Extra-target low-risk prostate cancer: implications for focal high-intensity focused ultrasound of clinically significant prostate cancer

Purpose To analyse the impact of the presence of extra-target non-clinically significant cancer (NCSC) after high-intensity focused ultrasound (HIFU) hemiablation on oncological results. To analyse radical treatment free survival (RTFS) rates at 2-3years follow-up. Methods Retrospective single-centre study of 55 patients treated by primary HIFU hemiablation from 2010 to 2016. Inclusion criteria were unilateral MRI detected CSC, stage T2b, Gleason score (GS) 7, at least 6mm distant from prostate apex. MRI with systematic and targeted biopsies was performed at diagnosis. Follow-up included clinical examination, PSA every 6 month, MRI and biopsies at 1 year and in case of PSA elevation. HIFU retreatment was possible. Whole-gland treatment was indicated in case of positive biopsies with GS 7 or maximum cancer core length >5mm, any GS. Results Mean follow-up was 33 months (SD: 17-49 months). Presence or not of an extra-target NCSC in the untreated part of the gland had no impact on RTFS at univariate analysis (p=0.29). 10 (18%) patients had a salvage whole-gland treatment after a median follow-up of 26 months (IQR 17-28). RTFS at 2 and 3years were 92% and 80%. Conclusion Presence or not of an extra-target NCSC in the untreated part of the gland had no impact on RTFS. NCSC lesion can be left untreated and actively monitored. RTFS was 80% at 3years which support the concept of focal/partial treatment as a treatment option of CSC prostate cancer.