Prostate cancer treated with irreversible electroporation: MRI-based volumetric analysis and oncological outcome

Background: To assess multiparametric magnetic resonance imaging (mpMRI) characteristics in prostate cancer (PCa) before and after irreversible electroporation (IRE) and to investigate their correlation with the presence of post-operative recurrence of PCa.

Methods: MpMRI was performed in 30 men with PCa prior to treatment, after 10 days and at 6 months. An additional scan at 1 year was available for 18 men. Two radiologists assessed retrospectively the following parameters by planimetry: tumour volume, necrotic volume (early post-treatment scan) and residual fibrosis. Residual tumour/recurrence were defined as a suspicious area within the treatment field scored ≥ 4 on a 1-to-5 scale. Oncological outcome was also assessed.

Results: The median follow-up of the entire study was 16 months. Six men were undertreated and showed mpMRI recurrence after 6 months. At 1-year, three additional men had recurrence. Overall, four of these 9 men (44%) were retreated. The other five men did not receive any further treatment. Median time to re-treatment was 15 months. Median pre-treatment lesion volume was 0.65 cc, 0.66 cc and 0.43 cc on the different mpMRI sequences (T2-weighted, diffusion-weighted and dynamic contrast enhanced imaging). Median necrotic volume was 10.77 cc. Median overall residual fibrosis volumes were 0.84 cc and 0.95 cc at 6-month and 1-year mpMRI. Pre-treatment, necrotic and residual fibrosis volumes were significantly different (p < 0.001). Pre-treatment tumour volumes on diffusion-weighted imaging and necrotic volumes were correlated (r = 0.18; p = 0.02).

Conclusions: MpMRI is able to visualise the IRE ablation effects in men with PCa. MpMRI-derived parameters - such as tumour, necrotic and fibrosis volumes - can be measured and are potentially useful for assessing efficacy in the medium term, as with other ablative techniques.