Salvage radiotherapy for rising prostate-specific antigen levels after radical prostatectomy for prostate cancer: dose-response analysis.
OBJECTIVE
To investigate the association between external beam radiotherapy (EBRT) dose and biochemical failure (BcF) of prostate cancer in patients who received salvage prostate bed EBRT for a rising prostate-specific antigen (PSA) level after radical prostatectomy.


METHODS
We evaluated patients with a rising PSA level after prostatectomy who received salvage EBRT between July 1987 and October 2007. Patients receiving pre-EBRT androgen suppression were excluded. Cox proportional hazards models were used to investigate the association between EBRT dose and BcF. Dose was considered as a numeric variable and as a categoric variable (low, <64.8 Gy; moderate, 64.8-66.6 Gy; high, >66.6 Gy).


RESULTS
A total of 364 men met study selection criteria and were followed up for a median of 6.0 years (range, 0.1-19.3 years). Median pre-EBRT PSA level was 0.6 ng/mL. The estimated cumulative rate of BcF at 5 years after EBRT was 50% overall and 57%, 46%, and 39% for the low-, moderate-, and high-dose groups, respectively. In multivariable analysis adjusting for potentially confounding variables, there was evidence of a linear trend between dose and BcF, with risk of BcF decreasing as dose increased (relative risk [RR], 0.77 [5.0-Gy increase]; p = 0.05). Compared with the low-dose group, there was evidence of a decreased risk of BcF for the high-dose group (RR, 0.60; p = 0.04), but no difference for the moderate-dose group (RR, 0.85; p = 0.41).


CONCLUSIONS
Our results suggest a dose response for salvage EBRT. Doses higher than 66.6 Gy result in decreased risk of BcF.
Bernard
Johnny Ray
JR
Department of Radiation Oncology, Mayo Clinic, Jacksonville, FL 32224, USA.
Buskirk
Steven J
SJ
Heckman
Michael G
MG
Diehl
Nancy N
NN
Ko
Stephen J
SJ
Macdonald
Orlan K
OK
Schild
Steven E
SE
Pisansky
Thomas M
TM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004307:Dose-Response Relationship, Radiation; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016016:Proportional Hazards Models; D017430:Prostate-Specific Antigen / Q000097:blood*; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000097:blood* / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D016879:Salvage Therapy / Q000379:methods*; D013997:Time Factors
D017430:Prostate-Specific Antigen