Correlation of magnetic resonance imaging tumor volume with histopathology.
OBJECTIVE
The biology of prostate cancer may be influenced by the index lesion. The definition of index lesion volume is important for appropriate decision making, especially for image guided focal treatment. We determined the accuracy of magnetic resonance imaging for determining index tumor volume compared with volumes derived from histopathology.


METHODS
We evaluated 135 patients (mean age 59.3 years) with a mean prostate specific antigen of 6.74 ng/dl who underwent multiparametric 3T endorectal coil magnetic resonance imaging of the prostate and subsequent radical prostatectomy. Index tumor volume was determined prospectively and independently by magnetic resonance imaging and histopathology. The ellipsoid formula was applied to determine histopathology tumor volume, whereas manual tumor segmentation was used to determine magnetic resonance tumor volume. Histopathology tumor volume was correlated with age and prostate specific antigen whereas magnetic resonance tumor volume involved Pearson correlation and linear regression methods. In addition, the predictive power of magnetic resonance tumor volume, prostate specific antigen and age for estimating histopathology tumor volume (greater than 0.5 cm(3)) was assessed by ROC analysis. The same analysis was also conducted for the 1.15 shrinkage factor corrected histopathology data set.


RESULTS
There was a positive correlation between histopathology tumor volume and magnetic resonance tumor volume (Pearson coefficient 0.633, p <0.0001), but a weak correlation between prostate specific antigen and histopathology tumor volume (Pearson coefficient 0.237, p = 0.003). On linear regression analysis histopathology tumor volume and magnetic resonance tumor volume were correlated (r(2) = 0.401, p <0.00001). On ROC analysis AUC values for magnetic resonance tumor volume, prostate specific antigen and age in estimating tumors larger than 0.5 cm(3) at histopathology were 0.949 (p <0.0000001), 0.685 (p = 0.001) and 0.627 (p = 0.02), respectively. Similar results were found in the analysis with shrinkage factor corrected tumor volumes at histopathology.


CONCLUSIONS
Magnetic resonance imaging can accurately estimate index tumor volume as determined by histology. Magnetic resonance imaging has better accuracy in predicting histopathology tumor volume in tumors larger than 0.5 cm(3) than prostate specific antigen and age. Index tumor volume as determined by magnetic resonance imaging may be helpful in planning treatment, specifically in identifying tumor margins for image guided focal therapy and possibly selecting better active surveillance candidates.
Molecular Imaging Program, National Cancer Institute, Bethesda, Maryland.
Baris
B
Turkbey
Laboratory of Pathology, National Cancer Institute, Bethesda, Maryland.
Haresh
H
Mani
Molecular Imaging Program, National Cancer Institute, Bethesda, Maryland.
Omer
O
Aras
Urologic Oncology Branch, National Cancer Institute, Bethesda, Maryland.
Ardeshir R
AR
Rastinehad
VirtualScopics, Rochester, New York.
Vijay
V
Shah
Molecular Imaging Program, National Cancer Institute, Bethesda, Maryland; Imaging Physics, SAIC Frederick, Inc., NCI-Frederick, Frederick, Maryland.
Marcelino
M
Bernardo
Division of Computational Bioscience, Center for Information Technology and Center for Interventional Oncology, NCI and Radiology, Bethesda, Maryland.
Thomas
T
Pohida
Molecular Imaging Program, National Cancer Institute, Bethesda, Maryland.
Dagane
D
Daar
Urologic Oncology Branch, National Cancer Institute, Bethesda, Maryland.
Compton
C
Benjamin
Molecular Imaging Program, National Cancer Institute, Bethesda, Maryland.
Yolanda L
YL
McKinney
Urologic Oncology Branch, National Cancer Institute, Bethesda, Maryland.
W Marston
WM
Linehan
Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, Maryland.
Bradford J
BJ
Wood
Laboratory of Pathology, National Cancer Institute, Bethesda, Maryland.
Maria J
MJ
Merino
Molecular Imaging Program, National Cancer Institute, Bethesda, Maryland.
Peter L
PL
Choyke
Urologic Oncology Branch, National Cancer Institute, Bethesda, Maryland; Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, Maryland. Electronic address: pintop@mail.nih.gov.
Peter A
PA
Pinto
D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000473:pathology*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D047368:Tumor Burden