Dr. Leonard Marks and colleagues at the University of California, Los Angeles were among the earliest groups to start to use and publish data on MRI/TRUS fusion biopsies of the prostate. They have now reported some early data on repeat biopsies using such methodology in men on active surveillance.
The paper by Sonn et al. in Urologic Oncology provides data on initial and repeat biopsies, under MRI/TRUS fusion guidance, of patients who were all given an initial biopsy and a repeat biopsy between March 2010 and January 2013. The men’s initial biopsies all included 12 cores based on a standard template (which were mapped using proprietary software) and directed biopsies from regions of interest seen on an MRI. In the repeat biopsies, samples were taken exclusively from sites known to have been cancerous on the initial biopsy. The researchers applied an electronic tracking system (the Artemis technology) to track the original biopsy data and to plan the repeat MRI/TRUS fusion-guided biopsies.
Here are the core findings of the study:
- 53 men underwent an initial MRI/TRUS fusion-guided biopsy and were found to have prostate cancer with clinical stage T1c.
- These 53 men had a total of 74 positive biopsy cores on initial biopsy.
- 63/74 cores (85 percent) were Gleason 3 + 3 = 6.
- 11/74 cores (15 percent) were Gleason 3 + 4 = 7.
- 51/74 cores (69 percent) were found on systematic 12-core biopsy data.
- 23/74 cores (31 percent) were found within an MRI-targeted area.
- On repeat MRI/TRUS fusion biopsy
- 29/74 positive cores (39 percent) were again detected.
- There was no correlation between Gleason score of the original core and re-detection on the repeat biopsy.
- Re-detection on repeat biopsy was directly related to the length of the cancerous region of the original biopsy core (P < 0.02).
- 9 of the re-biopsied sites showed an increase in Gleason score
- Of the cancerous regions identified on repeat MRI/TRUS fusion biopsy
- 61 percent were in regions found in the MRI targeted areas found to be positive on initial biopsy.
- 29 percent were in regions found on the initial 12-core, systematic biopsy.
- When a patient’s initial cancer core length was ≥ 4 mm and had been identified by MRI targeting, 5/6 follow-up biopsies (83 percent) were positive.
Sonn et al. conclude that:
Monitoring of specific prostate cancer-containing sites may be achieved in some men using an electronic tracking system. The chances of finding tumor on repeat specific-site sampling was directly related to the length of tumor in the initial biopsy core and presence of tumor within an MRI target; upgrading of Gleason score was uncommon.
It has to be said, however, that these conclusions are based on data from a very small number of patients, and that the re-identification of only 29/74 positive cores found on the original biopsy is a little worrisome.
The authors claim that only 9/74 original biopsy cores (12 percent) showed an increase in Gleason score, which would be very promising if we knew that it was absolutely true. Another way to look at these data would be to say that 9/29 positive biopsy cores re-identified on re-biopsy (31 percent) showed an increase in Gleason score and that the technique used failed to re-identify the presence of cancer in 45/74 regions of the prostate that were originally cancerous. It is certainly possible that 45/74 of the cancers found in the original biopsies went into spontaneous remission, but this does seem to be a little on the unlikely side. The question that is therefore raised by these data is, just how good is the electronic tracking system and related software in assuring a precise re-biopsy of the region that was originally found to be biopsy-psoitive?
It is hard to know exactly what to make of these data reported by Sonn et al. It is certainly true that, as they are also careful to note in their conclusions:
Further research is required to evaluate the potential utility of site-specific biopsy tracking for patients with prostate cancer on active surveillance.