Obesity was associated with an increased risk of precursor lesions among men with an initial benign prostate biopsy result, according to a nested study of nearly 500 prostate cancer cases and matched cancer-free controls.
Further, obese men also were more likely to have benign findings on initial core needle biopsy or transurethral resection of the prostate (TURP) and to then go on to develop prostate cancer within 4 years after their procedure.
Dr. Andrew Rundle
"This is one of the first studies to assess associations between obesity and PIN (prostatic intraepithelial neoplasia)," reported Dr. Andrew Rundle of Columbia University, New York, and colleagues. The research was published in the April 23 online issue of Cancer Epidemiology, Biomarkers & Prevention (doi: 10.1158/1055-9965.EPI-12-0965). With approximately 1 million prostate biopsies conducted annually in the United States – two-thirds of which return negative results – obesity may be a factor to consider in the follow-up of individuals after an initial benign procedure.
In the study, obese men were more than twice as likely to have PIN detected in their initial benign specimens (OR = 2.17; 95% CI 1.13–4.15).
After adjustment for factors such as family history and prostate-specific antigen (PSA) levels, obesity at the time of the initial procedure was also associated with a significant increase in the incidence of prostate cancer, but only within 1,538 days of the initial procedure, which was the median duration of follow-up (OR = 1.95; 95% CI, 1.09-3.48).
Overall, a higher PSA value at the initial procedure and a family history of prostate cancer were associated with prostate cancer incidence, as was the number of PSA tests performed during follow-up. The association between obesity and prostate cancer incidence was confined to diagnoses occurring within less than 1,538 days, which was the median duration of follow-up after the initial benign procedure.
The findings emerged from a study that recruited 494 prostate cancer cases and matched cancer-free controls from a historical cohort of nearly 6,700 men followed up after a needle core biopsy or TURP. All had a benign prostate specimen collected between January 1990 and December 2002 and were followed up to December 2007 at the Henry Ford Health System in Detroit. The incidence of prostate cancer within this high-risk cohort was approximately twice that of the general Detroit Surveillance Epidemiology and End Results (SEER) population, although the ratio of African American to white cases in the cohort was similar to that in the overall SEER data.
All subjects had a recorded PSA level within a year of their initial benign procedure cohort entry and no history of a previous prostate cancer diagnosis. Patients diagnosed with prostate cancer less than 1 year from the date of their initial benign procedure were ineligible for the study. Controls were randomly selected from among those cohort members who were free of prostate cancer at a follow-up duration greater than or equal to the time between cohort entry and diagnosis of the matched case.
Body mass index was calculated from medical record data on height and weight measured within 115 days of the benign procedure. Overweight was a BMI of more than 25 and less than 30 and obese was a BMI of 30 or more. Surgical specimens were reviewed for the presence of PIN by a single urological pathologist who was blinded to prostate cancer outcomes at the time of review. Advanced stage disease was defined as pathologic or clinical stage T3a and higher.
In this study, in contrast to earlier cohort studies, obesity was not associated with high Gleason grade tumors, and obesity seemed to be more likely to be associated with low-grade tumors. "If the missed tumors were small and low grade, then they may have still been of lower grade when diagnosed in the first few years after the initial biopsy with high-grade prostate cancer and unassociated with or perhaps even protective for localized or low-grade disease," the researchers reported.
Obesity has been thought to reduce the sensitivity of PSA testing and, thus, may delay referral for biopsy. Obesity may also reduce the diagnostic efficiency of needle biopsies, as obese men have larger prostates and small tumors may be more likely to go undetected until they grow and are detected in subsequent biopsies during follow-up, the authors wrote.
The study was supported by a grant from the National Institute of Environmental Health Sciences, and the authors did not declare any potential conflicts of interest.