Seeing what can’t be imaged
Improved imaging systems are also helping Yale physicians treat cancers specific to men. Prostate cancer is even harder to find than cancer of the breast, because the prostate is the only solid organ in which cancer cannot be imaged. Ultrasound—the modality that guides clinicians to the prostate—alone cannot see tumors, says Peter Schulam, M.D., director of the Cancer Center’s Prostate and Urologic Cancer Program. His team, like those of other specialists, uses a combination of imaging modalities that work better together than separately.
When Schulam arrived at Yale from UCLA last year, he recruited a team of doctors, engineers, and radiologists. He also brought a 3-D imaging navigation system called the Artemis Device, which he says is the best available to identify and monitor the progress of prostate cancer.
“Every man with prostate cancer doesn’t need to be treated,” Schulam says. “The question is: How do you differentiate?” Prostate cancer kills roughly 30,000 American men every year—more than any other malignancy except lung cancer, according to the American Cancer Society. Most men diagnosed with the disease, however, die of some other cause.
High levels of prostate-specific antigen (PSA) may signal cancer, but an enlarged but healthy prostate can also raise PSA levels. In 2012, the USPSTF recommended against PSA screening for cancer, saying that men are too often treated when the disease isn’t causing symptoms. CT scans aren’t beneficial in detecting possible cancer, so doctors increasingly use MRI. “The problem is that once you see something suspicious on an MRI, it’s hard to biopsy” because the powerful magnets prevent the use of needles, Schulam says. A prostate biopsy is often educated guesswork, with doctors taking a dozen or so passes with a 1-millimeter-thick needle into the walnut-sized gland. Not only are biopsies often painful procedures and recovery can lead to such complications as sepsis, but “you can miss cancer,” Schulam says. “Or you can detect cancer but not know the volume of cancer.”
Because prostate cancer generally progresses very slowly, treatment options range from radiation or removal of the prostate to watchful waiting, in which doctors take no significant action unless the diseased organ causes problems. Active surveillance—careful monitoring for signs that the disease is progressing—is a relatively recent approach that falls somewhere in between. It is usually recommended for men at low risk of developing symptoms from the disease. Artemis, which combines MR and ultrasound images to improve the detection and treatment of prostate cancer, is the key tool in the image-guided approach to active surveillance of the disease.
Artemis uses a multiparametric MRI—which also measures chemical concentrations and blood flow in tissue—to identify regions of the gland that may be cancerous. “The machine takes the MRI image and an ultrasound image and puts them together in a 3-D model,” says Preston Sprenkle, M.D., a urologist on Schulam’s team. The real-time ultrasound feature then “helps us guide where our needles go,” so biopsies aren’t as blind as they have been in the past.
The team can then determine how diseased the prostate is through what’s called a Gleason score—which predicts whether the cancer will grow and spread to other organs—and what action comes next. Men with a low Gleason score can prevent or postpone unnecessary radiation therapy or a prostatectomy, which can leave patients incontinent or impotent. “If you lose one or both of those, your quality of life is dramatically changed,” Sprenkle says.
Artemis promotes active surveillance because it “records exactly where the biopsy was taken from,” Schulam says. When the team members examine the gland a second time, they have a superimposed image so “we can biopsy the exact same place as before. If something changes, you intervene such that you haven’t lost your window of opportunity to achieve cure.”
To see more, visit https://medicine.yale.edu/publications/yalemedicine/winter2014/features/feature/176993