Novel prostate brachytherapy technique: improved dosimetric and clinical outcome.
OBJECTIVE
Erectile dysfunction following prostate brachytherapy is reported to be related to dose received by the penile bulb. To minimise this, whilst preserving prostate dosimetry, we have developed a technique for I-125 seed brachytherapy using both stranded seeds and loose seeds delivered with a Mick applicator, and implanted via the sagittal plane on trans-rectal ultrasound.


METHODS
Post-implant dosimetry and potency rates were compared in 120 potent patients. In Group 1, 60 patients were treated using a conventional technique of seeds implanted in a modified-uniform distribution. From January 2005, a novel technique was developed using stranded seeds peripherally and centrally distributed loose seeds implanted via a Mick applicator (Group 2). The latter technique allows greater flexibility when implanting the seeds at the apex. Each patient was prescribed a minimum peripheral dose of 145 Gy. No patients received external beam radiotherapy or hormone treatment. There was no significant difference in age or pre-implant potency score (mean IIEF-5 score 22.4 vs. 22.6, p=0.074) between the two groups.


RESULTS
The new technique delivers lower penile bulb doses (D(25) as %mPD - Group 1: 61.2+/-35.7, Group 2: 29.7+/-16.0, p<0.0001; D(50) as %mPD - Group 1: 45.8+/-26.9, Group 2: 21.4+/-11.7, p<0.0001) whilst improving prostate dosimetry (D(90) - Group 1: 147 Gy+/-21.1, Group 2: 155 Gy+/-16.7, p=0.03). At 2 years, the potency rate was also improved: Group 1: 61.7%; Group 2: 83.3% (p=0.008).


CONCLUSIONS
In this study, the novel brachytherapy technique using both peripheral stranded seeds and central loose seeds delivered via a Mick applicator results in a lower penile bulb dose whilst improving prostate dosimetry, and may achieve higher potency rates.
Nobes
Jenny P
JP
St. Luke's Cancer Centre, The Royal Surrey County Hospital, Guildford, UK. jpnobes@gmail.com
Khaksar
Sara J
SJ
Hawkins
Maria A
MA
Cunningham
Melanie J
MJ
Langley
Stephen E M
SE
Laing
Robert W
RW
D001918:Brachytherapy / Q000009:adverse effects / Q000379:methods*; D007172:Erectile Dysfunction / Q000209:etiology*; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D010413:Penis / Q000528:radiation effects; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D018709:Statistics, Nonparametric; D016896:Treatment Outcome; D018084:Ultrasonography, Interventional
D007457:Iodine Radioisotopes