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 (猢?.5 cm3) 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.
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 1.4 mm (range, 0-12). Expanding the contour by 5 mm at the non-capsular margin included 95% of tumor volume not initially covered within the MR contour.
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 5 mm.