Article

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

¹ IRSN, Laboratoire d’Evaluation de la Dose Interne, 92262 Fontenay-aux-Roses, France.
² Hôpital Européen Georges Pompidou, Service de médecine nucléaire, 75015 Paris, France.
³ UPMC, Univ. Paris 06 Bio physics, 75005 Paris, France.
⁴ Hôpital Trousseau, Service de médecine nucléaire, 75012 Paris, France.

^* aurelie.desbree@irsn.fr

Received: 4 April 2014
Accepted: 30 July 2014

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 ^99mTc-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,healthyliver} 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 two-fraction 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.