Effects of seed migration on post-implant dosimetry of prostate brachytherapy.
Med Phys
; 34(2): 471-80, 2007 Feb.
Article
em En
| MEDLINE
| ID: mdl-17388163
ABSTRACT
Brachytherapy using permanent seed implants has been an effective treatment for prostate cancer. However, seeds will migrate after implant, thus making the evaluation of post-implant dosimetry difficult. In this study, we developed a computer program to simulate seed migration and analyzed dosimetric changes due to seed migration at various migration amounts. The study was based on 14 patients treated with Pd-103 at the James Cancer Hospital. Modeling of seed migration, including direction, distance as well as day of migration, was based on clinical observations. Changes of commonly used dosimetric parameters as a function of migration amount (2, 4, 6 mm respectively), prostate size (from 20 to 90 cc), and prostate region (central vs peripheral) were studied. Change of biological outcome (tumor control probability) due to migration was also estimated. Migration reduced prostate D90 to 99+/-2% of original value in 2 mm migration, and the reduction increased to 94+/-6% in 6 mm migration. The reduction of prostate dose led to a 14% (40%) drop in the tumor control probability for 2 mm (6 mm) migration, assuming radiosensitive tumors. However, migration has less effect on a prostate implanted with a larger number of seeds. Prostate V100 was less sensitive to migration than D90 since its mean value was still 99% of original value even in 6 mm migration. Migration also showed a different effect in the peripheral region vs the central region of the prostate, where the peripheral mean dose tended to drop more significantly. Therefore, extra activity implanted in the peripheral region during pre-plan can be considered. The detrimental effects of migration were more severe in terms of increasing the dose to normal structures, as rectum V50 may be 70% higher and urethra V100 may be 50% higher in the case of 6 mm migration. Quantitative knowledge of these effects is helpful in treatment planning and post-implant evaluation.
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Coleções:
01-internacional
Temas:
Geral
/
Tipos_de_cancer
/
Outros_tipos
/
Tratamento
/
Radioterapia
Base de dados:
MEDLINE
Assunto principal:
Neoplasias da Próstata
/
Radiometria
/
Algoritmos
/
Planejamento da Radioterapia Assistida por Computador
/
Modelos Biológicos
Tipo de estudo:
Diagnostic_studies
/
Evaluation_studies
/
Prognostic_studies
Limite:
Humans
/
Male
Idioma:
En
Revista:
Med Phys
Ano de publicação:
2007
Tipo de documento:
Article
País de afiliação:
Estados Unidos