First and second biopsies and their diagnostic accuracy


A paper by Wong et al. published in December carries the title, “Diagnostic prostate biopsy performed in a non-academic center increases the risk of re-classification at confirmatory biopsy for men considering active surveillance for prostate cancer.”

It would be easy from the title of this paper to get the idea that clinicians at academic medical centers are necessarily “better” at the conduct of prostate biopsies than clinicians in community practices, but that is not necessarily a valid conclusion at all.

What Wong et al. actually did was report the results of a retrospective analysis of data from patients who — between 1997 and 2012 — had both a diagnostic biopsy (B1), carried out at either a community practice or at their tertiary teaching institution, and then a second “eligibility” biopsy (B2) prior to assignment to management on an institutional active surveillance protocol. All the “eligibility” biopsies were conducted at the tertiary teaching institution.

All the patients were ≤ 75 years of age and met standardized criteria such that they were known to be eligible for management on active surveillance: PSA < 10 ng/ml; Gleason score ≤ 6; clinical stage ≤ cT2; three or fewer positive biopsy cores; < 50 percent of any single core exhibiting cancer.

The question the research team asked was whether, if the diagnostic biopsy (B1) was being performed at an external, community center (as opposed to at the tertiary teaching institution), this increased the risk of re-classification on the second (confirmatory) biopsy (B2), which was always carried out at the teaching institution.

They did indeed find this was the case. Specifically, they found that

  • 71/375 patients (18.9 percent) received B1 in the community setting.
  • 304/375 patients (81.1 percent received B1 at the tertiary teaching institution.
  • When patients got their second biopsy (B2) at the teaching institution
    • 19/71 patients (26.8 percent) initially diagnosed in a community setting were re-classified.
    • 42/304 patients (13.8 percent initially diagnosed at the teaching institution were re-classified).
    • This difference was statistically significant (P = 0.008).
  • They also found that when B1 was carried out in the community setting, this predicted
    • Gleason grade-related re-classification with an odds ratio (OR) = 4.14 (P < 0.001)
    • Cancer volume-related re-classification with an OR = 3.43 (P < 0.001).
  • Other significant predictors for grade-related re-classification were
    • Patient age (OR = 2.13 per decade; P < 0.001)
    • PSA density (OR = 2.56 per unit; P < 0.001)
    • Maximum  percentage of core involvement (OR = 1.04 per percentage point; P = 0.02)
    • Time between B1 and B2 (OR = 1.43 per 6 months; P < 0.001).

The authors draw a simple and very reasonable conclusion:

At our institution, patients on [active surveillance] who had their initial B1 performed externally were more likely to have adverse pathological features and re-classify on internal B2.

This should not actually come as any sort of major surprise.

Why?

For any one or more of all the following reasons:

  • Patients receiving B1 at the tertiary center were probably all receiving that initial biopsy according to one standardized institutional protocol, whereas men being diagnosed in the community would have been diagnosed according to multiple slightly different protocols.
  • Patients receiving B1 at the tertiary center were likely to be given biopsies by highly trained specialists who carried out hundreds of biopsies a year (or trainees being carefully supervised by such specialists).
  • Patient receiving biopsies at an external community center might have their biopsy specimens assessed at any one of many possible pathology laboratories (by individuals with varying skill levels) as opposed to a single, specialized uropathologist at the tertiary center.
  • All patients receiving a B2 biopsy to see if he was eligible to enter an active surveillance protocol would inevitably be biopsied with greater care and caution than a patient might be on first biopsy. The B2 biopsy is designed to seek out and identify any reason why a patient might not be eligible for active surveillance. The B1 biopsy is only intended to see if there is any sign of prostate cancer at all.

Are there differences in the skill levels at which individual urologists are able to carry out prostate biopsies? Sure there are. Absolutely. However, this does not mean that there aren’t skilled, community-based urologists who are very good indeed at carrying out prostate biopsies — especially if they are qualified as board certified urologic oncologists. Such specialized urologists are probably sending their biopsy specimens to one of the recognized major uropathology centers for assessment. On the other hand, there are many general urologists who see far fewer men at risk for prostate cancer on a day to day basis than they may see women and children with a wide range of urological complaints. Such urologists simply don’t do as many prostate biopsies; they probably don’t expect to treat the patient themselves; and their goal is only to diagnose the cancer and refer the patient to a specialist for treatment.

On top of this, as observed by a clinician quoted in a report on this paper on the Medscape web site, there is now a strong argument that any patient being re-biopsied to see if he is eligible for inclusion on an active surveillance protocol should have that second biopsy carried out under some form of direct MRI or MRI/TRUS fusion guidance. THis, in and of itself, will increase the probability of finding cacner that may not have been evident on an initial biopsy.

In the view of The “New” Prostate Cancer InfoLink, it is not necessarily the case that everyone who thinks he might be at risk for prostate cancer needs to go rushing off to the The Cleveland Clinic or to the Princess Margaret Hospital in Toronto to get an initial biopsy. They do need to check whether they are seeing a urologist who, if at all possible, is someone who sees, biopsies, and diagnoses men for risk of prostate cancer on a regular and frequent basis (but even that may not be so easy if you live in the wilds of Montana or similar). And if you want to consider active surveillance (or focal therapy of some type) as a management strategy for low-risk prostate cancer, then you would certainly be wise to take yourself to a center that has extensive experience in the evaluation and management of men on such protocols, and get re-biopsied at such a center (ideally under MRI/TRUS fusion guidance or similar) bu someone who has real experience in the biopsy of these types of patient.

One Response

  1. Another factor is the equipment used. Typically major research centers have newer if not more innovative scanning equipment.

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