External beam radiation doesn’t always eradicate prostate cancer. Researchers estimate that about 20% to 30% of patients experience a rising prostate-specific antigen (PSA), or biochemical recurrence of their disease, following treatment. Debate about what secondary, or salvage, treatment to try next has blossomed.
High-intensity focused ultrasound (HIFU), which uses sound waves to destroy cancerous tissue, is one option for treating a localized recurrence (see Figure 1 below). Because each pulse of energy ablates only a small amount of tissue, doctors can target certain areas and spare others, theoretically minimizing the chances of side effects.
Figure 1: High-intensity focused ultrasound (HIFU)
During HIFU, pulses of energy produced by a rectal probe destroy tissue at the point where sound waves converge. Because the technology can target certain areas and spare others, side effects may be minimized.
British researchers recently examined the effectiveness of HIFU in 31 men who experienced a biochemical recurrence of prostate cancer following external beam radiation. Prior to HIFU, the average PSA among the men was 7.7 ng/ml. Three months after HIFU, about 65% had a PSA of 0.2 ng/ml or less. Of those who reached the six- and nine-month check-ups, about half maintained a PSA at that level.
Side effects of HIFU included narrowing of the urethra and the need for a procedure to remove dead tissue, urinary tract infections, painful urination, urinary incontinence, and, rarely, the formation of a hole between the rectum and urethra. The chance of side effects was on a par with that of other salvage treatments, making HIFU a seemingly feasible option.
Choosing appropriate patients for salvage HIFU remains the biggest challenge, the researchers noted. HIFU will not effectively treat metastatic cancer, but some patients harbor cancer that has spread elsewhere in the body and evades detection prior to HIFU.
SOURCE: Zacharakis E, Ahmed HU, Ishaq A, et al. The Feasibility and Safety of High-Intensity Focused Ultrasound as Salvage Therapy for Recurrent Prostate Cancer Following External Beam Radiation Therapy. BJU International 2008;102:786–92. PMID: 18564135.
Originally published April 1, 2009; last reviewed March 31, 2011.