Salvage HIFU shows promise in post-RT PCa patients

High-intensity focused ultrasound as salvage therapy allows for intermediate-term disease control in selected patients with recurrence following radiation therapy for prostate cancer.

San Francisco-High-intensity focused ultrasound (HIFU) as salvage therapy allows for intermediate-term disease control in selected patients with recurrence following radiation therapy for prostate cancer.

Data from a prospective database reveal that an early predictor of recurrence-free survival in this setting is an undetectable PSA nadir achieved at a median of 3 months post-HIFU, Canadian researchers reported at the Genitourinary Cancers Symposium in San Francisco.

The data are interesting and hypothesis-generating but with the series of patients studied being relatively small, “I think that the evidence to support widespread utilization of HIFU for this indication is not there yet,” first author Shawn Dason, MD, told Urology Times. The findings “suggest that salvage HIFU may be promising as a salvage modality with reasonable intermediate-term biochemical control outcomes and limited toxicities,” added Dr. Dason, a urology resident at McMaster University, Hamilton, Ontario, working with Bobby Shayegan, MD, and colleagues.

Local failure rates are as high as 32% following electron beam radiation therapy for prostate cancer, and one-third of patients receiving 81Gy radiotherapy have positive biopsies. To date, local salvage options include salvage prostatectomy, cryotherapy, and brachytherapy. Dr. Dason’s group investigated HIFU in 24 patients with localized radio-recurrent prostate cancer, defined as both a PSA nadir + 2 ng/mL and a positive biopsy.

Study participants were treated with a single session of whole-gland HIFU ablation, with the primary endpoint being recurrence-free survival, defined as a composite endpoint of PSA progression, receipt of any further salvage therapy, receipt of androgen deprivation therapy, clinical progression, or death.

Median PSA level at study entry was 4.02 ng/mL. The treated prostate volume was 23.8 cc. Median follow-up was 31 months. Many patients experienced a sizable decline in PSA from HIFU, with three being PSA non-responders. The median time to PSA nadir was 3 months after treatment, and the median post-HIFU PSA nadir was 0.04 ng/mL.

The 2-year and 5-year recurrence-free survival rates were 66.3% and 51.6%, respectively.

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An undetectable PSA nadir was a strong predictor of recurrence-free survival (HR 0.07; 95% CI: 0.02 to 0.29; p<.001).

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Who benefits from which modality unknown

No comparative data exist between the different forms of nonsurgical salvage therapies, said Dr. Dason, and which patients specifically would benefit from each modality is not certain.

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“The reality is that the use of any one of these modalities for salvage therapy will depend on availability. All of these therapies should really only be administered as part of an experimental protocol since the data we have on toxicities and long-term outcomes is not mature enough for widespread adoption,” Dr. Dason said.

While all nonsurgical options avoid the medical risks of surgery and seemingly have lower rates of rectal injury and incontinence, some toxicities appear to be unique after nonsurgical therapies, such as rectourethral fistulae and osteitis pubis.

Urethral strictures are seen with both surgical and nonsurgical therapies, but are probably more common with the latter, he said. In the series presented here, the rate of toxicity was low, with no rectal complications and no cases of osteitis pubis.

“Other series have reported these complications after salvage HIFU but also suggest that they are rare. These findings suggest that salvage HIFU may be promising as a salvage modality with reasonable intermediate-term biochemical control outcomes and limited toxicities,” Dr. Dason said.

In looking at absolute numbers, the biochemical recurrence-free survival in this small series appears to be similar to published series on salvage prostatectomy and other nonsurgical salvage options, he indicated.

“Future randomized controlled trials will be important in confirming these promising results,” he said.