GLEASON
SCORE AND LATERALITY CONCORDANCE BETWEEN PROSTATE BIOPSY AND PROSTATECTOMY
SPECIMENS
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KENNETH G. NEPPLE, TERRY L. WAHLS, STEPHEN L. HILLIS, FADI N. JOUDI
Department of Urology (KGN, FNJ), University of Iowa, Iowa City, Department of Surgery (FNJ), Veterans Affairs, Iowa City Health Care System, Center for Research in the Implementation of Innovative Strategies in Practice (TLW, SLH), Iowa City, Iowa, USA
ABSTRACT
Objectives:
Prostate biopsy involvement and Gleason score guide treatment decisions
in prostate cancer. We evaluated concordance in Gleason score and laterality
between biopsy and radical retropubic prostatectomy (RRP) specimens and
factors that influenced this relationship.
Materials and Methods: We reviewed 538 prostate
cancer diagnoses at a Veterans Affairs medical center (2000-2005) to identify
men with prostate biopsy and RRP specimens. During this time there was
a move from limited (6 core) to extended (12 core) biopsy schemes. Discordance
in Gleason score was defined as any change in Gleason score.
Results: 152 men underwent RRP with biopsy
showing Gleason < 7 in 56%, 7 in 36%, and > 7 in 8%. Biopsy involvement
was unilateral in 59% and bilateral in 41%. Compared to the biopsy, RRP
Gleason score was concordant in 76 (50%), higher in 51 (34%), and lower
in 25 (16%). Bilateral involvement was concordant in 97%, while unilateral
involvement was concordant in only 20%. Both Gleason score and laterality
were concordant in only 26%. Gleason concordance was higher in those with
8 or more cores compared to < 8 cores taken (54% vs. 34%, p = 0.046),
but concordance was not affected by age, PSA, prostate volume, or length
of time from biopsy to RRP. During later years, concordance did not improve
despite taking more cores.
Conclusions: Prostate biopsy underestimated
prostatectomy Gleason score in 34% of men and bilateral involvement in
80% of those with unilateral disease on biopsy. Taking at least eight
cores improves the accuracy of the prostate biopsy.
Key
words: prostate neoplasms; biopsy; prostatectomy
Int Braz J Urol. 2009; 35: 559-64
INTRODUCTION
Prostate
cancer is common in men with an estimated 218,890 new diagnoses and 27,050
deaths in 2007 (1). The pathologic diagnosis of prostate cancer is based
on transrectal ultrasound guided prostate biopsy which provides information
on Gleason grade and unilateral versus bilateral cancer involvement. Gleason
grade and prostate biopsy involvement subsequently guide treatment decisions,
and influence surgical decisions with respect to nerve-sparing and pelvic
lymph node dissection at the time of radical retropubic prostatectomy
(RRP). Because of a trend in the PSA era toward patients presenting with
low PSA levels and nonpalpable disease, pretreatment Gleason score may
be the most important prognostic factor for treatment response and patient
outcome (2).
It is important for clinicians to have information regarding the accuracy
of prostate biopsy specimens. Prior studies have suggested that taking
more prostate cores may improve the concordance between biopsy and prostatectomy
(2-5), while others have not found such a relationship (6). Our main study
objective was to evaluate concordance of Gleason score and laterality
between prostate biopsy and RRP specimens in a cohort of our patients.
A secondary objective was to evaluate whether an increased number of cores
improved concordance.
MATERIALS AND METHODS
We retrospectively
reviewed 538 prostate cancer diagnoses at the Veterans Affairs Medical
Center Iowa City from 2000-2005 to identify men who underwent RRP. Patients
were excluded if prostatectomy was not performed or if pathology reports
from both prostate biopsy and RRP specimens were not available. Prostate
biopsies were obtained using transrectal ultrasound guidance and the number
of cores taken was at the discretion of the clinician. Clinical and pathologic
data was reviewed for information including pathology reports from prostate
biopsy and RRP. PSA value prior to biopsy was used for analysis. Number
of days from initial biopsy to RRP was calculated for each patient. We
defined concordance as an exact match in grade (or laterality) from biopsy
to corresponding RRP specimen. Discordance was defined as a difference
in grade (or laterality) from biopsy to RRP (i.e. upgrading from Gleason
3+4 to 4+3 was considered discordant).
Analysis was performed using the chi-square or Fisher’s exact test
for categorical variables and the Wilcoxon rank sum test for ordinal or
continuous variables. P < 0.05 was considered significant. Statistical
analysis was performed using SigmaStat 3.5. Institutional Review Board
approval for the study was obtained.
RESULTS
Of the 538 men diagnosed with prostate cancer during the index period (2000-2005), 152 met inclusion criteria and underwent RRP (Table-1). Prostate biopsy was Gleason < 7 in 56%, 7 in 36%, and > 7 in 8%. Biopsy involvement was unilateral in 90 (59%) and bilateral in 62 (41%). During the time period of this study, there was a general move from limited (6 core) to extended (12 core) biopsy schemes (Figure-1).
Average age at RRP was 61.3 years (median 61.2, range 44.1 to 74.5). Compared
to biopsy, RRP Gleason score was concordant in 76 (50%), upgraded in 51
(34%), and downgraded in 25 (16%). Of those 51 patients who had Gleason
score upgraded on RRP, Gleason grade was increased by < 1 grade in
7, 1 grade in 39, and > 1 grade in 5 patients. In the 25 patients who
had Gleason score downgraded on RRP, Gleason grade was decreased by <
1 grade in 10, 1 grade in 13, and > 1 grade in 2 patients.
Concordance was not affected by age, PSA, prostate volume, or length of
time from biopsy to RRP (Table-2). However, differences were noted for
Gleason sum 7 biopsies, as Gleason 3+4 concordance was 67% (30 of 45)
with upgrading in 22% (10 of 45) and downgrading in 11% (5 of 45) versus
Gleason 4+3, which was concordant in none (0 of 10) with upgrading in
20% (2 of 10) and downgrading in 80% (8 of 10) (p < 0.001).
Gleason concordance was higher in those with 8 or more cores compared
to < 8 cores taken (54% vs. 34%, p = 0.046). Table-3 shows the concordance
rate stratified by number of cores. The highest accuracy rate was in the
group with 8-9 cores, with a statistically significant improvement in
accuracy from 34% to 64% seen when going from 5-7 to 8-9 cores (p = 0.03).
Despite the increase in cores taken per patient in each subsequent year
during our study (Figure-1), an incremental increase in accuracy over
time was not observed (Table-4).
When biopsy involvement was unilateral, 72 of 90 (80%) actually had bilateral
involvement on RRP (Figure-2). In patients with bilateral biopsy involvement,
60 of 62 (97%) had bilateral involvement on prostatectomy. Both Gleason
score and laterality were concordant in only 26%.
COMMENTS
Findings
on prostate biopsy can differ from findings on RRP, and accurate assessment
of prostate cancer on biopsy is important because it guides treatment
decisions. Patients with low-grade prostate cancer are more likely to
be offered expectant management without active treatment (7). Patients
with higher grade involvement on prostate biopsy are more likely to have
pelvic lymph node dissection performed and less likely to be offered nerve-sparing
prostatectomy. We evaluated patients who underwent prostatectomy, and
found that prostate biopsy underestimated Gleason score in 34% of men
and bilateral involvement in 80% of those with unilateral disease on biopsy.
These differences may be due to sampling error, pathologist’s interpretation,
or disease progression (8).
In our study, there was a general trend toward increased concordance when
more prostate core biopsies were performed as the concordance rate was
lowest in the 5-6 core group. Prior studies have suggested that taking
more prostate cores may improve the concordance between biopsy and prostatectomy
(2-5), while others have argued that more cores does not improve prognostic
information (6). Coogan et al. reported 10 cores provided an accuracy
of 58% versus 40-41% in those with 8 and 6 cores (4). San Francisco et
al. reported an extended biopsy regimen with 10 or more cores improved
concordance from 63% to 76%, and also proposed that processing each prostate
core separately also improved accuracy (3). Similarly, Mian et al. noted
improvement in accuracy from 48% to 68% when more than 6 cores were taken
(2). One study of 100 consecutive prostatectomy specimens evaluated by
core biopsy of the surgical specimens on the bench top reported that prostate
cancer detection improved from 75% with sextant biopsies to 88% with an
extended 14 core biopsy (9).
Despite the suggestion that taking more cores directly leads to increased
accuracy, the relationship is likely multi-factorial. Toward the later
years of our study, more prostate cores were taken and accuracy declined,
but was still improved compared to taking sextant biopsies. One possible
explanation for this finding would be the change in pathologists’
interpretation of the biopsy specimens. Sampling error can also be a contributing
factor.
There are limitations to our study, including those inherent in a retrospective
analysis. There was a general trend toward taking more core biopsies during
the study period; however this was not done with a standardized protocol.
The pathology review for this study was not performed by a single pathologist,
and during review of prostatectomy specimens the pathologist was not blinded
to the initial biopsy involvement, which could have influenced interpretation.
CONCLUSIONS
Prostate biopsy underestimated prostatectomy Gleason score in 34% of men and bilateral involvement in 80% of those with unilateral disease on biopsy. Taking at least eight cores improves the accuracy of the prostate biopsy.
ACKNOWLEDGEMENTS
This study
is supported in part by funding from the Center for Research in the Implementation
of Innovative Strategies in Practice (CRIISP), United States Department
of Veterans Affairs.
The views expressed in this article are those of the authors and do not
necessarily reflect the policy or position of the Department of Veterans
Affairs.
CONFLICT OF INTEREST
None declared.
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- Nesrallah L, Nesrallah A, Antunes AA, Leite KR, Srougi M: The role of extended prostate biopsy on prostate cancer detection rate: a study performed on the bench. Int Braz J Urol. 2008; 34: 563-70; discussion 570-1.
____________________
Accepted after revision:
May 25, 2009
_______________________
Correspondence address:
Dr. Fadi N. Joudi
Dept. of Urology, University of Iowa
200 Hawkins Dr., 3 RCP
Iowa City, IA 52242-1089, USA
Fax: + 1 319 356-3900
E-mail: fadi-joudi@uiowa.edu