How often is a second treatment needed after HIFU if biopsy stays positive?

The short version: if the biopsy is still positive after HIFU, a second treatment is usually needed, and the number who get one is high.

A positive biopsy after HIFU is not a gray zone. In a 74-patient cohort, 15.5% had positive biopsies during follow-up, and every one of them also had biochemical failure [1]. A positive biopsy is the system telling you the cancer survived the first pass.

The larger HIFU series give the retreatment rate directly. In 1,002 patients, 254 required salvage afterwards: hormone therapy in 169, radiation in 75, and radical prostatectomy in 10 [3]. In a 540-patient series, 11.4% had a salvage radical prostatectomy or surgery, and overall about 26% received some salvage treatment [2]. In the focal-therapy review, roughly 10 to 30% of focal patients needed further treatment [4]. Those are rates for the whole treated population, not just biopsy-positive men. Among men whose biopsy is positive, expect the rate to be at the high end or higher.

The 15.5% figure [1] is biochemical failure, not "second HIFU." These series mostly report hormone therapy, radiation, or prostatectomy as the next step, not repeat HIFU. That matters for you: positive biopsy usually means the ablation missed, and a second ablation may miss again.

My call: if your biopsy is positive after HIFU, plan on needing another treatment, with substantial likelihood, and discuss the specific next option (radiation, hormone therapy, or surgery) rather than assuming a repeat HIFU will fix it. Confidence: moderate on the retreatment rate, low on how often repeat HIFU specifically is chosen over the alternatives.