New techniques promise better detection of prostate cancer

March 10, 2007

Ultrasound techniques that are improving prostate cancer detection, grading, and staging are useful in men presenting with an elevated level of prostate specific antigen. They offer therapeutic strategies and may avoid the need for prostatectomy. In the future, surgery may not be the number one treatment choice, according to speakers at a special focus session on imaging in patients with elevated PSA levels.

Ultrasound techniques that are improving prostate cancer detection, grading, and staging are useful in men presenting with an elevated level of prostate specific antigen. They offer therapeutic strategies and may avoid the need for prostatectomy. In the future, surgery may not be the number one treatment choice, according to speakers at a special focus session on imaging in patients with elevated PSA levels.

Using real-time elastography, tissues can be compressed by a probe to measure their stiffness. Studies reveal that real-time sonoelastography-targeted biopsy in a patient with cancer is 2.8 times more likely to reveal prostate cancer than systematic ultrasound-guided biopsy.

Elastography also shows potential in staging the disease. While some questions remain about its limitations in terms of cost, training, and potential delivery of false-positive results related to medication or prostatitis, the technique looks set to become another standard technique requested of the radiologist by the clinician.

Part of the battle is detection of the cancer, according to Dr. Ferdinand Frauscher of the Medical University of Innsbruck in Austria. Gray-scale ultrasound provides useful information on the anatomy and morphology of the prostate and high differentiation between the peripheral zone and the inner gland.

In the early 1980s, hypoechoic nodules were seen as the main presentation of prostate cancer, but up to 30% of all prostate cancers are isoechoic. Frauscher estimates that hypoechoic nodules have a 17% to 57% chance of being identified as prostate cancer, though since the discovery of PSA, this percentage is reported to be as low as 9%.

Gray-scale ultrasound remains a key tool for guiding biopsies and other interventions, but it misses a number of clinically relevant cancers due to its relatively low sensitivity and specificity. New methods can dramatically improve diagnosis and grading, according to Frauscher. Besides elastography, contrast-enhanced color Doppler lends weight to staging due to its ability to demonstrate vascularity.

While vascular patterns demonstrated by color Doppler flow detect advanced disease, a considerable number of cancers are missed even with high-end Doppler units. Contrast enhancement shows an increased sensitivity and specificity in studies carried out at the university hospital and increases identification of malignant lesions with higher Gleason scores.

Prostate cancer has a high incidence rates, accounting in 2003 for one in three cancers detected in the U.S. and one in five in the Netherlands. Despite an increase in prostate cancer detection since the discovery of PSA in 1991, a flat mortality rate suggests that most patients have a good chance of survival if the cancer is caught and followed through prostatectomy, radiation therapy, active surveillance, or watchful waiting.

In T1 tumors treated locally and T4s requiring radiation therapy, the tumor's exact location and size are pivotal to accurate staging and choice of therapy. Removal of a T1 is followed by an average 70% to 80% 10-year survival rate, according to Dr. Jeroen van Moorselaar, a urologist at the Vrije Universiteit Medisch Centrum in Amsterdam. These days, though, patients demand more than simply survival.

"Side effects such as incontinence and impotence, if the neurovascular bundles are cut, are no longer acceptable to many patients. The radiologist can tell the surgeon the location of the tumor in the peripheral zone, which is important for prognosis of side effects after surgery," Moorselaar said.