Posterior subcapsular prostate cancer: identification with mpMRI and MRI/TRUS fusion-guided biopsy.
OBJECTIVE
The posterior subcapsular region of the prostate is often undersampled by transrectal ultrasound (TRUS)-guided biopsy. The close proximity of these lesions to the posterior capsular wall of the prostate makes them difficult to localize while increasing the need for early detection because of their increased risk for extracapsular extension. We retrospectively evaluated the multiparametric MRI (mpMRI) features of subcapsular prostate cancers to make radiologists more aware of this condition.


METHODS
Between January 2010 and July 2014, all patients referred for 3T mpMRI and subsequent MR-US Fusion-guided biopsy (FgBx) and systematic 12-core sextant biopsy (SBx) under an IRB approved protocol, were reviewed, and imaging confirmed subcapsular prostate cancers were identified. Subcapsular lesions were defined as thin lesions that were just inside the prostate capsule. Matching patient demographics and clinical findings including age, PSA, PSA density, whole prostate volume, history of prostate cancer, Gleason score, and clinical management were tabulated.


RESULTS
Of 992 eligible patients, 33 patients had subcapsular lesions in the prostate detected by mpMRI. Mean age, PSA, and prostate volume in this group were 63 years (range: 52-76 years), 8.4 ng/mL (range: 1.22-65.20), and 53 mL (range: 12-125 mL), respectively. The combination biopsy (SBx + FgBx) confirmed prostate cancer in 24 of 33 patients (72.7%) and in 9 patients the biopsy was negative. Of the 24 cancers, 19 were confirmed on both FgBx and conventional biopsy; however, 5 cancers were only detected on FgBx. In 4 of the 19 patients in which both biopsy methods were positive, the FgBx yielded a higher Gleason score.


CONCLUSIONS
Subcapsular lesions on mpMRI are relatively infrequent but are usually malignant. Although the majority are confirmed on conventional 12-core biopsies, about 20% of these lesions require FgBx for diagnosis, and FgBx more accurately grades the lesions in another 20%. Thus, FgBx is of considerable benefit in confirming the diagnosis of subcapsular prostate cancer despite their proximity to the prostatic capsule.
Molecular Imaging Program, NCI, NIH, Bethesda, MD, USA.
Sandeep
S
Sankineni
Urologic Oncology Branch, NCI, NIH, Bethesda, MD, USA.
Arvin K
AK
George
Molecular Imaging Program, NCI, NIH, Bethesda, MD, USA.
Anna M
AM
Brown
Urologic Oncology Branch, NCI, NIH, Bethesda, MD, USA.
Soroush
S
Rais-Bahrami
Center for Interventional Oncology, NCI and Radiology and Imaging Sciences, Clinical Center, NIH, Bethesda, MD, USA.
Bradford J
BJ
Wood
Laboratory of Pathology, NCI, NIH, Bethesda, MD, USA.
Maria J
MJ
Merino
Urologic Oncology Branch, NCI, NIH, Bethesda, MD, USA.
Peter A
PA
Pinto
Molecular Imaging Program, NCI, NIH, Bethesda, MD, USA.
Peter L
PL
Choyke
Molecular Imaging Program, NCI, NIH, Bethesda, MD, USA. turkbeyi@mail.nih.gov.|Molecular Imaging Program, National Cancer Institute, 10 Center Dr, MSC 1182 Bldg 10, Room B3B85, Bethesda, MD, 20892-1088, USA. turkbeyi@mail.nih.gov.
Baris
B
Turkbey
D000368:Aged; D001706:Biopsy; D006801:Humans; D008279:Magnetic Resonance Imaging; D053783:Magnetic Resonance Imaging, Interventional; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D011467:Prostate / Q000000981:diagnostic imaging / Q000473:pathology; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D018084:Ultrasonography, Interventional
Fusion guided biopsy; MRI; Prostate cancer; Subcapsular