Three-dimensional (3D) biopsies find more prostate cancers, particularly in the anterior regions, than those guided by ultrasound, according to a new clinical study.

Ultrasound-guided biopsies miss prostate cancers that are detected by the slightly more expensive and slightly more invasive 3D mapping biopsies. For example, in a 2006 study of 180 men diagnosed with early-stage prostate cancer via ultrasound-guided biopsy, nearly one-quarter were upgraded to a more clinically significant stage of disease after 3D mapping biopsy found pockets of cancer that the first technique had missed.

“There are three major reason[s] we perform these 3D mapping biopsies in the clinic: first, a man may have rising PSA despite a series of negative biopsies and so want[s] a more detailed opinion; second, a man may prefer additional reassurance that watching and waiting rather than treatment is the best course of action; and third, a man may pursue focal therapy in which only the cancerous sections of the prostate are removed and so need[s] accurate information on the position of his cancer,” said senior author Al Barqawi, MD, investigator at the University of Colorado Cancer Center in Aurora.

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Barqawi is a pioneer of the 3D mapping biopsy technique, in which needle biopsies are taken 5 mm apart across the x, y, and z axes of a 3D grid through the prostate, and has performed more than 600 of these procedures. The research was published in Advances in Urology (2014; doi:10.1155/2013/249080).

The current study enrolled 161 men with a mean age of 61.6 years, who had low-stage prostate cancer diagnosed by ultrasound-guided biopsy. The study performed 3D mapping biopsies at a mean of 192 days after the first biopsy and compared the results. Overall, ultrasound-guided biopsy found an average of 1.38 cancerous zones per patient, whereas 3D mapping biopsy found nearly three times the number of positive zones, at 3.33 per patient.

The follow-up findings from the 3D-mapping study resulted in upgrading the severity of many of these seemingly low-grade cancers. Specifically, after first biopsy, 7.5% of patients had been graded Gleason 7, which is considered “medium risk” and for which treatment is a reasonable option. After second biopsy, 25% were Gleason 7. After first biopsy, no patients had been scored above Gleason 7, and after 3D mapping biopsy, 4% were found to have Gleason 8, and 2% had Gleason 9.

Of these 161 total cases, cancer was found in the left midsection of the prostate 62 times after it had been missed by ultrasound-guided biopsy. Likewise, 3D mapping found 62 unreported cancers in the right midsection and 41 undetected cancers in the left-apex zone.

“This study adds to our knowledge about the interface and best uses of these two techniques. The cost and invasiveness of 3D mapping biopsy make it inappropriate for screening, but our message is that, with the confirmation or strong suspicion of cancer, 3D mapping biopsy offers a much more accurate assessment of the location, stage, and risk,” Barqawi said.