Impact of tumour invasion on seminal vesicles mobility in radiotherapy of prostate cancer

Abstract gepubliseerd in Elsevier: For patients with intermediate- and high risk prostate cancer, treated with high dose radiotherapy, the CTV generally involves the prostate and (part of) the seminal vesicles (SV) [1,2]. Fiducial markers locate the prostate reliably during radiotherapy [3]. However the SV may move independent from the corpus of the prostate [4–6]. As this should be incorporated in the PTV margin [4,6–8], this may lead to a larger irradiated rectum volume and more gastro-intestinal toxicity [9]. Several studies have shown that rectal and bladder filling are of influence on prostate and SV mobility [10–13]. Using a dietary protocol or applying rectal gas removal could somewhat decrease the prostate and SV mobility [14,15], however, these methods are not very patient friendly. In this study we hypothesize that the vesicles become more rigidly attached to the prostate in case of tumour infiltration. This would imply that in case of extensive infiltration, the prostate and vesicles move as a rigid body and are thus adequately localized by marker-based Image Guided Radiotherapy (IGRT). The aim of this study was to assess the impact of tumour invasion in the SV on their mobility.