Prostate cancer is the second most commonly diagnosed abdominal cancer in men and the second leading cause of cancer death in American men.
SCREENING OF PROSTATE CANCER
Currently, most clinicians rely strictly on clinical and laboratory parameters to guide decision making. Prostate cancer screening usually begins with a digital rectal exam (DRE) by a primary care physician or Urologist with a periodic evaluation of a patient's blood sample for prostate-specific antigen (PSA), a blood protein secreted by prostate cancer. In case of a palpable prostate nodule or elevated PSA, an ultrasound guided biopsy of the peripheral portion of the prostate is performed. The pathologist evaluates these samples under the microscope and decides whether the features of the prostate glands suggest the presence of cancer. If present, the cancer severity is graded using the Gleason Score.
TREATMENT OF PROSTATE CANCER
Treatment is then determined primarily by whether the disease is localized or metastatic. Localized cancer is treated by surgery (radical retropubic prostatectomy or RRP), external beam or proton beam radiation therapy, implanted seed radiation, or watchful waiting. Metastatic prostate cancer is treated with androgen ablation (hormone) therapy.
Thus accurate staging of prostate cancer is important to choose an appropriate therapy. Currently, probability tables (nomograms) are used in clinical practice to determine whether prostate cancer is localized to the prostate or has extended beyond the gland (staging).
MR imaging has been shown to improve accuracy of staging of prostate cancer in patients with intermediate or high probability of spread outside the gland.
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FIGURE 1: Prostate MRI: Diffusion & Spectroscopy
A: T2 Anatomic image
B: Applied diffusion coefficient
(tumor appears dark)
C: Abnormal spectroscopy
D: Normal spectroscopy
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FIGURE 2: Color Map of Choline: Citrate Ratio in a different patient
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Patients with localized cancer who are otherwise relatively healthy are given options of surgical removal of the prostate or treatment with one or more forms of radiation therapy. An increasing percentage of patients who choose surgery are choosing newer and less invasive surgical techniques such as laparoscopic or robotic assisted prostatectomy. However, in these techniques, the small incisions limit the surgeon's sense of touch in evaluating the different portions of the prostate gland during surgery compared with traditional open prostatectomy. Minimally invasive and robotic surgeons are increasingly turning to
preoperative MR imaging, to
help provide a roadmap to guide resection of cancer while preserving essential delicate arteries and nerves that help control urinary continence and sexual function.
At UCLA prostate magnetic resonance imaging (MRI) is supplemented by a variety of related functional MR techniques such as the technically demanding technique of magnetic resonance spectroscopic imaging (MRSI).
MRSI is a MR technique that enables detection and quantification of normal and cancer related chemical compounds in the human prostate gland (
fig. 1 & 2). Although normal human prostate contains large quantities of citrate and low levels of choline, prostatic adenocarcinoma contains lower levels of citrate and high levels of choline. The first successful demonstration of 1H MR Spectroscopy in distinguishing a variety of chemicals such as citrate, choline, spermine and creatine in human prostate was demonstrated by Dr Albert Thomas and colleagues in 1990. (JMR 1990). Since then, a variety of techiniques have been successfully implemented to determine the relative concentration of these chemicals.
NEW TECHNIQUES TO BETTER DETECT & STAGE PROSTATE CANCER
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FIGURE 3: Perfusion Map
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In addition to MRI and MRSI, newer techniques such as
MR diffusion and
MR perfusion imaging are being routinely used to better detect and stage prostate cancer to assist surgeons in planning minimally invasive surgery. Diffusion imaging is a much faster technique which, although still not as finely detailed as conventional MRI, provides information on the degree of cellular crowding, which is worse where cancer cells are rapidly turning over. Perfusion imaging has nearly the same fine detail as normal MRI, but provides a map of blood flow, which is increased in cancer cells. This last technique is just now exiting the realm of experimental use and is being gingerly applied to patient diagnosis and treatment planning (
fig.3).
These advanced preopreative imaging techniques enabled surgeons to more accurated decided when to remove or spare the delicate neurovascular bundles in different cases. These decisions do significantly affect patients' quality of life after surgery since urinary continence and sexual potency may be affected.
In some cases, a blood test may suggest cancer but the biopsies fail to localize it, and the surgeon may not be able to feel the cancer with the DRE. In these cases UCLA can provide magnetic resonance imaging with these new and established techniques to help find cancer and guide future biopsies.
NEW TECHNIQUE TO TREAT PROSTATE CANCER
In the near future, UCLA will be one of the few sites in the world to use MRI to guide focused high-energy sound waves to destroy prostate cancer without needles or surgery. This experimental technique, called
high-intensity focused ultrasound (HIFU) or
magnetic resonance-guided focused ultrasound (MRgFUS) uses the MRI to find all of the cancer inside the prostate gland, and then guides sound waves like a magnifying glass focusing the light of the sun to selectively "burn" the cancer cells but leaving healthy tissue, including the nearby arteries and nerves, untouched.
The radiologists, scientists and technologists at UCLA are working hard to bring cutting-edge science into clinical practice. We strive to help the urologists and cancer specialists of UCLA and the surrounding communities provide the most accurate and comprehensive treatment of prostate cancer available.
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