A modified equivalent uniform dose with the dosimetric parameters of perfusion imaging correlates with radiation pneumonitis in radiation therapy planning / 中国癌症杂志

ABSTRACT

Background and purpose: The literature on dose-volume parameters and pneumonitis is extensive. The results are inconsistent, both for the best predictive metrics and significant comorbid factors. This study aimed to investigate a prospective functional equivalent uniform dose (fEUD) with perfusion single photon emission computed tomography (SPECT) images as predictors of radiation pneumonitis (RP) in patients undergoing curative radiotherapy (RT). Methods: Functional lung imaging was performed using SPECT for perfusion imaging. Perfusion factors were defined as the mean percentile perfusion levels of the 4 areas, top to 75%, 75% to 50%, 50% to 25%, 25% to 0%, re-spectively. fEUD was calculated from perfusion factors and standard dose-volume parameters extracted from treatment planning computed tomography (CT) scans. Total lung (TL), ipsilateral (IL) and contralateral lung (CL) volumes minus gross tumor volume (GTV), whole-lung V5, V20, whole lung fEUD, IL and CL fEUD, and general equivalent uniform dose (gEUD) were analyzed to evaluate correlations between RP using Common Terminology Criteria for Adverse Events (CTCAE) version 4.03. Statistical significance was defined as P<0.05. Results: A total of 15 patients treated with intensity modulated RT or 3D conformal RT were analyzed, grades≥3 RP were observed in 6 patients. There was only a trend toward significance for unilateral (UL) fEUD of higher dose side (P=0.007). Whole-lung V5, V20 were almost identical between patients who developed pneumonitis and patients who did not, as the values were below the recommended thresholds from published papers. Unilateral fEUDs were linear with unilateral gEUDs (t=0.815, P=0.000). Conclusion: SPECT-based equivalent uniform dose appears to be a better predictor of RP compared to stan-dard dose-volume parameters. Planning constraints should aim to keep unilateral fEUD below 21 Gy.