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The Prostate Lab

"Focused on the Prostate since 1996"

DNA Ploidy 101 -A simple explanation (local link)

DNA Ploidy Analysis

[Written and Researched May 1996,]

By JR Oppenheimer, M.D., F.C.A.P.

Prostate pathologist on line

Both flow cytometry and and static image analysis have been used to determine DNA content (ploidy) of prostate cancer (CaP). DNA studies have shown that, as a group, patients with diploid cancers have longer disease free intervals and survival times than those with non-diploid tumors (Zinke, 1997). However, they may not be so helpful in predicting stage for an individual patient.

Because diploid tumors are more responsive to hormonal therapy (Zinke, 1992,1997), the Prostate Cancer Working Group (sponsored by the College of American Pathologists) has found that DNA ploidy studies are useful in patients with T3 or node-positive disease. As of June 1995, the Working Group does not recommend DNA analysis in T1, T2, or node-negative disease because of conflicting results in the literature (Grignon 1995). It still might be useful to have this data in case consensus is eventually reached, however.

Studies demonstrating the utility of DNA ploidy status have been performed on whole prostates obtained after RP. Since CaP is often a heterogeneous and multifocal disease, it doesn't necessarily follow that a tiny piece of tissue obtained on needle biopsy is representative of the lesion as a whole. Two reports have confirmed that ploidy status differs in different parts of an involved prostate (Greene,1991;O'Malley,1993). This intratumor variation in DNA ploidy suggests that multiple site sampling (possibly by fine needle aspiration) may be necessary to obtain accurate DNA measurements. Thus it may be misleading to assume that a tumor is entirely diploid when only a small fraction of it is sampled. Nevertheless, three studies have shown correlation between ploidy on needle biopsy and subsequent RP material (Leung,1994; Takai1994, Ross 1994).

The lack of mutually accepted standards limits the usefulness of ploidy analysis.

Both flow cytometry and image analysis techniques suffer from limitations.

Should DNA ploidy be determined from needle biopsy or RP tissue in order to determine prognosis?

In conclusion, it appears premature to place too much emphasis on DNA ploidy analysis performed on needle biopsy cores


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