In the latest Case Record of the Massachusetts General Hospital, a 67-year-old man was seen in the cancer center of the hospital because of elevated prostate-specific antigen for 6 years. One of six transrectal prostate-biopsy specimens showed a tiny focus of well-differentiated adenocarcinoma. A diagnostic procedure was performed.
At least 30% of clinically important prostate cancers may be missed during transrectal ultrasound-guided biopsy, and the results are not improved if more than 12 cores are taken (so-called “saturation biopsies”).
• What is a Gleason score?
The Gleason score is the sum of the two most common histologic grades in a prostate-gland tumor, each of which is rated on a scale of 1 to 5, with 5 being the most cytologically aggressive. It correlates with prognosis. A higher score is more likely to be seen with disease that is not confined to the prostate, and is also correlated with poorer response to treatment of localized disease.
• What are the criteria for active surveillance in prostate cancer?
The authors report that criteria for active surveillance for prostate cancer include a PSA level less than 10 ng per milliliter. While the decision to carry out active surveillance is one that must be individualized, in general, in addition to having a relatively low PSA, patients with early clinical disease stage and a Gleason score indicating well or moderately differentiated tumor may be considered for active surveillance.
Morning Report Questions
Q: What is transperineal template-guided mapping biopsy (TTMB) of the prostate?
A: Traditional transrectal ultrasound-guided needle biopsy of the prostate allows excellent and convenient sampling of the posterior aspect of the prostate gland, where prostate cancers most commonly originate. On occasion, however, the cancer may arise either centrally or anteriorly and may be beyond the reach of a biopsy needle inserted through the rectum. However, the anterior gland can be reached through a perineal approach, a technique that is used to insert radioactive seeds into the prostate gland for the purpose of treatment (brachytherapy). Precision is needed to ensure that the needles are placed correctly. To achieve this, transrectal ultrasonography is used to visualize the needles, and the needles themselves are passed through holes in a template (grid) that is secured against the perineum. The perforations ensure that the needles are inserted in parallel and with a known relationship to one another. The “repurposing” of this brachytherapy technique for prostate biopsy is known as TTMB, or “grid” biopsy, and the template may be used to insert biopsy needles precisely to any location in the prostate gland. General anesthesia is recommended for patients because of the discomfort of the perineal approach and the large number of biopsy-needle insertions that are necessary to obtain an adequate number of samples from the entire prostate.
Q: What are the indications for consideration of TTMB?
A: A PSA level higher than expected for the size of the gland should prompt consideration of TTMB for better sampling of the prostate. Biopsies performed with the use of templates are important for carefully selected patients in whom there is an unexplained discordance between PSA readings and findings on examination of biopsy specimens obtained via transrectal approach. One quarter of patients who undergo TTMB after at least one negative specimen obtained by transrectal ultrasound-guided biopsy will have positive results on TTMB. Up to half of these patients have cancers with a Gleason score of 7 or higher. In patients with two or more negative specimens from transrectal ultrasound-guided biopsies, the most common finding in specimens obtained by TTMB was cancer in the anterior lobes. The morbidity associated with TTMB is greater than that associated with transrectal ultrasound-guided biopsies; there is a higher incidence of acute urinary obstruction. Overall, the costs associated with TTMB (e.g., the costs of general anesthesia, the operating room, and the processing of a large number of tissue cores) render it far more expensive than transrectal ultrasound-guided biopsies.