Bone metastases from prostate cancer: assessing treatment response by using diffusion-weighted imaging and functional diffusion maps--initial observations.
OBJECTIVE
To prospectively investigate and monitor the response to antiandrogen treatment of bone metastases in patients with prostate cancer by using diffusion-weighted (DW) magnetic resonance (MR) imaging with the apparent diffusion coefficient (ADC) and functional diffusion maps (DMs).


METHODS
This study had institutional review board approval; informed consent was obtained from all patients. Nine treatment-naive men (mean age, 73 years; range, 66-86 years) with 20 pelvic bone metastases were included. Imaging was performed before antiandrogen treatment and at 1, 2, and 3 months afterward. Imaging included a DW MR imaging sequence with five b factors (0-800 sec/mm²). Serum prostate-specific antigen (PSA) levels and mean ADCs of each metastasis were measured over time and analyzed by using the general linear model. Pairwise comparisons (paired-samples t tests) of PSA levels and ADCs before and after therapy were performed with the significance level set at P < .017 (Bonferroni correction). To determine the relationship between serum PSA level and the averaged mean ADCs in each patient, the two parameters were correlated across time. In addition, an analysis with functional DMs was performed to evaluate ADC response to treatment on a per-voxel basis.


RESULTS
Serum PSA levels decreased by more than 90% during therapy. The mean ADCs of metastases were increased significantly at 1 (P < .001), 2 (P = .002), and 3 (P = .011) months after therapy compared with pretreatment values. Heterogeneous response was revealed at functional DM analysis. After 1 month of therapy, 47.3% of all analyzed tumor voxels showed significantly increased ADCs, while 46.5% were unchanged and 6.2% exhibited decreased ADCs in comparison to the pretreatment values. At 3 months after therapy, the proportion of voxels showing ADC decrease was higher (13.7%) than that at 1 month.


CONCLUSIONS
DW MR imaging allows monitoring of antiandrogen therapy in bone metastases. PSA level decrease corresponded well with an increase in mean tumor ADC. Heterogeneity of tumor response to therapy was demonstrated by functional DM analysis.
Reischauer
Carolin
C
Institute for Biomedical Engineering, ETH and University Zurich, Zurich, Switzerland.
Froehlich
Johannes M
JM
Koh
Dow-Mu
DM
Graf
Nicole
N
Padevit
Christian
C
John
Hubert
H
Binkert
Christoph A
CA
Boesiger
Peter
P
Gutzeit
Andreas
A
D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D000726:Androgen Antagonists / Q000627:therapeutic use; D001859:Bone Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D016014:Linear Models; D008297:Male; D010384:Pelvic Bones / Q000000981:diagnostic imaging / Q000473:pathology*; D011446:Prospective Studies; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000473:pathology*; D011877:Radionuclide Imaging; D051598:Whole Body Imaging
D000726:Androgen Antagonists; D017430:Prostate-Specific Antigen