Is your current prostate biopsy doing enough?

The authors evaluated the usefulness of transition zone prostate biopsy in prostate cancer patients undergoing active surveillance.

The peripheral zone of the prostate is the area of the prostate that is closest to the rectum, and is easily felt by the doctor during a digital rectal examination. Approximately 75-80% of prostate tumors are found in this zone. The remaining cancers are located in the transition zone, the middle area of the prostate between the peripheral zone and central zone (the part farthest from the rectum). Typically the transition zone is not sampled during prostate biopsy (removal of prostate tissue to analyze for cancer cells). However, in men undergoing active surveillance (close observation of cancer rather than immediate treatment), it may be important to consider unsampled regions of the transition zone which could potentially harbor significant cancer.

This study investigated the impact of routine transition zone biopsy in a group of men under active surveillance for prostate cancer.

392 men were included in the study. Typically men had a prostate-specific antigen (PSA) level of less than 10 ng/mL, a stage of cT2 or less (early stage cancer), Gleason score of 6 or less (early stage cancer), 3 or fewer tissue core samples testing positive for cancer and age 75 years or less.

Biopsies were undertaken via transrectal ultrasound guided prostate biopsy (an ultrasound probe is inserted into the back passage to allow imaging of the prostate gland, following which a needle is inserted via the probe to take small samples of the prostate gland). Initial biopsies sampled only the peripheral zone, and further biopsies evaluated both the peripheral and transition zones. Average follow-up after the first biopsy was 45.5 months.

At the second biopsy 11.9% of men had cancer progression (increased growth and invasiveness of the cancer), and this increased to 20.5% by the fifth biopsy. At the second biopsy 18.6% of men had positive cores on transition zone biopsy, and this increased to 26.7% by the fifth biopsy. 2.7% of men had progression only in the transition zone at the second biopsy, increasing to 6.7% at the fifth biopsy. Of those who showed progression during transition zone-inclusive biopsies, 66% had cancer progression exclusively in the transition zone.

Maximum percentage of a single core involved (cancer present in more than 70% of a single core sample) was associated with 99% increased risk of transition zone progression. Positive transition zone biopsy cores were associated with an 88% increased risk of transition zone progression. Diagnosis of cancer via magnetic resonance imaging (an MRI; uses a magnetic field and pulses of radio wave energy to make pictures of organs and structures inside the body) was associated with 3.19 times the risk of progression exclusively in the transition zone and 76% increase in combined transition zone and peripheral zone progression.

Increasing numbers of biopsies after the second biopsy were associated with a 40% reduction in the risk of transition zone cancer, a 48% reduction in the risk of all transition zone progression and 41% reduction in the risk of exclusively transition zone progression.  

The authors state that their findings suggest that transition zone biopsy should be considered at confirmatory biopsy in all men.