Postoperative nomogram predicting the 9-year probability of prostate cancer recurrence after permanent prostate brachytherapy using radiation dose as a prognostic variable.
OBJECTIVE
To report a multi-institutional outcomes study on permanent prostate brachytherapy (PPB) to 9 years that includes postimplant dosimetry, to develop a postimplant nomogram predicting biochemical freedom from recurrence.


METHODS
Cox regression analysis was used to model the clinical information for 5,931 patients who underwent PPB for clinically localized prostate cancer from six centers. The model was validated against the dataset using bootstrapping. Disease progression was determined using the Phoenix definition. The biological equivalent dose was calculated from the minimum dose to 90% of the prostate volume (D90) and external-beam radiotherapy dose using an alpha/beta of 2.


RESULTS
The 9-year biochemical freedom from recurrence probability for the modeling set was 77% (95% confidence interval, 73-81%). In the model, prostate-specific antigen, Gleason sum, isotope, external beam radiation, year of treatment, and D90 were associated with recurrence (each p < 0.05), whereas clinical stage was not. The concordance index of the model was 0.710.


CONCLUSIONS
A predictive model for a postimplant nomogram for prostate cancer recurrence at 9-years after PPB has been developed and validated from a large multi-institutional database. This study also demonstrates the significance of implant dosimetry for predicting outcome. Unique to predictive models, these nomograms may be used a priori to calculate a D90 that likely achieves a desired outcome with further validation. Thus, a personalized dose prescription can potentially be calculated for each patient.
Potters
Louis
L
Department of Radiation Medicine, North Shore Long Island Jewish Health System, 270-05 76th Ave., New Hyde Park, NY 11040, USA. LPotters@nshs.edu
Roach
Mack
M
Davis
Brian J
BJ
Stock
Richard G
RG
Ciezki
Jay P
JP
Zelefsky
Michael J
MJ
Stone
Nelson N
NN
Fearn
Paul A
PA
Yu
Changhong
C
Shinohara
Katsuto
K
Kattan
Michael W
MW
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000379:methods*; D018450:Disease Progression; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000097:blood / Q000175:diagnosis*; D049451:Nomograms; D011336:Probability; D011379:Prognosis; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D012044:Regression Analysis
D017430:Prostate-Specific Antigen