Radiation pneumonitis is a major dose-limiting complication in thoracic radiation therapy (RT) and presents clinically in the first few months after RT. We evaluated the feasibility of quantifying pulmonary parenchymal glycolysis (PG) as a surrogate of global lung inflammation and radiation-induced pulmonary toxicity using a novel semiautomatic lung segmentation technique in non-small-cell lung cancer (NSCLC) patients and compared PG in patients treated with photon or proton RT.
We evaluated 18 consecutive locally advanced NSCLC patients who underwent pretreatment and post-treatment 18F-FDG PET/CT treated with definitive (median: 66.6 Gy; 1.8 Gy fractions) photon or proton RT between 2010 and 2014. Lung volume segmentation was conducted using 3D Slicer by performing simple thresholding. Pulmonary PG was calculated by summing 18F-FDG uptake in the whole lung.
In nine patients treated with photon RT, significant increases in PG in both ipsilateral (mean difference: 1400±510; P=0.02) and contralateral (mean difference: 1200±450; P=0.03) lungs were noted. In nine patients treated with proton therapy, no increase in pulmonary PG was observed in either the ipsilateral (P=0.30) or contralateral lung (P=0.98).
We observed a significant increase in global lung inflammation bilaterally as measured by quantification of PG. However, no significant change in global lung inflammation was noted after proton therapy. Future larger studies are needed to determine whether this difference correlates with lower risks of radiation pneumonitis in NSCLC patients treated with proton therapy.
aDepartment of Radiation Oncology, University of Maryland Medical Center
bDepartment of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland
cDepartment of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania
dDepartment of Radiation Oncology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California
eDepartment of Radiation Oncology, Northwestern University, Chicago, Illinois, USA
* Charles B. Simone II and Abass Alavi contributed equally as co-senior authors.
Correspondence to Charles B. Simone II, MD, New York Proton Center, 225 East 126th Street, NY, New York 10035, USA Tel: +1 212 646 813 1880; fax: +1 212 410 328 5279; e-mail: email@example.com
Received July 29, 2018
Received in revised form January 31, 2019
Accepted February 1, 2019