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IMAGING
Extraprostatic
spread of clinically localized prostate cancer: factors predictive of
pT3 tumor and of positive endorectal MR imaging examination results
Cornud F, Flam T, Chauveinc L, Hamida K, Chrétien Y, Vieillefond
A, Hélénon O, Moreau JF
Departments of Radiology and Urology, Hôpital Necker, Department
of Urology, Hôpital Cochin, and Department of Radiotherapy, Institut
Pierre et Marie Curie, Paris, France
Radiology 2002; 224:203-10
- Purpose:
To
identify the factor(s) most predictive of pT3 tumor and those most predictive
of a positive endorectal magnetic resonance (MR) imaging result in patients
with clinically localized prostate cancer.
- Materials
and Methods:
At multivariate analysis, five preoperative clinical parameters—prostate-specific
antigen (PSA) level, digital rectal examination (DRE) result, Gleason
score and number of involved sextants at transrectal US–guided
biopsy, and endorectal MR imaging result—were used to predict pT3
tumor in 336 patients who underwent radical prostatectomy. On the basis
of results of the first four examinations, multivariate analysis was
performed also to determine predictors of a positive MR imaging study.
- Results:
Significant
predictors of pT3 tumor were positive MR imaging result (P<2 x 10-8),
more than one sextant involved at biopsy (P<5 x 10-5), and PSA level
greater than 10 ng/mL (P<7 x 10-3). Significant predictors of a positive
MR imaging result were three or more sextants involved at biopsy (P<10-5),
positive DRE result (P<5 x 10-3), and PSA level greater than 10 ng/mL
(P<16 x 10-3). In the subgroup of 175 patients who had at least three
positive biopsy specimens, the sensitivity of MR imaging was 50% for
detection of occult pT3 tumor and 69% for detection of extensive pT3
tumor. The overall specificity of MR imaging was 95%.
- Conclusion:
Endorectal MR imaging seems to be indicated in carefully selected patients
- specifically, those with 3 or more positive biopsy specimens, a palpable
tumor, and/or a PSA level greater than 10 ng/mL.
- Editorial
Comment
There is still much controversies among urologists, whether endorectal
MR imaging should or should not be used for staging prostate cancer.
Although the number of urologists that use this method has been growing,
this group is still a minority. The main reason for that is because
they believe that MR imaging is not sensitive or specific enough to
predict extraprostatic disease. There are several reasons to explain
this situation: lack of consensus among radiologists regarding what
are the specific signs of extraprostatic disease, the use of different
equipments and different techniques thus resulting in distinct degree
of accuracy, and MR imaging readers with no particular training and/or
interest in uroradiology. All these factors are responsible for the
significant differences in accuracy showed by several reports in the
literature during the last decade.
The authors presented a rare prospective study where a multivariate
analysis of 5 pre-operative clinical parameters(PSA, DRE, Gleason score,
and number of positive sextants biopsies) was performed in a large series
of 336 patients who underwent radical prostatectomy. The positive aspect
of this study is that MRI was used in the best conditions in order to
optimize its results and consequently obtain the maximum specificity
possible. These conditions include: a)- experienced uroradiologists,
b)- exclusion of indirect signs of extraprostatic extension and sole
use of direct signs of capsular disruption or seminal vesicle invasion,
c)- use of combination of endorectal coil and anterior surface coil,
and d)- knowledge of all clinical information available before reading
the MR imaging examination (DRE result, PSA level and sites of positive
transrectal ultrasound biopsies). By using these criteria, the authors
achieved a 95% specificity for MR imaging and as one should expect this
high specificity was only accomplished at a cost of an undesirable relatively
low sensitivity.
After the study performed by D’Amico et al. (1), showing the limitations
of using the Partin’s probability plots and nomograms (2) the criteria
for utilization of MR imaging for staging clinically localized prostate
cancer has been changed. According the study by Partin et al, the risk
of extraprostatic extension in these group of patients can be determined
by the combination of DRE result, PSA level, and Gleason score. Results
of the D’Amico study, demonstrated that in the group of patients
with intermediate risk of pT3 tumor, as defined on the basis of a PSA
level of 11-20ng/ml and Gleason score 5 -7, the addition of MRI increased
the efficiency of extraprostatic tumor detection (overall accuracy 78-80%),
relative to the elements indicated by Partin. Since the percentage of
positive biopsy specimens(calculated on the number of sextants invaded
by tumor), indirectly reflects tumor volume(3) and its propensity for
extraprostatic extension, the authors applied this variable to patients
with intermediate risk of extraprostatic disease pT3 tumors. Multivariate
analysis results showed that the presence of at least 3 positive specimens
was the most powerful predictor of a positive MR imaging result and
also a useful tool to identify patients with a risk of extensive extraprostatic
disease.
This manuscript confirmed previous studies by showing that endorectal
MR imaging is a reliable method of predicting occult extraprostatic
disease but, this method should not be used as a routine procedure in
all patients with clinically localized prostate cancer. On contrary,
it should be reserved for a selected group of patients.
References
1. D’Amico AV, Whittington R, Schnall M: The impact of the inclusion
of endorectal coil magnetic resonance imaging in a multivariate analysis
to predict clinically unsuspected extraprostatic cancer. Cancer 1995;
75:2368-72.
2. Partin AW, Yoo J, Carter HB: The use of prostate specific antigen,
clinical stage and Gleason score to predict pathological stage in men
with localized prostate cancer. J Urol. 1993; 150:110-4.
3. Ackerman DA, Barry JM, Wicklund RA, Olson N, Lowe BA. Analysis of risk
factors associated with prostate cancer extension to the surgical margin
and pelvic node metastasis at radical prostatectomy. J Urol. 1993; 150:1845-50.
Dr. Adilson Prando
Department of Radiology
Vera Cruz Hospital
Campinas, São Paulo, Brazil
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