An exploratory study of dose escalation versus standard focal High Intensity Focused Ultrasound for treating non-metastatic prostate cancer.

Objective To compare cancer control rates of standard compared to dose escalation focal high-intensity focused ultrasound (HIFU) of prostate cancer. Materials and methods A prospectively maintained HIFU (Sonablate(R) 500) database identified 598 patients were identified who underwent focal HIFU (Sonablate(R) 500) (March/2007-November/2016). Follow-up occurred with 3-monthly clinic visits and PSA testing in the first year. Thereafter, PSA was measured 6-monthly. mpMRI with biopsy was used for MRI-suspicion of recurrence. Treatments were delivered in a quadrant or hemiablation fashion depending on the gland volume as well as tumour volume and location. Prior to mid-2015, standard focal-HIFU was used (two HIFU blocks); after this date some urologists conducted dose escalation focal-HIFU (3 overlapping HIFU blocks). Propensity matching was used to ensure two matched groups leading to 162 cases for this analysis. Treatment failure was defined by any secondary treatment (systemic therapy, cryotherapy, radiotherapy, prostatectomy, or further HIFU), metastasis from prostate cancer without further treatment, tumour recurrence with Gleason score >/=7 (>/=3+4) on prostate biopsy without further treatment, or prostate cancer-related mortality. Complications and side-effects were also compared. Results Median age was 64.5 years (IQR 60-73.5) in the standard focal-HIFU group and 64.5 years (IQR 60-69) in the dose-escalation group. Median prostate volume was 37ml (IQR 17-103) in standard group and 47.5ml (IQR 19-121) in the dose-escalation group. As tumour volume on mpMRI and Gleason score were major matching criteria these were identical with 0.43ml (IQR 0.05-2.5) and Gleason 3+3=6 in 1/32 (3%), 3+4=7 in 27/32 (84%), and 4+3=7 in 4/32 (13%). Recurrence in treated areas were found in 10/32 (31%) when standard treatment zones were applied, and in 6/32 (19%) of dose-escalation focal-HIFU (p=0.007). Conclusion This exploratory study shows that dose escalation focal-HIFU may achieve higher rates of disease control compared to standard focal-HIFU. Further prospective comparative studies are needed.