Predicting Biochemical Failure in Irradiated Patients With Prostate Cancer by Tumour Volume Measured by Multiparametric MRI

Abstract

Background/Aim: We examined the prognostic value of intraprostatic gross tumour volume (GTV) as measured by multiparametric MRI (mpMRI) in patients with prostate cancer following (primary) external beam radiation therapy (EBRT). Patients and Methods: In a retrospective monocentric study, we analysed patients with prostate cancer (PCa) after EBRT. GTV was delineated in pre-treatment mpMRI (GTV-MRI) using T2-weighted images. Coxregression analyses were performed considering biochemical failure recurrence-free survival (BRFS) as outcome variable. Results: Among 131 patients, after a median follow-up of 57 months, biochemical failure occurred in 27 (21%). GTV-MRI was not correlated with % of positive biopsy cores, Gleason score and initial PSA (all r<0.2) and only moderately correlated with cT stage (r=0.32). In univariate analysis, cT stage, Gleason score and GTV-MRI were higher in subjects with shorter BRFS (p<0.05). GTV-MRI remained a significant predictor for BRFS in multivariate analyses, independent of Gleason score and cT stage. Conclusion: GTV, defined using mpMRI, provides incremental prognostic value for BRFS, independent of established risk factors. This supports the implementation of imaging-based GTV for riskstratification, although further validation is needed.For patients with primary prostate cancer (PCa), an accurate risk stratification is mandatory to select a suitable treatment. The National Comprehensive Cancer Network riskclassification system for primary PCa patients lists clinical T stage (cT stage), Gleason score, the percentage of positive biopsy cores (PPBC) and initial prostate-specific antigen (iPSA) levels as important factors (1). Each has been shown to be an independent risk factor of biochemical failure after definitive radiotherapy (RT) (2). However, this model does not always predict the final outcome and its predictions may be very heterogeneous (3). Consequently, more robust riskfactors are urgently needed.The implementation of multiparametric magnetic resonance imaging (mpMRI) shows promising results in the delineation of the intraprostatic gross tumour volume (GTV) and is considered as the standard of care diagnostic imaging modality for patients with primary PCa (1). Three studies examined whether local recurrences of PCa after primary RT occur at the location of the primary lesion using pre-and post-treatment MRI in a limited number of patients. Each 3473 This article is freely accessible online.