Many men approach the question on prostate cancer with trepidation. Biopsies can be traumatic and inaccurate. Therapy such as whole prostate resection or radiation can lead to impotence and incontinence. But emerging strategies can reduce the need for biopsies and lead to focal therapy for the small prostate cancers instead of treating the whole gland.
One of them, tissue-type imaging (TTI) with ultrasound, was described at the 2008 RSNA meeting. If further studies confirm its value, this imaging technique could revolutionize the detection and treatment of prostate cancer, according to Ernest J. Feleppa, Ph.D., research director of the Frederic L. Lizzi Center for Biomedical Engineering at the Riverside Research Institute in New York City.
“The method seems to be capable of distinguishing cancerous from noncancerous tissue in the prostate,” Feleppa told Diagnostic Imaging. “This would be a major breakthrough for biopsy guidance and treatment planning and delivery.”
Feleppa is among a number of researchers who are looking for more precise ultrasound prostate tumor targeting strategies to replace today’s common systematic biopsy (see accompanying article).
Echo signals carry sound pulses that are unique to the tissue investigated by the ultrasound probe. Much of the information acquired in the original echoes is currently discarded in the process of creating a conventional image. TTI instead analyzes the echo-signal spectrum before it is converted into an image, Feleppa said.
Feleppa and study coauthor Dr. Christopher Porter used TTI to analyze the echo signals of 617 prostate regions under biopsy from 64 patients. The investigators combined the spectral characterization of the biopsy samples with prostate-specific antigen values using a computerized classification system that calculated scores for relative likelihood of cancer. After comparing TTIbased characterization with conventional B-mode interpretations of the biopsy locations, the researchers found that TTI could successfully detect cancers missed by conventional ultrasound.
No known conventional imaging modality can reliably detect prostate cancer. As a result, biopsies cannot be directed into suspicious regions but are instead systematically but “blindly” placed at predetermined sites throughout the gland, Feleppa said. The same approach happens with treatment, which usually involves the entire gland because the location of tumors cannot be pinpointed accurately.
If further research proves to validate the results obtained to date, however, biopsies would become far more accurate. TTI could bring down the false-negative biopsy rate or reduce the number of unwarranted biopsies. The method could also bolster staging, reduce side effects, and provide a reliable way to follow up treated and untreated cancers. Treatment of the whole gland could potentially give way to focalized therapy approaches.
“While some advanced MR methods show similar promise, the difference in cost, ease of clinical use, and examination time make ultrasound the preferable modality by far,” Feleppa said.
