Biopsy May Underestimate Prostate Cancer Grade in Obese Men

DURHAM, N.C., March 28 -- Biopsies may underestimate the severity of prostate cancer in obese men, a team of investigators found.

In a study comparing biopsy results and surgical specimens in more than 1,100 men who underwent radical prostatectomy, obese men were significantly more likely than men of normal weight to have cancers that turned out to be of higher grade, reported Stephen Freedland, M.D., of Duke, and colleagues, in the March issue of Urology.

"We already know that it's more difficult to diagnose prostate cancer in obese men because they have lower levels of prostate-specific antigen?and because their larger-sized prostates make it more likely for a biopsy to miss the cancer," said Dr. Freedland, "These findings further suggest that we could be missing even more high-grade disease among obese men."

He and his colleagues used the Shared Equal Access Regional Cancer Hospital (SEARCH) database, a large-scale, multicenter, multiethnic repository of information on men at the Veterans Affairs Medical Centers in Los Angeles, Palo Alto and San Francisco, in California, and in Augusta, Ga., and at the San Diego Naval Hospital.

Seeking possible factors that could predict the risk that the cancer detected on biopsy would be upgraded or downgraded on histologic and pathologic examination after surgery, the investigators looked at a sample of 1,113 men who underwent radical prostatectomy from 1996, when extended biopsies became the regular protocol, to 2005. To be included in study, the men had to have undergone biopsy with a minimum of six cores.

The authors grouped the patients into three categories according to the sums of Gleason scores: 2 to 6, 3 + 4 = 7, and 4 + 3 or greater.

They found that 299 men (27%) had biopsy findings that after prostatectomy were upgraded, while 123 (11%) had results downgraded. For the remaining 691 men (62%) the post-biopsy and post-prostatectomy Gleason sums jibed precisely.

Upgrading was associated with adverse pathologic features (P

"If we can determine through additional biopsies that an obese or overweight man has more aggressive prostate cancer, we can discuss whether the cancer should be treated with more than one approach, such as combining hormonal therapy with radiation, to reduce the risk of the cancer spreading and improve the chances of cure," Dr. Freedland said.

"We must also keep in mind that even if a well-done biopsy shows low-grade cancer in an obese patient, there is still a reasonable likelihood that the patient may have high-grade disease."

The authors noted as a possible limitation of their study the fact that they did not use centralized pathologic evaluation of the surgical specimens, but pointed out that both biopsy samples and surgical specimens were examined by the same pathologists at each center, and that they used a rigorous protocol for processing radical prostatectomy specimens.