Abstract
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Objectives The purpose of this study was to clarify the feasibility of heterogeneity analysis of intratumoral hypoxia estimated on F-18-fluoromisonidazole (FMISO) PET/CT in consideration with parameters including absolute levels of FMISO and therapeutic response in the course of RT.
Methods This study involved 18 patients (pts) with neoplasms (head and neck 8, esophagus 5, anus 2, lung 2, uterus 1) who underwent RT and FMISO PET/CT. FMISO PET/CT scans were conducted at the baseline and at 20 Gy of RT; each patient received iv injection of FMISO (7.4 MBq/kg) and underwent PET/CT at 180 min. Regions of interest were placed on tumors to measure SUVs of FMISO. Additionally, texture analyses were conducted to calculate the heterogeneity indices of skewness, kurtosis, and another heterogeneity index of area under curve of cumulative SUV histogram (AUC-CSH). And a larger skewness, a larger kurtosis, and a smaller AUC-CSH were considered to indicate a higher heterogeneity. Pts were categorized into CR and non-CR (PR+NC+PD) groups, and the parameters were compared between the two groups by Mann-Whitney’s U test.
Results Pts received chemoradiation therapy (n=17, 42-70 Gy) or RT alone (n=1, 64 Gy). Nine pts reached CR, while 9 did not. Reduced FMISO SUVs were observed at 20Gy as compared to before RT, which might correspond to reoxygenation. CR group showed statistically significant lower SUVmax and kurtosis and a tendency of lower skewness and higher AUC-CSH.
Conclusions A lower absolute level of FMISO accumulation before RT might be predictive of a better therapeutic response. Heterogeneity analysis of intratumoral FMISO distribution was feasible using indices of skewness, kurtosis, and AUC-CSH. Correlation of heterogeneity and therapeutic response should be clarified in further studies.
Research Support This work was supported by JSPS KAKENHI Grant Numbers 21591580 and 25461854.