We assessed the potential benefits of including systematic 18 fluorodeoxyglucose positron emission tomography (FDG-PET) for detecting tumour recurrence in a prospective randomised trial. Patients (N ¼ 130) who had undergone curative therapy were randomised to undergo either conventional (Con) or FDG-PET procedures during follow-up. The two groups were matched at baseline. Recurrence was confirmed histologically. 'Intention-to-treat' analysis revealed a recurrence in 46 patients (25 in the FDG-PET group, and 21 in the Con group; P ¼ 0.50), whereas per protocol analysis revealed a recurrence in 44 out of 125 patients (23 and 21, respectively; P ¼ 0.60). In another three cases, PET revealed unexpected tumours (one gastric GIST, two primary pulmonary cancers). Three false-positive cases of FDG-PET led to no beneficial procedures (two laparoscopies and one liver MRI that were normal). We failed to identify peritoneal carcinomatosis in two of the patients undergoing FDG-PET. The overall time in detecting a recurrence from the baseline was not significantly different in the two groups. However, recurrences were detected after a shorter time (12.1 vs 15.4 months; P ¼ 0.01) in the PET group, in which recurrences were also more frequently (10 vs two patients) cured by surgery (R0). Regular FDG-PET monitoring in the follow up of colorectal cancer patients may permit the earlier detection of recurrence, and influence therapy strategies.

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-For targeted radionuclide therapies, treatment planning usually consists of the administration of standard activities without accounting for the patient-specific activity distribution, pharmacokinetics and dosimetry to organs at risk. The OEDIPE software is a user-friendly interface which has an automation level suitable for performing personalized Monte Carlo 3D dosimetry for diagnostic and therapeutic radionuclide administrations. Mean absorbed doses to regions of interest (ROIs), isodose curves superimposed on a personalized anatomical model of the patient and dosevolume histograms can be extracted from the absorbed dose 3D distribution. Moreover, to account for the differences in radiosensitivity between tumoral and healthy tissues, additional functionalities have been implemented to calculate the 3D distribution of the biologically effective dose (BED), mean BEDs to ROIs, isoBED curves and BED-volume histograms along with the Equivalent Uniform Biologically Effective Dose (EUD) to ROIs. Finally, optimization tools are available for treatment planning optimization using either the absorbed dose or BED distributions. These tools enable one to calculate the maximal injectable activity which meets tolerance criteria to organs at risk for a chosen fractionation protocol. This paper describes the functionalities available in the latest version of the OEDIPE software to perform personalized Monte Carlo dosimetry and treatment planning optimization in targeted radionuclide therapies.

-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.