungs. PACS number(s): 87.55.de, 87.55.dk.

In plain English

This study did not examine asbestos exposure. It concerned radiation treatment planning for people with malignant pleural mesothelioma who still had both lungs. The authors reviewed 56 plans for patients given radiation to the pleura on one side of the chest at their institution between 2005 and 2012. They tested whether volumes measured on the planning scan could predict the highest dose that could be prescribed within lung safety limits. The ratio of the opposite lung's volume to the treated-side lung's volume showed the strongest link with prescribed dose (R = 0.603, p less than 0.001). Among patients with a ratio at or above the median of 1.33, 79% received 48.6 or 50.4 Gy, compared with 25% of those below it. In 23 later patients, 8 of the 9 at or above the cutoff received at least 48.6 Gy, and 11 of the 14 below it received 46.8 Gy or less. The authors concluded that the ratio predicts whether at least 48.6 Gy is achievable. They said planners at other centers should check it before using it.

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 review of clinically delivered radiation treatment plans, used to build an anatomy-based dose prediction model, which was then tested in a later validation group
• Who was studied: Training set: all 56 malignant pleural mesothelioma patients with two intact lungs (unresectable disease or after pleurectomy/decortication) treated with hemithoracic pleural IMRT at the authors' institution (Memorial Sloan Kettering, New York) between 2005 and 2012. Validation set: 23 mesothelioma patients with two lungs treated after 2012.
• Exposure: Not asbestos. The study examined intensity-modulated radiation therapy to the pleura of one side of the chest, with a goal dose of 50.4 Gy in 28 fractions. It related the prescribed dose to lung and target volumes and their ratios.
• Main results:
  • Prescribed doses in the 56-patient training set: 50.4 Gy for 14 patients (25%), 48.6 Gy for 15 (27%), 46.8 Gy for 9 (16%), and 45.0 Gy or less for 18 (32%).
  • In the training set, the ratio of contralateral to ipsilateral lung volume (CIVR) had the strongest correlation with prescribed dose (R = 0.603, p less than 0.001).
  • Training set: among patients with CIVR of 1.33 or more, 79% received 48.6 Gy or 50.4 Gy (46% received 50.4 Gy). Among those with CIVR below 1.33, 25% received 48.6 to 50.4 Gy (4% received 50.4 Gy).
  • Training set: the median CIVR had sensitivity 0.759 and specificity 0.778 for predicting a prescription dose above 48.6 Gy.
  • Training set: mean ipsilateral lung dose was negatively correlated with IPVR (R = -0.658, p less than 0.001) and with INLPVR, the ratio of ipsilateral normal lung to target volume (R = -0.784, p less than 0.001).
  • Validation set (23 patients): of 9 with CIVR of 1.33 or more, 8 received 48.6 Gy or more. One received 46.8 Gy because of the heart constraint.
  • Validation set: of 14 with CIVR below 1.33, 11 received 46.8 Gy or less and 3 received 48.6 Gy or more.
  • In the validation set, the training-set median split of CIVR remained statistically significant (p less than 0.003, Fisher's exact test).
• The authors' conclusion: The authors concluded that, for these patients, a higher CIVR predicts the ability of an IMRT plan to reach a prescription dose of at least 48.6 Gy while keeping lung complication probability (LKB model) at or below 25%.
• Limitations the authors state:
  • The data came from one IMRT technique, one set of plan evaluation metrics, an experienced planning group, and two specific treatment planning systems.
  • Details of the correlation and the chosen cutoff could differ elsewhere, so other departments should evaluate the predictor before using it.
  • CIVR does not by itself determine the achievable dose. Other organs, planner skill, time and physician goals can also limit it.

Topics

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

Medical terms in this study, explained in our Lexicon: Intensity-Modulated Radiation Therapy (IMRT), Mesothelioma, Pleural Mesothelioma, Pleurectomy/Decortication (P/D), Unresectable.

Related studies

• Intensity-Modulated Radiation Therapy Improves the Target Coverage Over 3-D Planning While Meeting Lung Tolerance Doses for All Patients With Malignant Pleural Mesothelioma — S. Ulger, E. Cetin, et al. (2017)
• Intensity-modulated radiation therapy with simultaneous integrated boost in unresected left-sided pleural mesothelioma: a case report — S. Cilla, C. Digesú, et al. (2010)
• 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)
• Current readings: improvements in intensity-modulated radiation therapy for malignant pleural mesothelioma — K.E. Rosenzweig (2013)
• Early experience with intensity modulated proton therapy for lung-intact mesothelioma: A case series — H.Y. Pan, S. Jiang, et al. (2015)
• Dosimetric Correlates of Pulmonary Toxicity in Patients with Malignant Pleural Mesothelioma Receiving Radiation Therapy to the Intact Lungs — M.R. Thompson, V.A. Dumane, et al. (2019)

Browse return to medical research.