Intensity-Modulated Radiotherapy Might Increase Pneumonitis Risk Relative to Three-Dimensional Conformal Radiotherapy in Patients Receiving Combined Chemotherapy and Radiotherapy: A Modeling Study of Dose Dumping

• Published in: International journal of radiation oncology, biology, physics Vol. 80; no. 3; pp. 893 - 899
• Main Authors: Vogelius, Ivan S., Ph.D, Westerly, David C., Ph.D, Cannon, George M., M.D, Mackie, Thomas R., Ph.D, Mehta, Minesh P., M.D, Sugie, Chikao, M.D, Bentzen, Søren M., Ph.D., D.Sc
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.07.2011; Elsevier
• Subjects: Antineoplastic agents; Biological and medical sciences; BODY; Carcinoma, Non-Small-Cell Lung - drug therapy; Carcinoma, Non-Small-Cell Lung - radiotherapy; CHEMOTHERAPY; Combined Modality Therapy - adverse effects; Combined Modality Therapy - methods; COMBINED THERAPY; Combined treatments (chemotherapy of immunotherapy associated with an other treatment); COMPUTERIZED TOMOGRAPHY; CT-GUIDED RADIOTHERAPY; DIAGNOSTIC TECHNIQUES; DISEASES; DOSES; Functional damage model; HAZARDS; Hematology, Oncology and Palliative Medicine; Humans; Lung Neoplasms - drug therapy; Lung Neoplasms - radiotherapy; LUNGS; Lyman model; Medical sciences; MEDICINE; Models, Biological; NEOPLASMS; NUCLEAR MEDICINE; ORGANS; Pharmacology. Drug treatments; PNEUMONITIS; Pneumonitis risk; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; Radiation Pneumonitis - chemically induced; Radiation Pneumonitis - etiology; RADIOLOGY; RADIOLOGY AND NUCLEAR MEDICINE; RADIOTHERAPY; Radiotherapy Dosage; Radiotherapy, Conformal - adverse effects; Radiotherapy, Intensity-Modulated - adverse effects; RESPIRATORY SYSTEM; SIMULATION; THERAPY; THRESHOLD DOSE; TOMOGRAPHY; Chemotherapy; Functional damage model; Lyman model; Pneumonitis risk; Radiotherapy; Antineoplastic agent; Human; Biological properties; Lung disease; Pneumonia; Respiratory disease; Toxicity; Modeling; Conformal radiotherapy; Radiation dose; Intensity modulated radiotherapy; Treatment; Risk factor; Radiation injury; Complication; Models; Combined treatment; Dosimetry; Treatment planning
• ISSN: 0360-3016; 1879-355X
• DOI: 10.1016/j.ijrobp.2010.12.073

Purpose To model the possible interaction between cytotoxic chemotherapy and the radiation dose distribution with respect to the risk of radiation pneumonitis. Methods and Materials A total of 18 non–small-cell lung cancer patients previously treated with helical tomotherapy at the University of Wisconsin were selected for the present modeling study. Three treatment plans were considered: the delivered tomotherapy plans; a three-dimensional conformal radiotherapy (3D-CRT) plan; and a fixed-field intensity-modulated radiotherapy (IMRT) plan. The IMRT and 3D-CRT plans were generated specifically for the present study. The plans were optimized without adjusting for the chemotherapy effect. The effect of chemotherapy was modeled as an independent cell killing process by considering a uniform chemotherapy equivalent radiation dose added to all voxels of the organ at risk. The risk of radiation pneumonitis was estimated for all plans using the Lyman and the critical volume models. Results For radiotherapy alone, the critical volume model predicts that the two IMRT plans are associated with a lower risk of radiation pneumonitis than the 3D-CRT plan. However, when the chemotherapy equivalent radiation dose exceeds a certain threshold, the radiation pneumonitis risk after IMRT is greater than after 3D-CRT. This threshold dose is in the range estimated from clinical chemoradiotherapy data sets. Conclusions Cytotoxic chemotherapy might affect the relative merit of competing radiotherapy plans. More work is needed to improve our understanding of the interaction between chemotherapy and the radiation dose distribution in clinical settings.