## 3 Results  
S Sixty-five patients underwent [18]FJtuciclovine PET/CT between March 2021 and August 2022. Overall, 36/65 patients were excluded (Figure 2) because their follow-up period was \(<\)3 months or because medical records for them were missing (23/36 patients); because their [18]FJtuciclovine scan was performed on a prior PET/CT tomograph (6/36 patients);  
Figure 1: Example of LIFEx platform tools used to extract radiomics features from [F18]Fluciclovine PET/CT scan drawing a manual 3D region of interest (ROI) on DICOM-converted images. One hundred and fourteen radiomic features (RFs) were extracted for each ROI. Thirteen robust RFs were tested on our sample. because they could not be contacted to ensure we had complete medical records for them (5/36 pts); or because no uptake foci were detectable on their [18F]Flucicolovine scan and no RFs could be extracted (2/36 pts). Finally, 29 patients with locoregional recurrence were included in this analysis. In Table 1, medical records of the population included are shown. Follow-up in our population spanned 8.6 \(\pm\) 4.8 months (mean \(\pm\) SD). Overall, 10/29 patients biochemically relapsed 10 years after the first curative Pca approach. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Age at Diagnosis (yo, Mean \(\pm\) SD)** & \multicolumn{2}{c}{**66 \(\pm\) 7**} \\ \hline
**Gleason Score** & **No. Patients** & **\%** \\ \hline nd & 1 & 3 \\ \hline
3 + 2 & 2 & 6 \\ \hline
3 + 3 & 6 & 19 \\ \hline
3 + 4 & 12 & 39 \\ \hline
3 + 5 & 1 & 3 \\ \hline
4 + 3 & 5 & 16 \\ \hline
4 + 4 & 2 & 6 \\ \hline
4 + 5 & 1 & 3 \\ \hline
5 + 3 & 1 & 3 \\ \hline PSA at diagnosis (mean \(\pm\) SD) 14.25 \(\pm\) 14.9 ng/mL & \\ \hline \(<\)4 ng/mL & 2 & 6 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Medical records (mean \(\pm\) SD) of the 29 patients included in the study. Figure 2: Flowchart showing patients included in the present study. PSA levels, registered both at diagnosis and before [18F]Fluciclovine PET/CT, did not predict the outcome (data not shown). [18F]Fluciclovine revealed significant focal uptake in the prostatic bed or in Douglas' space. In 4/29 patients, however, [18F]Fluciclovine also imaged six bone foci of uptake, interpreted as metastatic and confirmed at follow-up (Figure 3). These four findings were not included in the radiomic signature analysis. Textural records of the 29 patients enrolled in this study are shown in Table 2. \begin{table}
\begin{tabular}{c c c} \hline
**Age at Diagnosis (yo, Mean \(\pm\) SD)** & \multicolumn{2}{c}{**66 \(\pm\) 7**} \\ \hline
**Gleason Score** & **No. Patients** & **\%** \\ \hline
4 \(\div\) 10 ng/mL & 15 & 48 \\ \hline \(>\)10 ng/mL & 13 & 42 \\ \hline PSA at fluciclovine PET/CT & & \\ \hline \(<\)1 ng/mL & 12 & 39 \\ \hline \(1\div\) 2 ng/mL & 9 & 29 \\ \hline \(>\)2 ng/mL & 9 & 29 \\ \hline \multicolumn{3}{c}{Time to relapse (years)} \\ \hline \(<\)1 year & 4 & 13 \\ \hline \(1\div\) 3 years & 7 & 23 \\ \hline \(3\div\) 5 years & 2 & 6 \\ \hline \(5\div\) 10 years & 8 & 26 \\ \hline \(>\)10 years & 10 & 32 \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._  
Figure 3: Maximum intensity projection (**a**), [18F]Fluciclovine PET (**b**), and PET/CT (**c**) axial view of locoregional recurrence of Pca (green arrow), as seen in our series in a patient (61 yo). This recurrence occurred 6 years after radical prostatectomy, PSA 1.34 ng/mL. In (**d**), a bone focus of [18F]Fluciclovine uptake, interpreted as metastasis, on the right pedicle of L4 (red arrow) in the same patient is shown, which was then confirmed by MR (**e**). After [18F]Flucicolovine PET/CT, the therapeutic approach progressed from antiandrogenic therapy to abiterarone or to radiation therapy in 29/29 patients. Our univariate analysis found four IBSI features to be significant; two were of the histogram intensity type, i.e., generated by discretizing the original set of gray levels into gray-level bins, and the other two were of the GLSZM (Gray-Level Size Zone Matrix) type, which counts the number of groups of linked voxels.