This is the fourth article in a series of stories about new technology for cancer diagnosis or treatment. View a list of articles in this series.
Testing a “Smarter” Biopsy for Prostate Cancer
The patient, a 63-year-old African American, had undergone 10 separate biopsies for prostate cancer over the previous decade, and each test had come back negative for cancer. Based on the patient’s history of a rising prostate-specific antigen (PSA) level, his urologist suspected cancer but could not find it. Finally, last spring, the urologist referred his patient to Dr. Peter Pinto of NCI’s Center for Cancer Research (CCR) to enroll in a clinical trial testing an experimental image-guided biopsy.
Using the new approach, Dr. Pinto and his colleagues identified six lesions in the patient’s prostate that all tested positive for cancer. The lesions were in the anterior prostate, a region that is difficult to assess by conventional biopsy or digital rectal exam. But the lesions showed up on magnetic resonance imaging (MRI) scans, and Dr. Pinto used the image-guided system to collect tissue from the precise locations in the prostate.
“When the patient came to see us, there was considerable frustration on the part of the urologist, who had been repeating the same biopsy technique over and over expecting a different result,” recalled Dr. Pinto, a member of CCR’s Urologic Oncology Branch. “But there really were not any other options until the image-guided approach became available.”
After learning the biopsy results, the patient decided to have his prostate removed surgically, and Dr. Pinto performed the operation at the NIH Clinical Center.
Fusing MRI and Ultrasound Images
Developed by a multidisciplinary team that includes clinicians, researchers, engineers, and computer scientists, the image-guided biopsy represents a kind of global positioning device. A patient’s initial MRI serves as a template for directing needles to specific places in the prostate and mapping the locations of suspected cancer. Prior to the biopsy, the MRI data are merged, or fused, with real-time ultrasound imaging data, and together these data guide the procedure.
“This technology gives you a smarter, truer biopsy,” said Dr. Bradford Wood, who directs the NIH Center for Interventional Oncology and is leading the research with Drs. Pinto and Peter Choyke of CCR. “All too often the standard biopsy is inadequate. A suspicious area may be hidden from the standard technique, and this approach offers another way of mapping the tissue.”
With a conventional prostate biopsy, 6 to 12 needles are inserted into selected regions of the gland. (The sites of these insertions are not recorded.) This approach is not comprehensive and may miss cancer. What’s more, a needle that hits cancer may not strike the center of a lesion, which could lead doctors to underestimate the stage of a patient’s disease.
You must have flash installed and enabled to view the video.
“Patients in this trial recognize that the needle biopsy gives an incomplete picture of what’s going on in prostate cancer,” said Dr. Choyke, chief of NCI’s Molecular Imaging Program. “They are happy to come in for an MRI because they want to have a better picture of their disease.”
Dr. Pinto added: “It seems to me that prostate cancer is the only solid tumor that doctors find by randomly sampling an organ.”
The image-guided system adds about 5 to 7 minutes to a conventional prostate biopsy, said Dr. Baris Turkbey, a radiology fellow in CCR, who has overseen the MRI scans for many of the nearly 260 men in the trial. Although the technique is still experimental, the NIH researchers are working with their partners at Philips Healthcare to transform the research platform into a commercial tool that could be used by urologists on an outpatient basis.
In a recent study, the researchers described the technology and reported results for 50 patients. The system, they concluded, may be useful for documenting the location of prior biopsies as well as directing subsequent biopsies to regions of the prostate not previously sampled. Because the needles are equipped with tracking devices, the precise locations of each sample could be recorded for patients undergoing active surveillance (formerly known as watchful waiting).
Toward Targeted Treatments
In addition to finding cancers, the system could also lead to more targeted treatments for the disease. “This platform may play a role in allowing us, one day, to offer patients focal therapy for prostate cancer,” said Dr. Pinto. Focal therapy involves techniques such as freezing or burning lesions within the prostate gland while sparing healthy tissue.
The techniques for freezing and burning lesions in the prostate exist now, Dr. Choyke noted. “But the critical question for the field has been: how do you identify the targets?”
Another challenge for researchers is finding ways to distinguish lethal prostate cancers from those that may never cause harm in a man’s lifetime. Current treatments for prostate cancer—including prostatectomy, radiation, and ablation—target the entire prostate gland, and all have potential side effects such as incontinence, rectal injury, and loss of sexual function.
Along with the image-guided biopsy, the researchers are also testing molecular imaging agents that could provide information about the biology of the cancer rather than just the location. (See video above.) The two approaches are complementary and could lead to ways to distinguish the lethal and nonlethal forms of the disease, the researchers said.
A goal of the current work, said Dr. Wood, is to “narrow the gap between diagnosis and treatment.” Instead of merely diagnosing a patient’s cancer, the researchers want to be able to use the information they collect at diagnosis during treatment. Toward that end, the imaging system could be modified to target lesions in the prostate, and clinical trials are being designed using focal prostate therapy, he noted.
In the current trial, after Dr. Pinto surgically removes a patient’s prostate, it is placed in a specially designed mold and sent to NCI’s Laboratory of Pathology. There, Dr. Maria Merino examines the specimen according to the same “cut lines” that were used on the imaging studies to confirm that suspicious lesions on an MRI really are cancerous. This process could eventually reveal associations between lesions found on MRI and certain types of disease.
In the meantime, participants in the trial are helping to advance the research. As one patient told Dr. Pinto, “My father had prostate cancer, and I have prostate cancer. By participating in this study, I know that my son may have better care if he gets the disease.”
—Edward R. Winstead