Prostate brachytherapy postimplant dosimetry: a comparison of prostate quadrants.
OBJECTIVE
To investigate postimplant dosimetry for different regions of the prostate gland in patients treated with transperineal 125Iodine brachytherapy implants for low- and intermediate-risk prostate cancer.


METHODS
Two hundred eighty-four patients treated with permanent interstitial prostate brachytherapy comprised the study population. A nonuniform, urethral-sparing algorithm was used to plan all patients. Prostate contours were outlined on postimplant CT images. Prostate volumes were then divided into four quadrants: anterior-superior quadrant (ASQ), posterior-superior quadrant (PSQ), anterior-inferior quadrant (AIQ), and posterior-inferior quadrant (PIQ). Dose-volume histograms (DVHs) were calculated for the whole prostate and each quadrant.


RESULTS
The mean postimplant V(100) +/- 95% confidence (the percent prostate volume encompassed within the isodose surface comprising the prescription dose = 144 Gy) for the ASQ was 78.5 +/- 1.9, which was significantly lower than that of the PSQ, AIQ, and PIQ in which the V(100) plus minus 95% confidence values were 94.9 +/- 0.8, 92.6 +/- 1.2, and 98.7 +/- 0.3, respectively. The mean V(100) +/- 95% confidence for the whole prostate was 90.4 +/- 0.8. Mean values for V(150) and D(90) (the minimum dose in Gy received by 90% of the target volume) for the four quadrants and the whole prostate showed similar results.


CONCLUSIONS
Underdosed areas of the planning target volume (PTV), if present, were largely confined to the ASQ, which received a significantly lower dose, on average, compared to the other three quadrants of the prostate.
Sidhu
Sabeena
S
BC Cancer Agency, Vancouver, British Columbia, Canada.
Morris
W James
WJ
Spadinger
Ingrid
I
Keyes
Mira
M
Hilts
Michelle
M
Harrison
Robert
R
Otto
Karl
K
McKenzie
Michael
M
Agranovich
Alexander
A
D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000379:methods*; D016001:Confidence Intervals; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000033:anatomy & histology; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011879:Radiotherapy Dosage
D007457:Iodine Radioisotopes