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| |  Advanced Imaging Can Aid Prostate Cancer Diagnosis, Treatment: Presented at ASCO-GU By Fred Gebhart SAN FRANCISCO -- March 8, 2010 -- Accurate diagnosis and staging is one of the persistent problems in treating prostate cancer. T stage, Gleason score, and prostate-specific antigen levels are all helpful, but they also create broad categories that include a wide pathologic and clinical range. Advanced imaging techniques can help clinicians localise the primary tumour, outline local extracapsular extensions, detect local and regional adenopathy, and identify distant bone metastases, researchers said here at the 2010 Genitourinary Cancers Symposium (ASCO-GU). “The portion of high risk prostate cancers is decreasing,” said Mukesh Harisinghani, MD, Massachusetts General Hospital, Boston, Massachusetts, here on March 5. “At the same time, high-risk patients tend to get treated less effectively. Advanced imaging techniques can help stage disease and plan treatment more effectively.” Most clinicians have access to conventional magnetic resonance imaging (MRI), Dr. Harisinghani explained, but more advanced functional techniques can add significantly more detail to conventional images. Magnetic resonance spectroscopy (MRS) measures relative concentrations of specific metabolites. A normal peripheral zone contains high levels of citrate and low levels of choline while prostate cancer shows the reverse, low levels of citrate and elevated levels of choline. A higher choline to citrate ratio suggests a more aggressive tumour. “The challenge here is that MRS requires some special technical expertise,” said Dr. Harisinghani. “The technology is not as prevalent as we would like.” Dynamic contrast-enhanced MRI is more readily available, he continued. Gadolinium contrast agents allow the operator to produce colour maps showing changes in vascularity and tissue permeability. Prostate cancer shows early rapid enhancement and early washout compared with normal prostate parenchyma. Diffusion-weighted MRI uses the differential diffusion of water in normal prostate tissue versus tumour tissue to localise tumour location. Diffusion is restricted in tumour tissues, which can be seen using current MRI equipment and standard operator expertise. Dr. Harisinghani noted that the most effective method to produce a detailed MRI of the prostate is to use an endorectal coil. Using a coil offers better spatial and contrast resolution than ultrasound or computed tomography and permits a more accurate delineation of prostate contours as well as the internal anatomy. A coil is particularly useful in high-risk patients because it allows better visualisation of any extracapsular extension and seminal vesicle involvement. Specificity is more important than sensitivity, he continued, and successful prostate imaging is highly dependent on operator expertise. Dr. Harisinghani also recommended the use of a higher energy 3 tesla scan if possible rather than the more traditional 1.5 tesla level. The higher energy scan offers a choice of a faster scan and conventional resolution or conventional scan speed and higher resolution. One of the most effective methods to identify bony metastases is 18-F fluoride positron emission tomography. Conventional bone scanning has high sensitivity but lacks specificity because benign bony conditions can appear as focal sites for metastases. 18-F fluoride is more specific because malignant lesions have a higher uptake than nonmalignant masses. “There is significant added value in imaging, particularly for higher risk patients,” Dr. Harisinghani said, “but we still have a ways to go in terms of access to the technologies and operator expertise.” The conference is sponsored by the American Society of Clinical Oncology (ASCO), the American Society for Therapeutic Radiation Oncology (ASTRO), and the Society of Urologic Oncology (SUO). [Presentation title: Usefulness of Imaging in High-Risk Prostate Cancer]
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