Positive Margins after Surgery for Prostate Cancer: Part One

The anatomical location of the prostate gland, situated within millimeters of the bladder and rectum, means that urologists are simply unable to cut a wide margin around the gland.  Slicing into the bladder or rectum is not an option. Unfortunately, if a patient’s cancer grows through the capsule, rather than cutting around the cancer, the surgeon will be forced to cut through the cancer during the attempt to remove the gland.

When this occurs it is called a “positive margin.”

Leaving cancer behind is certainly a dismal failure.  After all, if the cancer can’t be completely removed, why do the operation?  The reality is that prior to the operation there is always uncertainty about the extent of the cancer.  During the operation, microscopic disease that is outside the prostate is invisible to the naked eye.  Remember, the art of surgical prostate removal was developed in a previous era when all cancers were perceived as life-threatening and surgery was the only option available. Back then, radiation technology was decidedly inferior. Cure rates were much lower with radiation and toxic side effects were worse.

Modern imaging with 3T multi-parametric MRI performed prior to surgery, while not perfect, has the potential to enhance surgical planning greatly.  Unfortunately, only a minority of the 70,000 men undergoing surgery every year benefit by having a scan for surgical planning prior to doing an operation.

Hopefully, this policy will change.

Due to the anatomical circumstances outlined above, cancer on average is left behind in the patient’s body anywhere from 10-50% of the time. A positive margin first comes to the patient’s attention a few days after the operation. After removal, the prostate is analyzed in the laboratory by a specialized physician called a pathologist.

The prostate is prepared for microscopic evaluation first by dropping it into a bottle of ink so that the whole outer layer of the gland is covered.  Then the gland is sliced horizontally into thin areas with special attention be paid to the area of the gland where the cancer is located. The pathologist pays particular attention to the edge of the gland by perusing it under a microscope.  If tumor is observed “butting up” against an inked area, that means the surgeon’s scalpel cut through tumor during the operation, leaving tumor behind in the patient’s body.  

The presence of a positive margin can be more or less serious depending on the Gleason score and the extent of the positive margins.  Across the board, the average risk of future cancer relapse in men with positive margins is about 50%. However, when the Gleason score is higher or if the positive margins are extensive, the risk of future relapse may approach 100%. 

Deciding on further treatment after surgery when margins are positive can be challenging.

One option is to simply observe the situation while monitoring PSA levels closely.  This approach is more attractive when the Gleason score is lower and less extensive positive margins are present. The men who remain in remission can avoid the treatment-related side effects from radiation altogether.  Also, in this era of rapidly advancing technology, men who undergo delayed treatment for a rising PSA years down the road may grandfather into an era of improved therapy that is less toxic and more effective.

For men who decide to pursue observation, PSA monitoring should be performed with ultrasensitive technology. Then, if the PSA rises, treatment can be initiated at a very early stage, when the PSA is still less than 0.1.  Cure rates are certainly best when treatment is started at a lower level of PSA. The management of men who have more extensive margins are addressed in Part Two of this article.

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