The Wednesday news update: January 28, 2009

Reports summarized today include one on the potential of “dynamic contrast-enhanced” magnetic resonance imaging (DCE-MRI) and a second on the impact of obesity on risk for prostate cancer detection.

Jackson et al. have reported on the potential of dynamic contrast-enhanced MRI (DCE-MRI) as a method for tumor visualization that may be superior to either CT scanning or standard MRI imaging. Specifically, they discuss a study in which 18 patients with prostate cancer had T2-weighted MRI and DCE-MRI prior to prostatectomy. The prostate was sectioned meticulously post-surgery so as to achieve accurate correlation between imaging and pathology. The location of tumor on imaging was compared with histology, and the accuracy of DCE-MRI and T2-weighted images was then compared. Interpretation of DCE-MRI and T2-weighted images by a radiologist showed DCE-MRI to be more sensitive than T2-weighted images for tumor localization (50 vs 21 percent; p = 0.006) and comparably specific (85 vs 81 percent; p = 0.593). The authors conclude that the superior sensitivity of DCE-MRI compared with T2-weighted images, together with its high specificity, is arguably sufficient for its use in guiding radiotherapy boosts in prostate cancer. The unanswered question, of course, is whether DCE-MRI is comparable to the T3-weighted MRI imaging that is now available at several centers in the USA.

Pruthi et al. have reported on a modern, single-institution series of 500 men in an attempt to clarify whether there is any association between obesity and risk for detection of prostate cancer. In this study, a series of men with an increased or increasing PSA or abnormal DRE underwent transrectal ultrasound-guided biopsy of the prostate. All men had an extended 10- to 12-core biopsy and were categorized according to body mass index (BMI)  into one of juat two groups: non-obese (<30  kg/m2) and obese (>30 kg/m2). (Other studies have commonly separated the non-obese category into normal and overweight  groups, based on BMIs of < 25 and 25-30 kg/m2, respectively). Of the participants, 26 percent were considered obese and 45 percent had prostate cancer based on their on biopsy results, but there was no difference in mean BMI between those with a positive vs. a negative biopsy. Obese men were younger, had larger prostates, and were less likely to have an abnormality on DRE. The investigators did a subset analysis on 367 men with a PSA level < 10 ng/ml and again found no differences in the biopsy rates of obese vs. non-obese men.While previous studies have demonstrated a higher rate of detection of prostate cancer in obese patients by using an extended prostate biopsy scheme, this study did not find that obese men had a higher rate of prostate cancer detection.

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