Relationship between Day 0 dosimetric parameters and biochemical relapse-free survival in patients treated with transperineal permanent prostate interstitial brachytherapy with (125)I seeds.
OBJECTIVE
To determine the relationship between dosimetric parameters obtained on postimplantation Day 0 and biochemical relapse-free survival (bRFS) in patients treated with (125)I transperineal interstitial permanent prostate brachytherapy (TIPPB).


METHODS
Two-hundred twenty men with low-risk (n=155, 70.4%), low-volume intermediate-risk (n=63, 28.7%), or high-risk (n=2, 0.9%) prostate cancer were treated with TIPPB between December 2000 and June 2006. Seventy-four (33.6%) patients received short-term (3-6 months) androgen suppression therapy before TIPPB. The median followup for patients free of biochemical failure was of 37.9 months (range, 24.0-84.5 months).


RESULTS
The receiver operating characteristic (ROC) analysis established a best-fit cutoff value for the quantifiers D(90) and V(100) of 147Gy and 92%, respectively. The Kaplan-Meier analysis of bRFS at the cutoff value of D(90)=147Gy using the ASTRO, nadir+2, and combined (ASTRO and nadir+2) definitions showed a trend toward statistical significance for the ASTRO (p=0.076) and nadir+2 (p=0.064) definitions and a statistically significant correlation for the combined definition (p=0.033). The corresponding 7-year bRFS for the D(90) >147Gy and D(90) </=147Gy subsets using the ASTRO, nadir+2, and combined definitions were 96.5% vs. 89.7% (ASTRO, p=0.076); 93.7% vs. 70.5% (nadir+2, p=0.064); and 94.4 vs. 75.5% (combined, p=0.033). The V(100) (%) cutoff value of 92% predicted by the ROC analysis was not significant. Among other cutoff values, only D(90)=140Gy (p=0.050) and D(90)=160Gy (p=0.098) showed a trend toward statistical significance when the nadir+2 and the ASTRO definitions were used. The rest of dosimetric, tumor, and patient parameters did not show statistical correlation with bRFS in the Kaplan-Meier analysis.


CONCLUSIONS
The cutoff value of D(90)=147Gy obtained on postimplantation Day 0 showed a trend toward significant correlation with bRFS when the standard ASTRO and nadir+2 definitions were used and a weak but statistically significant correlation with bRFS as per the nonstandard combined definition in a series of patients with predominantly low-risk disease (70.4%) treated at high radiation doses (median D(90)=152.9Gy, median V(100)=92.5%).
Department of Oncology, Radiation Oncology Division, Clínica Universitaria de Navarra, Avda Pío XII s/n, Pamplona, Navarre, Spain.
Cristina
C
Garrán
Raquel
R
Ciérvide
Mauricio
M
Cambeiro
Marta
M
Moreno-Jiménez
Luis I
LI
Ramos
Rafael
R
Martínez-Monge
D000328:Adult; D000368:Aged; D000728:Androgens / Q000097:blood*; D001822:Body Burden; D001918:Brachytherapy / Q000706:statistics & numerical data*; D018572:Disease-Free Survival; D006801:Humans; D015994:Incidence; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000097:blood / Q000453:epidemiology* / Q000532:radiotherapy*; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D018570:Risk Assessment; D012307:Risk Factors; D013030:Spain / Q000453:epidemiology; D016896:Treatment Outcome
D000728:Androgens; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals