Role of endorectal MR imaging and MR spectroscopic imaging in defining treatable intraprostatic tumor foci in prostate cancer: quantitative analysis of imaging contour compared to whole-mount histopathology.
OBJECTIVE
To investigate the role of endorectal MR imaging and MR spectroscopic imaging in defining the contour of treatable intraprostatic tumor foci in prostate cancer, since targeted therapy requires accurate target volume definition.


METHODS
We retrospectively identified 20 patients with prostate cancer who underwent endorectal MR imaging and MR spectroscopic imaging prior to radical prostatectomy and subsequent creation of detailed histopathological tumor maps from whole-mount step sections. Two experienced radiologists independently reviewed all MR images and electronically contoured all suspected treatable (≥0.5 cm(3)) tumor foci. Deformable co-registration in MATLAB was used to calculate the margin of error between imaging and histopathological contours at both capsular and non-capsular surfaces and the treatment margin required to ensure at least 95% tumor coverage.


RESULTS
Histopathology showed 17 treatable tumor foci in 16 patients, of which 8 were correctly identified by both readers and an additional 2 were correctly identified by reader 2. For all correctly identified lesions, both readers accurately identified that tumor contacted the prostatic capsule, with no error in contour identification. On the non-capsular border, the median distance between the imaging and histopathological contour was 1.4mm (range, 0-12). Expanding the contour by 5mm at the non-capsular margin included 95% of tumor volume not initially covered within the MR contour.


CONCLUSIONS
Endorectal MR imaging and MR spectroscopic imaging can be used to accurately contour treatable intraprostatic tumor foci; adequate tumor coverage is achieved by expanding the treatment contour at the non-capsular margin by 5mm.
Department of Radiation Oncology, University of California San Francisco, USA. Electronic address: anwarme@radonc.ucsf.edu.
Mekhail
M
Anwar
Department of Radiology and Biomedical Imaging, University of California San Francisco, USA.
Antonio C
AC
Westphalen
Department of Radiology and Biomedical Imaging, University of California San Francisco, USA.
Adam J
AJ
Jung
Department of Radiology and Biomedical Imaging, University of California San Francisco, USA; UCSF Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, USA; The Graduate Group in Bioengineering, University of California San Francisco, USA; University of California Berkeley, USA.
Susan M
SM
Noworolski
Department of Anatomic Pathology, University of California San Francisco, USA; UCSF Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, USA.
Jeffry P
JP
Simko
Department of Radiology and Biomedical Imaging, University of California San Francisco, USA; UCSF Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, USA; The Graduate Group in Bioengineering, University of California San Francisco, USA; University of California Berkeley, USA.
John
J
Kurhanewicz
Department of Radiation Oncology, University of California San Francisco, USA; UCSF Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, USA.
Mack
M
Roach
Department of Urology, University of California San Francisco, USA; UCSF Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, USA.
Peter R
PR
Carroll
Department of Radiology and Biomedical Imaging, University of California San Francisco, USA; Department of Urology, University of California San Francisco, USA; UCSF Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, USA.
Fergus V
FV
Coakley
D000368:Aged; D003952:Diagnostic Imaging / Q000379:methods; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000601:surgery; D012189:Retrospective Studies; D047368:Tumor Burden
Dominant intraprostatic lesion; Dose escalation; Focal therapy; MRI; MRSI; Prostate cancer