In an ideal world, after radical prostatectomy, the pathologist would send a favorable report to the surgeon: "I've looked at the prostate tissue you removed from your patient and all of the edges are clear. You've removed all the cancer."
Often, it happens that way. Sometimes, however, the pathologist's report is more ambiguous. Either the margins — the edges of the removed tumor — are positive, meaning they show the presence of cancer cells, or they're "close," meaning cancer is just a hair's breadth away from the edge of the specimen. Fortunately, studies show that close margins are not associated with a higher rate of recurrence.
A study looked at patients whose tumors were particularly close — less than two-tenths of a millimeter — from the surgical margin, the edge of the removed tissue. Even though there wasn't a comfortable cushion of tissue between the tumor and the edge of the prostate, patients did just as well as when there was more separation between the tumor and the margin.
And, even when the surgical margins are positive, cancer has not necessarily been left behind. While patients with positive surgical margins are more likely to have their cancer recur than patients with negative margins, many patients with positive surgical margins never have cancer recur. There are several possible reasons why the cancer may be cured even when the margins are positive. One is that it may take more than just a few cancer cells at the margin to grow a new tumor. For example, in studies in which cancer cells are injected into animals to study tumor growth, a minimum of 1,000 cells generally must be injected in order for cancer to develop in the animal. It's also possible that in some cases of positive surgical margins, the surgeon literally cuts across the last few tumor cells so that what appears to be remaining cancer is actually a cross-section of the perimeter tumor cells. Even though it looks like a positive margin, there's really nothing left.
Another possible explanation is that the act of surgery itself may kill any remaining cells. No cut or injury to tissue happens in a vacuum. The area around the cut is affected, too. (Think of lightning striking a tree. The tree dies, but so does a ring of grass around it.) When the surgeon cuts across tissue, the blood supply is cut off, killing the last few tumor cells that have been left behind.
There's also the potential that it's an "artifactual" (fake) positive margin. When the doctor, nurse and pathologist handle the removed tissue, they may inadvertently rub off a level of healthy tissue that would have indicated a positive margin.
In one study that evaluated positive surgical margins, a second surgery was done to remove more of the surrounding tissue. The first and second tissue specimens were examined. In 40 percent of cases where the first specimen appeared to show a positive surgical margin, the second specimen showed no sign of cancer.
A positive margin, or for that matter, a close margin, doesn't necessarily mean another form of therapy, like radiation, is needed. These studies suggest that patients may do just as well without additional treatment.
Your doctor will take into account the pathology report and other factors in determining whether further treatment is necessary. Even when some cancer cells remain after surgery, men often can be cured with radiation treatment to the prostate bed, the area where the prostate used to be.
