Inter-observer Variability in the Segmentation of Prostate Tumour Lesions Using Multiparametric MRI (VARIOP)

Following the major technological and scientific advances in external radiotherapy in recent decades, thanks to the use of three-dimensional conformal techniques combined with intensity modulation, image-guided radiotherapy has enabled radiotherapists to increase doses without increasing sequelae and complications, giving rise to the term "dose escalation". Following multiple dose-escalation clinical trials showing better biological control of PSA, the results of the latest phase 3 FLAME trial incorporated the notion of intraprostatic boost in relation to the primary prostate lesion, considered to be the preferred site of neoplastic recurrence in prostate cancer. One of the issues raised by such a study is the methodology used to contour the tumour lesion, an issue which concerns the whole field of radiotherapy. The reference imaging technique for diagnosing prostate cancer, and more specifically the dominant tumour lesion, is multiparametric Magnetic Resonance Imaging. This leads to the first question, which concerns the identification of the dominant lesion and its precise delimitation. This last point is subject to variation between operators. A retrospective cohort from the Finistère region will therefore be used to develop a number of study points relating to : inter-operator contour variability * Factors influencing contour * Impact of contour variability on dosimetry * Automatic segmentation