• FRONTLINE CANCER:
Prostate cancer is the most common cancer in American men after skin cancer, with roughly 221,000 new cases each year. But while this number is high, the prognosis is pretty good: Virtually all men diagnosed with prostate cancer will survive five years or more if the disease is detected early enough.
Much of the credit for the low death rate goes to prostate-specific antigen (PSA) testing, which measures the level of a specific protein in the blood. PSA levels naturally rise with age, but higher levels can indicate the presence of cancer. In the 1980s, before the FDA approved PSA testing, the five-year survival rate for prostate cancer was 70 to 75 percent; now it’s 99 percent — a remarkable achievement.
A lot of things influence PSA level, many of them benign. There is no specific normal or abnormal level; much depends upon individual factors such as age and family history. Most men with an elevated PSA do not have prostate cancer, however, elevated PSA levels increase the chance of prostate cancer. Therefore, a high PSA level may prompt another PSA test to confirm, a physical exam and, perhaps, a prostate biopsy.
Prostate biopsies involve collecting multiple samples of prostate tissue using hollow needles inserted into the walnut-sized gland located just below the urinary bladder. The tissue is then microscopically examined for the presence of cancerous cells. The biopsy is typically directed by a transrectal ultrasound, performed under local anesthesia and takes about 10-15 minutes. There are some risks, which include pain, bleeding and, rarely, serious infections.
If a biopsy is deemed necessary, it obviously should be as efficacious as possible. Moores Cancer Center oncologists have significantly improved that prospect with the local debut of a new approach that melds ultrasound with magnetic resonance imaging (MRI) to create a three-dimensional map of the prostate, allowing physicians to view growths previously undetectable. As a result, biopsy needles can be more accurately targeted to sample places where cancer cells are believed to reside, resulting in fewer false-positives and earlier diagnoses.
The technique is being pioneered here by Christopher Kane, M.D., chair of the Department of Urology in the UC San Diego School of Medicine, and colleagues Karim Kader, M.D., Ph.D., and J. Kellogg Parsons, M.D., M.H.S. in collaboration with Department of Radiology colleagues.
Moores researchers are also advancing another new imaging technique that improves upon current prostate imaging — and may have significant implications for how patients with prostate cancer are ultimately treated.
The current standard of care for prostate imaging is an MRI using an intravenous contrast agent to highlight blood flow. Prostate MRIs is currently the standard of care for imaging patients with prior negative biopsies, but a continuing concern and for following men with low-aggression cancer to ensure a more aggressive cancer hasn’t been missed. Growing cancer cells typically require greater blood flow than surrounding healthy tissues so it’s hoped an MRI will note any differences that reveal the shape and nature of any tumor present.
But many tumors do not differ significantly from surrounding tissues, making it easier to avoid MRI detection. An imaging technique, described by a team of UCSD researchers in papers published earlier this year, builds upon an approach used to characterize brain tumors. Called restriction spectrum imaging-MRI (RSI-MRI), it measures diffusion of water in prostate tissues. The technique was co-developed by UCSD radiology faculty members Anders Dale, Ph.D., and Nathan White, Ph.D., and translated into clinical practice for the detection of prostate cancer by David Karow, M.D., Ph.D.
Cancer tissues are denser than healthy tissues and typically limit the amount and mobility of water within and around them. RSI-MRI, which corrects for magnetic field distortions found in ordinary diffusion MRIs, more accurately plots a tumor’s location and provides a more precise delineation of its extent. The latter is particularly important because it helps physicians better determine the course of treatment.
RSI-MRI is also quantitative and correlates with the Gleason tumor grade, a system that assesses the stage of a tumor and helps guide therapy. A lower RSI signal may suggest an indolent tumor that can be actively monitored rather than aggressively treated. A higher RSI signal may indicate aggressive disease that can be treated curatively with surgery or radiation therapy. This latest advance brings medicine a little closer to being able to predict tumor aggressiveness — and thus treatment — without resorting to invasive procedures or unnecessary or overly aggressive treatment.
RSI-MRI is now used clinically on all prostate MRI exams at UCSD Health — the only local health system to offer it. “RSI is very new, in the last one-and-a-half years for prostate,” said Karow, who leads the prostate imaging program. “RSI-MRI improves tumor visualization and is predictive of tumor grade and will likely expand to other institutions across the U.S. in the next few years. “
Under the direction of Drs. Kane, Parsons, Karow and their extraordinarily talented colleagues, prostate cancer has long been a major research interest at Moores, with studies in recent years looking at links to diet, statins (men taking the cholesterol-lowering drug may be less likely to experience prostate cancer recurrence after treatment), new chemotherapies and immunotherapies, and how to keep prostate cancer from metastasizing to bone, which dramatically worsens a patient’s prospects.
— Scott M. Lippman, M.D., is director of UC San Diego Moores Cancer Center. His column on medical advances from the front lines of cancer research and care appears in the La Jolla Light the fourth Thursday of each month. You can reach Dr. Lippman at firstname.lastname@example.org