Impact Of Pretreatment Whole-Tumor Perfusion Computed Tomography And (18)F-Fluorodeoxyglucose Positron Emission Tomography Measurements On Local Control Of Lung Tumor Treated With Stereotactic Body Radiation Therapy

[18F] fluorodeoxyglucose positron emission tomography (18F-FDG PET) has become widely used in diagnostic and pretreatment evaluations as well as staging for patients with malignant tumors. Maximum standardized uptake value (SUVmax) is the most widely used PET parameter, and it has been shown to have potential prognostic value in patients undergoing stereotactic body radiation therapy (SBRT) for lung tumor. In recent studies, reductions in perfusion CT parameters suggestive of hypoxic conditions within a tumor such as tumor blood volume, which is measured as the average iodine density (AID) via dual-energy computed tomography (DE-CT), have been shown to correlate with local recurrence. However, the relationship between SUVmax and AID has not yet been fully elucidated. This study aimed to investigate the correlation between the AID and SUVmax for lung tumor treated with SBRT. Between March 2011 and December 2015, 91 medically inoperable patients with 74 primary non-small cell lung cancer and 17 lung oligo-recurrence who underwent both DE-CT and 18F-FDG PET/CT before SBRT (50‒60 Gy in 5‒6 fractions) were followed up after a median interval of 21.0 months. Among the 91 patients, 8 patients had 2 lung tumors. Thus the subjects of this study had 99 lung tumors. Kaplan–Meier analysis was used to determine associations between local control (LC) and variables. Median AID and SUVmax were 18.60 (range, 1.18‒92.71) (100 μg/cm3) and 3.2 (range, 0.7‒19.7), respectively. A weak negative correlation was observed between AID and SUVmax (R = 0.205, P = 0.42). Two-year LC rates were 96.3% vs. 75.3% (P = 0.020) and 74.6% vs. 96.0% (P = 0.019) for patients classified according to high vs. low AID or SUVmax, respectively. Two-year LC rates for patients with adenocarcinoma vs. other cancers were 96.4% vs. 77.9% (P = 0.011), respectively. Multivariate analysis identified AID and histology as significant predictors of LC. Additionally, the two-year LC rate was only 54.4% in the subgroup of lower AID and higher SUVmax vs. >90% (range, 94.4‒100%) in other subgroups (P = 0.004). Despite the short follow-up period, a reduction in AID and subsequent increase in SUVmax correlated significantly with local failure in SBRT-treated lung tumor patients. Further studies involving larger populations and longer follow-up periods are needed to confirm these results.