Diagnosis of prostate cancer remains imperfect. Current methods of prostate biopsy are limited by over detection of slow-growing tumors and under detection of clinically relevant cancers. Investigators at the University of California-Los Angeles Department of Urology have found that a new technique of targeted biopsy in a clinic setting, using local anesthesia, may improve diagnosis and aid in selecting which patients are suitable for active surveillance and which need focal therapy (noninvasive techniques for destroying small tumors within the prostate). Their results are published in The Journal of Urology.
"The technology exists to biopsy prostate tumors under magnetic resonance imaging (MRI) guidance and this has been shown to improve prostate cancer diagnosis," says first author Geoffrey Sonn, MD, Department of Urology, Institute of Urologic Oncology, University of California-Los Angeles. "But such procedures are time-consuming, costly, and impractical in most settings. Magnetic resonance ultrasound (MR-US) systems that fuse stored MR images with real-time ultrasound combine the resolution of MRI with the ease and practicality of ultrasound, offering a savings in time and cost, while potentially retaining the accuracy of MR-guided biopsy. However there are further limiting factors - the need for monitored anesthesia care, or a transperineal approach and general anesthesia."
Investigators report on the findings in a group of men who underwent MR-US fusion biopsy as outpatients at the UCLA Clark Urology Center. Of the 171 men in the study, 106 underwent biopsy for surveillance, while 65 had an increased prostate specific antigen (PSA) level but previously negative biopsies. All had a median PSA of 4.9 ng/ml and a median prostate size of 48 cc. Following a procedure lasting about 20 minutes, none of the patients required hospitalization.
The researchers found that a targeted biopsy was three times more likely to identify cancer than a systematic biopsy. The biopsies showed prostate cancer in 90 of the 171 men.
"The study yielded three key findings," reports Leonard S. Marks, MD, lead investigator, professor of urology and director of the UCLA Active Surveillance Program. "First, it demonstrated the ability to target and biopsy lesions in an office-based setting with the patient under local anesthesia. Second, adding targeted biopsies to systematic biopsies increased the rate of diagnosis of all cancers and, more importantly, Gleason 7 or greater cancer. In fact, 38% of men with Gleason 7 or greater cancer had disease which was detected only by targeted biopsies of lesions detected on MRI. Third, the level of suspicion on MRI correlates with cancer diagnosis overall and diagnosis of Gleason 7 or greater prostate cancers. The biopsies revealed prostate cancer in 16 of 17 men with a grade 5 lesion on MRI."
The study shows that targeted prostate biopsy may be useful in the three key situations of active surveillance, increased PSA but negative transrectal ultrasound (TRUS) biopsy, and selection for focal therapy. It may improve patient selection, making surveillance a more attractive option for patients while reducing progression to active treatment. It may also identify tumors missed on TRUS biopsy, sparing patients the discomfort of numerous negative biopsies and reducing the risk of delayed diagnosis of aggressive tumors.
"Finally, focal therapy has become an area of keen interest. This technique can spare patients the more invasive, morbid perineal template-mapping biopsy often required for focal therapy. Two recent studies using different MR-US fusion devices yielded similar results. "This substantiates the advantages of image-guided targeted biopsy using MR-US fusion" concludes Dr. Marks.
The investigators acknowledge that due to the low risk patient population studied, relatively few patients underwent radical prostate surgery. "It remains possible that some tumors may be missed by this technique," says Dr. Marks. Further work, including a detailed study correlating MRI, targeted biopsy results, and prostatectomy specimens is ongoing.
Commenting on the study, Dr. Bradford Hood and colleagues at the National Cancer Institute, NIH, write, "MR-US fusion guided biopsy unblinds the 'blind' biopsy and has great potential to supplement or replace 'blind' TRUS prostate biopsies. However, significant hurdles remain to broad adoption and the best approach is yet to be determined."