MR/TRUS fusion biopsy targets high-risk prostate cancer

Targeted prostate biopsies guided by fused MR and transrectal ultrasound (TRUS) images can detect more cases of aggressive prostate cancer than traditional systematic biopsies guided by TRUS alone, according to a multicenter study published recently in Urologic Oncology: Seminars and Original Investigations.

In a two-year retrospective analysis conducted at the University of Texas (UT) Southwestern Medical Center in Dallas and Hospital Israelita Albert Einstein in São Paulo, MRI/TRUS fusion biopsy detected 11% more patients with clinically significant cancers and, notably, 16% fewer cases of low-risk cancer. What's more, the results were replicated across the two academic medical centers with diverse imaging protocols, biopsy devices, and operators.

"In light of these results, urologists need to strongly consider the use of multiparametric MRI in men with suspected prostate cancer (i.e., those with elevated and/or rising [prostate-specific antigen (PSA) levels], with or without previous negative biopsies) or with known cancer (e.g., active surveillance patients) when there is concern for progression/aggressive disease," said co-author and UT Southwestern radiologist Dr. Daniel Costa.

Challenges with prostate cancer

Despite being the most common noncutaneous cancer in men and the second most common cause of cancer-related death, prostate cancer is commonly disregarded as a not-so-important cancer, and it's surrounded by controversies such as the use of PSA for screening, Costa said.

"One of the challenges in men with known or suspected prostate cancer includes identifying patients with aggressive forms of the disease -- sometimes referred to as clinically significant prostate cancer -- while avoiding the detection of the low-risk, indolent forms that might lead to overtreatment," he said in a conversation with AuntMinnie.com. "That is where our previous clinical experience has shown that imaging can play an important aspect; this became a strong motivation for our group."

Over the past three years, a close collaboration between the institution's departments of urology (Dr. Claus Roehrborn, Dr. Yair Lotan, and Brad Hornberger), radiology (Costa, Dr. Ivan Pedrosa, and Dr. Neil Rofsky), and pathology (Dr. Franto Francis, PhD, and Dr. Payal Kapur) resulted in a successful targeted prostate biopsy program, Costa said.

To calculate the incremental diagnostic value of targeted biopsies, the researchers from UT Southwestern and Hospital Israelita Albert Einstein retrospectively reviewed the cases of 389 men with suspected prostate cancer at their two centers between February 2013 and January 2015. All patients had received multiparametric prostate MRI followed by systematic 12-core biopsy and then targeted MRI/TRUS fusion biopsy that generally consisted of two to three cores from each target (Urol Oncol, September 2016, Vol. 34:9, pp. 416.e9-416.e14).

MRI studies were performed on 3-tesla scanners and included T2-weighted imaging, diffusion-weighted imaging, and dynamic contrast-enhanced imaging. At one center, the exams were performed using either an Ingenia or Achieva scanner (Philips Healthcare) with a phased-array coil and an endorectal coil. Studies at the second center were performed on a Magnetom Trio system (Siemens Healthineers) with a phased-array coil but without an endorectal coil.

Targets for fusion biopsy

One of six radiologists at the first center and one of three radiologists at the second center had prospectively and independently read each study and assigned a Likert scale score for each lesion to reflect the suspicion of cancer risk. The radiologists at the first center had a median level of eight years of experience (range: 1-20 years) and the radiologists at the second center had a median level of seven years of experience with advanced training in body MRI. Lesions with a Likert score of at least 3 were defined as targets for MRI/TRUS fusion biopsy.

These targeted biopsies were performed using a variety of MRI/TRUS fusion systems. An elastic registration system (Urostation, Koelis) was used at the first center, while the second center used three different rigid registration systems: MyLab 60 (Esaote), Aplio 500 Smart Fusion (Toshiba Medical Systems), and Logiq E9 VNav (GE Healthcare).

One of four urologists with a median level of 13 years of experience (range: 10-23 years) with TRUS biopsies and three years of experience with targeted MRI/TRUS fusion biopsies (range: 1-3 years) performed the targeted biopsies at the first center. The targeted biopsies were performed at the second center by one of nine radiologists with a median of nine years of TRUS biopsy experience (range: 5-15 years) and two years with targeted MRI/TRUS fusion biopsies (range: 2-2 years). These were performed at both locations with the patient in the left lateral decubitus position using endocavitary 4- to 9-MHz broadband curved array end-fire transducers with an 18-gauge side-notch cutting core biopsy needle.

Fewer cancers, but more high-risk cases

Overall, targeted biopsy detected fewer cases of prostate cancer than systematic biopsy, but it detected 33 cancers that would have been missed if only systematic biopsy were performed:

• Targeted biopsy: 182/389 (47%)
• Systematic biopsy: 202/389 (52%)
• Combination of targeted and systematic biopsy: 235/389 (60%)

The researchers also found that the rate of positive findings with targeted biopsy increased in line with higher Likert scores, indicating a correlation with higher prebiopsy suspicion of prostate cancer risk. This increase was statistically significant (p < 0.0001).

Compared with systematic biopsy, targeted biopsy diagnosed more intermediate- to high-risk cancers, as well as fewer low-risk tumors, according to the researchers.

Both differences were statistically significant (p < 0.0001).

"Our research has shown that this technique improves the detection of clinically significant prostate cancer," Costa said. "We were positively surprised to also demonstrate the robustness and consistency of this diagnostic approach, with these results replicated when using different imaging protocols, different image fusion devices, various radiologists, and urologists with different levels of expertise."

Future work

The researchers are continuing to study this topic to better understand which patient groups benefit the most from the MRI/TRUS fusion biopsy and, just as importantly, which do not, Costa said.

At UT Southwestern, patients who receive multiparametric MRI of the prostate are fairly evenly divided between five groups: biopsy-naïve men with suspected prostate cancer; patients with elevated and/or rising PSA and previous negative biopsies; men being evaluated before entering active surveillance; men being evaluated during active surveillance; and men with known, aggressive disease who are receiving the studies for staging or preoperative planning, Costa said.

"Except in the latter, targeted prostate biopsies became an important element in the evaluation of most of these patients," he told AuntMinnie.com. "As we look into the future, natural follow-up studies include evaluating the long-term impact on patient outcomes that is expected secondary to the improved diagnostic performance. This should provide important data to more objectively assess cost-effectiveness of this technology."