Prostate cancer: effect of postbiopsy hemorrhage on interpretation of MR images.
OBJECTIVE
To assess the frequency of changes in signal intensity after prostatic biopsy and the effect of these changes on the magnetic resonance (MR) imaging staging of prostate cancer.


METHODS
Seventy-three patients with biopsy-proved prostate cancer were divided into two groups according to time between biopsy and imaging (less than and more than 21 days). The findings at MR imaging were compared with those at pathologic examination.


RESULTS
Postbiopsy hemorrhage was detected in 21 of 26 (81%) patients who underwent imaging less than 21 days after biopsy and in 23 of 47 (49%) patients who underwent imaging more than 21 days after biopsy (P < .01). Postbiopsy changes persisted for as long as 4 1/2 months. Less than 21 days after biopsy, there was a tendency to overestimate tumor presence and extracapsular extension. After 21 days, tumor presence was underestimated but the positive predictive value for extracapsular extension was improved. Staging accuracy less than 21 days after biopsy was 46%; this improved to 83% after 21 days (P < .01).


CONCLUSIONS
Staging accuracy is significantly improved when imaging is deferred for 21 days after biopsy.
White
S
S
Department of Radiology, University of California, San Francisco 94143-0628, USA.
Hricak
H
H
Forstner
R
R
Kurhanewicz
J
J
Vigneron
D B
DB
Zaloudek
C J
CJ
Weiss
J M
JM
Narayan
P
P
Carroll
P R
PR
D001707:Biopsy, Needle / Q000009:adverse effects*; D005188:False Negative Reactions; D005189:False Positive Reactions; D006470:Hemorrhage / Q000209:etiology / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011237:Predictive Value of Tests; D011467:Prostate / Q000473:pathology*; D011469:Prostatic Diseases / Q000209:etiology / Q000473:pathology; D011471:Prostatic Neoplasms / Q000473:pathology*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013997:Time Factors