NEW YORK (Reuters Health) Aug 08 - Prostate cancer diagnosis tends to be delayed and complete surgical resection more difficult in obese men than in lean men, according to two reports in BJU International, published online on August 8.
The primary reason for the delay in diagnosis, and consequently poorer outcome, Dr. Stephen J. Freedland and colleagues suggest, is that "prostate-specific antigen (PSA)-based screening is biased against obese men," due to lower PSA levels caused by hemodilution from a larger plasma volume.
Dr. Freedland, at Duke University Medical Center in Durham, North Carolina, and his team tested this theory by comparing outcomes of radical prostatectomy for PSA-detected cancers and those identified by digital rectal exam (DRE). Their analysis included nearly 3400 men enrolled in the Shared Equal Access Regional Cancer Hospital (SEARCH) and Duke Prostate Center databases, treated between 1988 and 2007.
A higher BMI was significantly associated with high-grade disease, positive surgical margins, and biochemical progression, the team found.
However, the association between BMI and disease progression was limited to men treated since 2000, when PSA screening was the norm. Among obese patients with stage T1c disease treated since 2000, the risk of recurrence was more than doubled.
By contrast, obesity had no effect on the risk of progression for cancers detected by DRE. Thus, the research team recommends "lowering the PSA threshold for biopsy among obese men."
In the second report, Dr. Freedland's group studied the relationship between obesity and positive surgical margins after radical prostatectomy among 1434 men in the SEARCH database.
A higher BMI was associated with an increased incidence of positive surgical margins at all anatomical locations. Overall risk was 45% higher in mildly obese men and 128% higher in moderately and severely obese men relative to normal-weight men.
"Importantly," the authors note, "we did not detect a significant association between higher BMI and either extracapsular extension or seminal vesicle invasion, suggesting that the excess risk of positive surgical margins in obese men results from suboptimal technique rather than... advanced disease."
They explain that excess abdominal fat makes access to the prostate more complicated when resection is performed through a retropubic incision or by laparoscopy, whereas the larger prostate size in obese men makes removal more difficult through a perineal approach.
Among men with a BMI of 35 or higher, positive surgical margins occurred most frequently at the apex, leading the investigators to conclude that "although care should be taken in general when operating on obese men, perhaps additional care is needed in the apical area to prevent iatrogenic positive surgical margins."
Abstract and Introduction
Abstract
Epidemiologic studies of statin use in relation to prostate cancer risk have been inconclusive. Recent evidence, however, suggests that longer-term use may reduce risk of more advanced disease. The authors conducted a population-based study of 1,001 incident prostate cancer cases diagnosed in 2002-2005 and 942 age-matched controls from King County, Washington, to evaluate risk associated with statin use. Logistic regression was used to generate odds ratios for ever use, current use, and duration of use. No overall association was found between statin use and prostate cancer risk (odds ratio (OR) = 1.0, 95% confidence interval (CI): 0.8, 1.2 for current use; OR = 1.1, 95% CI: 0.7, 1.8 for >10 years' use), even for cases with more advanced disease. Risk related to statin use, however, was modified by body mass index (interaction p = 0.04). Obese men (BMI ≥ 30 kg/m2) who used statins had an increased risk (OR = 1.5, 95% CI: 1.0, 2.2) relative to obese nonusers, with a stronger association for longer-term use (OR = 1.8, 95% CI: 1.1, 3.0 for ≥ 5 years' use). Although statin use was not associated with overall prostate cancer risk, the finding of an increased risk associated with statin use among obese men, particularly use for extended durations, warrants further investigation.
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