Fractionation protocol design for treatment planning optimization in SIRT using the OEDIPE software

Abstract

-To go further in the optimization of treatment planning in selective internal radiation therapy (SIRT), radiobiological aspects can be accounted for with the OEDIPE software and used to design fractionation protocols. Dosimetry was performed using data from 99m Tc-MAA evaluations of 10 patients treated for hepatic metastases with SIRT. The maximal injectable activity (MIA) was calculated, using a tolerance criterion on BED mean,healthy liver equal to 54 Gy 2.5 , for different fractionation protocols, varying the number of fractions, the repartition of activity and the time delay between fractions. OEDIPE was also used to calculate BED mean and the EUD to the tumoral liver (TL) that would be delivered with those MIAs. Compared with a single-injection protocol, the MIA is increased on average by 23% ± 3%, 36% ± 5% and 45% ± 7% for fractionation protocols with 2, 3 and 4 equal fractions, respectively, while BED mean,TL is increased by 15% ± 2%, 23% ± 4% and 29% ± 5%. EUD TL , calculated for one evaluation, is increased by 51%, 115% and 159% using 2, 3 and 4 equal fractions, respectively. For this evaluation, the optimal activity repartition for twofraction protocols is (3/4 − 1/4) for time delays of less than 4 days, (2/3 − 1/3) for time delays between 4 and 6 days and (1/2 − 1/2) for time delays superior to 6 days. Finally, this study confirmed that OEDIPE can be regarded as a tool for treatment planning optimization and fractionation protocol design in SIRT.

Selective internal radiation therapy of hepatic tumors: Morphologic and functional imaging for voxel-based computer-aided dosimetry

“…Although several recommendations have been made to avoid over-or under- irradiation during radionuclide therapy, and accumulating data about the treatment optimization after personalized dosimetry have become available [ 6 ], only a few studies have described the implementation of dosimetric software in clinical routine protocols [ 4 , 7 – 11 ]. Furthermore, only a small part of these studies uses commercially available software for the internal dose estimation of the tumoral, lobar, or whole liver absorbed doses based on SPECT/CT and/or PET/CT [ 4 , 8 , 9 ].…”