Radiation pneumonitis: correlation of toxicity with pulmonary metabolic radiation response.
OBJECTIVE
To characterize the relationship between radiation pneumonitis (RP) clinical symptoms and pulmonary metabolic activity on post-treatment [(18)F]-fluorodeoxyglucose positron emission tomography (FDG-PET).


METHODS
We retrospectively studied 101 esophageal cancer patients who underwent restaging FDG-PET/computed tomography imaging 3-12 weeks after completing thoracic radiotherapy. The National Institutes of Health Common Toxicity Criteria, version 3, was used to score the RP clinical symptoms. Linear regression was applied to the FDG-PET/computed tomography images to determine the normalized FDG uptake vs. radiation dose. The pulmonary metabolic radiation response (PMRR) was quantified as this slope. Modeling was performed to determine the interaction of PMRR, mean lung dose (MLD), and the percentage of lung receiving >20 Gy with RP outcomes.


RESULTS
Of the 101 patients, 25 had Grade 0, 10 had Grade 1, 60 had Grade 2, 5 had Grade 3, and 1 had Grade 5 RP symptoms. Logistic regression analysis demonstrated that increased values of both MLD and PMRR were associated with a greater probability of RP clinical symptoms (p = 0.032 and p = 0.033, respectively). Spearman's rank correlation found no association between the PMRR and the dosimetric parameters (planning target volume, MLD, percentage of lung receiving >5-30 Gy). Twofold cross-validation demonstrated that the combination of MLD and PMRR was superior to either alone for assessing the development of clinical RP symptoms. The combined MLD (or percentage of lung receiving >20 Gy) and PMRR had a greater sensitivity and accuracy (53.3% and 62.5%, respectively) than either alone.


CONCLUSIONS
The results of this study have demonstrated a significant correlation between RP clinical symptoms and the PMRR measured by FDG-PET/computed tomography after thoracic radiotherapy.
Hart
Justin P
JP
Department of Radiation Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
McCurdy
Matthew R
MR
Ezhil
Muthuveni
M
Wei
Wei
W
Khan
Meena
M
Luo
Dershan
D
Munden
Reginald F
RF
Johnson
Valen E
VE
Guerrero
Thomas M
TM
D000328:Adult; D000368:Aged; D003198:Computer Simulation; D004307:Dose-Response Relationship, Radiation; D004938:Esophageal Neoplasms / Q000150:complications / Q000000981:diagnostic imaging / Q000378:metabolism / Q000532:radiotherapy; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000528:radiation effects*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011829:Radiation Dosage; D017564:Radiation Pneumonitis / Q000000981:diagnostic imaging* / Q000209:etiology / Q000378:metabolism*; D011877:Radionuclide Imaging; D011878:Radiotherapy / Q000009:adverse effects*; D013223:Statistics as Topic