ESTRO 36 Abstract Book

S925 ESTRO 36 _______________________________________________________________________________________________

Conclusion Some conventional and textural features are strongly dependent on the PET device and acquisition parameters such as voxel size. A robustness analysis should be performed before each multi-centric radiomic study, to evaluate the possibility of gathering data from different devices. Multivariate analysis showed that radiomic features can predict LACC local recurrence with a better accuracy than SUV max for recent PET devices. The creation of an external validation cohort is in progress to confirm the results. EP-1693 Functional MRI to individualize PTV margins to seminal vesicles with suspected cancer involvement S. Damkjaer 1 , J. Thomsen 1 , S. Petersen 1 , J. Bangsgaard 1 , M. Aznar 2 , I. Vogelius 1 , P. Petersen 1 1 Rigshospitalet, Department of Oncology- Section for Radiotherapy - 3994, København, Denmark 2 University of Oxford, Clinical Trial Service Unit- Richard Doll Building, Oxford, United Kingdom Purpose or Objective For external beam radiotherapy of prostate cancer patients, the information from pre-treatment MRIs can give patient specific and visual evaluation of suspected pathologically involved volumes in the seminal vesicles (SV) as an important addition to probability based nomograms [1]. We investigate the impact of individualized PTV margins around the SV based on MRI information.

Results SUV max

, SUV peak , Homogeneity and SRE computed in VOI-L were significantly different between the two devices (p<0.05). These p-values suggested that data coming from the two PET devices can therefore not be gathered. In G1, the best 4-feature signature was a combination of Entropy, SUV mean , SUV max and SRE (AUC=0.77) and in G2, a combination of SUV peak , Homogeneity, LGZE, HGZE (AUC=0.86). G2 signature was validated in G1 with AUC=0.76 and was significantly more powerful than SUV max according to Delong’s test (p=0.02). G1 signature was not validated in G2, yielding to an AUC less than that obtained with SUV max only.