Extraprostatic (extracapsular) extension of prostate cancer refers to local tumor growth beyond the fibromuscular band surrounding the prostate gland. It is a pathological finding important to prostate cancer staging.
Though imperfect, MRI is superior to transrectal ultrasound, CT, and digital rectal examination in predicting the likelihood of extracapsular extension.
Morphologic predictors of extraprostatic extension at MRI are listed in rough order from most specific to most sensitive 1,3,4:
- seminal vesicle invasion (asymmetric loss of normal high T2 signal in the seminal vesicular lumen)
- neurovascular asymmetry (unequal appearance of neurovascular bundles when ipsilateral tumor is present)
- frank capsular breach (tumor clearly extends into the periprostatic fat or invades adjacent organs such as rectum or bladder)
- obliteration of the rectoprostatic angle (loss of fatty space between prostate and rectum; posteriorly located tumors only)
- capsular bulge (smooth or irregular convex outward protrusion of prostate margin continuous with tumor)
- broad capsular contact (≥10-20 mm in curvilinear length of contact between tumor and capsule) 1,5-7
Treatment and prognosis
On preoperative imaging, the suggestion of extraprostatic extension is important for surgical planning and counseling as resection of the neurovascular bundle may be required.
Extraprostatic extension is associated with higher risk of recurrence and metastasis and lower cancer-specific survival after radical prostatectomy 1.
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