"Our study is focused on a large group of men who have had a prostate biopsy that is benign but are still at a very high risk for prostate cancer," said Andrew Rundle, Dr.P.H., associate professor of epidemiology at Columbia University Mailman School of Public Health in New York, N.Y. "Studies conducted in the past have attempted to determine if there are subpopulations of men diagnosed with benign conditions that may be at a greater risk for developing prostate cancer. This is one of the first studies to assess the association between obesity and precancerous abnormalities."
Rundle and his colleagues investigated the association between obesity and future prostate cancer incidence within a cohort of 6,692 men at the Henry Ford Health System who were followed for 14 years after a biopsy or transurethral resection of the prostate with benign findings. The investigation was part of a larger study of environmentally-induced tissue biomarkers for prostate cancer funded through a research grant awarded by the National Institutes of Health to Benjamin Rybicki, Ph.D., a research scientist at the Henry Ford Health System and the senior co-author of the study.
The researchers conducted a case-control study among 494 of these patients and 494 matched controls; they found precancerous abnormalities in 11 percent of the patients' benign specimens. These abnormalities were significantly associated with obesity at the time of the procedure, according to Rundle.
After accounting for several variables, including family history of prostate cancer, prostate-specific antigen (PSA) levels during the initial procedure, and the number of PSA tests and digital rectal exams during follow-up, the researchers found that obesity at the time of the initial procedure was associated with a 57 percent increased incidence of prostate cancer during follow-up.
Rundle noted, however, that this association was only apparent for tumors occurring earlier in the follow-up period. "We don't absolutely know what the true biology is," said Rundle. "In some ways, this reflects the association between the body size and larger prostate size, which is thought to reduce the sensitivity of the needle biopsy. It is possible that the tumors missed by initial biopsy grew and were detected in a follow-up biopsy."
The association observed between body size and prostate cancer risk is larger than that seen in prior studies, according to Rundle. He attributed the differences to the variables of the cohort, which was composed of men at high risk for prostate cancer. In addition, since these high-risk men were members of the Henry Ford Medical System, they underwent increased medical surveillance, which included repeated biopsy and regular PSA screening.
"We need some guidance on when or for whom a full follow-up is required," said Rundle. "Obesity should be considered a factor for more intensive follow-up after a benign prostate biopsy."