Use of MRI and spectroscopy in evaluation of external beam radiotherapy for prostate cancer.
OBJECTIVE
To characterize the metabolic response in the prostate, the time to resolution of disease, and the correlation between magnetic resonance imaging (MRI) with spectroscopy (MRSI) results, biopsy findings, and serum prostate-specific antigen (PSA) level after external beam radiotherapy.


METHODS
A total of 55 patients underwent MRSI before and/or at varying times after external beam radiotherapy. The percentage of the cancerous, healthy, and atrophic voxels was calculated, and the time to resolution of disease was determined and compared with the PSA nadir.


RESULTS
Of the 55 patients, 70% had negative MRSI and 30% had positive MRSI findings. A strong correlation was found between negative MRSI and negative biopsy findings (n = 11) and between positive MRSI and positive biopsy findings (n = 7). A weak correlation was observed between the PSA level and the MRSI and biopsy findings. The mean time to disease resolution was 40.3 months and the mean time to PSA nadir was 50 months. With time, an increase in atrophy and a decline in cancerous metabolism was found.


CONCLUSIONS
When used in conjunction with PSA measurement and biopsy, the results of this study suggest that MRSI contributes to a greater level of confidence in determining the outcome and may be a useful adjunct for assessing local control before PSA failure when striving to distinguish the benign "blip" from local recurrence.
Pickett
Barby
B
Department of Radiation Oncology, University of California, San Francisco, School of Medicine, San Francisco, CA, USA. pickett@radonc17.ucsg.edu
Kurhanewicz
John
J
Coakley
Fergus
F
Shinohara
Katsuto
K
Fein
Beverly
B
Roach
Mack
M
D000726:Androgen Antagonists / Q000627:therapeutic use; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use; D001707:Biopsy, Needle / Q000379:methods; D006801:Humans; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D011467:Prostate / Q000473:pathology; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000175:diagnosis / Q000378:metabolism* / Q000532:radiotherapy*; D020266:Radiotherapy, Conformal; D013997:Time Factors
D000726:Androgen Antagonists; D018931:Antineoplastic Agents, Hormonal; D017430:Prostate-Specific Antigen