Differential inflammatory response dynamics in normal lung following stereotactic body radiation therapy with protons versus photons

• Published in: Radiotherapy and oncology 2019-07, Vol.136, p.169-175
• Main Authors: Li, Yanjing, Dykstra, Michael, Best, Till D., Pursley, Jennifer, Chopra, Nitish, Keane, Florence K., Khandekar, Melin J., Sharp, Gregory C., Paganetti, Harald, Willers, Henning, Fintelmann, Florian J., Grassberger, Clemens
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; Carcinoma, Non-Small-Cell Lung - diagnostic imaging; Carcinoma, Non-Small-Cell Lung - radiotherapy; Dose–response relationship; Female; Humans; Inflammation - etiology; Lung - radiation effects; Lung Neoplasms - diagnostic imaging; Lung Neoplasms - radiotherapy; Male; Middle Aged; Photons - adverse effects; Photons - therapeutic use; Proton therapy; Proton Therapy - adverse effects; Radiation pneumonitis; Radiosurgery; Radiosurgery - adverse effects; Retrospective Studies; Tomography, X-Ray Computed
• ISSN: 0167-8140; 1879-0887; 1879-0887
• DOI: 10.1016/j.radonc.2019.04.004

•Unique cohort of lung cancer patients were treated with SBPT and matched to SBRT patients.•Lung inflammation increased linear with dose with no difference in maximum response.•Lung inflammation kept increasing late after SBRT, more pronounced early after SBPT. To compare time-dependent changes in lung parenchyma of early-stage non-small cell lung carcinoma (NSCLC) patients after stereotactic body radiation therapy with protons (SBPT) or photons (SBRT). We retrospectively identified NSCLC patients treated with SBPT and matched each one with a SBRT patient by patient, tumor, and treatment characteristics. Lung parenchyma on serial post-treatment chest computer tomography (CT) scans was deformably registered with the treatment plan to analyze lung density changes as function of dose, quantified by Houndsfield Unit (HU)/Gy. A thoracic radiologist also evaluated the CTs using an established grading system. We matched 23 SBPT/SBRT pairs, including 5 patients treated with both modalities (internally matched cohort). Normal lung response following SBPT significantly increased in the early time period (CTs acquired 6 HU/Gy) patients and in the internally matched cohort. However, there was no significant difference in the maximum observed response in the entire cohort over all time periods, median 3.4 [IQR, 1.0–5.4] HU/Gy (SBPT) versus 2.5 [1.6–5.2] HU/Gy (SBRT). Qualitative radiological evaluation was highly correlated with the quantitative analysis (p