PIN and Prostate Cancer:
New Studies Show Less Risk
by William J. Catalon, MD
PIN (prostatic intraepithelial neoplasia), a microscopic finding reported in 5% to 10% of prostate biopsies, has been regarded as a red flag suggesting the possible presence of cancer.
However, in recent years, some research groups have found that men who have had very thorough first biopsies had a substantially lower incidence of cancer following an initial biopsy showing PIN.
The prostate contains innumerable tiny spherical glands that drain into the urethra through their duct. These spheres have a wall two-cell layers thick and are covered on the outside by a membrane called the basement membrane.
Prostate cancer usually arises on the inside of these spherical glands, and when the cancer cells break through the basement membrane into the surrounding tissue, it is considered a full-fledged invasive prostate cancer.
"To avoid need for repeat biopsies, more biopsy cores should be taken at first session."
PIN is the finding of malignant-looking cells on the inside of the spherical glands that have not broken out through the basement membrane.
Traditionally, PIN has been considered to be a pre-cancerous condition and/or a satellite "tumor" in the neighborhood of an invasive prostate cancer.
In 1995, my research group reported from our PSA Study that 51% of men with high-grade PIN were subsequently diagnosed with prostate cancer within a few years.
Other researchers reported similar findings, and it became standard procedure to recommend repeat biopsies within 6 months in men with high-grade PIN.
At the 2003 American Urological Association Meeting, my research group, including Dr. Neriman Gokden, Dr. Peter Humphrey and Kimberly Roehl reported on an update in this area from our PSA Study.
We evaluated men who did or did not have PIN on their initial biopsy. Men in both groups subsequently underwent a repeat biopsy if they had a persistently elevated PSA level.
The risk for prostate cancer in men with PIN on their initial biopsy was much lower than the 51% earlier reported. In fact, the findings were surprising: 28% with PIN subsequently had cancer detected.
"...Likely in past that cancers were missed in initial biopsy and only the PIN was detected."
The incidence of subsequent cancer diagnosis had decreased from 51% to 28% in the patients with PIN.
A possible explanation for this decline in overall risk of cancer following the finding of PIN is that more biopsy cores are currently obtained from patients than were performed in the past. Therefore, in the past, it is likely that many cancers were missed by the initial biopsies and only the associated PIN was detected.
Then, when the repeat biopsies were taken and more adequate sampling of the prostate gland was achieved, the missed cancers were discovered. However, now that more biopsy cores are taken initially, fewer of the cancers are missed initially, and so the percentage with cancer on followup biopsies for PIN is lower.
This study provides patients and doctors with a more accurate risk assessment on the need for repeat biopsies after finding PIN on an initital biopsy. To avoid the need for repeat biopsies, patients and doctors should insist on having more biopsy cores taken (at least 8 cores) during the first biopsy session.
If PIN is found, the biopsies should still be repeated (in 3 months); however, the risk of discovering cancer is lower than previously believed.
Each time a biopsy session shows no cancer, the patient has a degree of confidence that if a dangerous cancer were present, it should have been discovered.
However, with time, if the PSA continues to rise, and does not come down with antibiotic therapy, further repeat biopsies are indicated.