Postimplantation analysis enables improvement of dose-volume histograms and reduction of toxicity for permanent seed implantation.
OBJECTIVE
To demonstrate how postimplantation analysis is useful for improving permanent seed implantation and reducing toxicity.


METHODS
We evaluated 197 questionnaires completed by patients after permanent seed implantation (monotherapy between 1999 and 2003). For 70% of these patients, a computed tomography was available to perform postimplantation analysis. The index doses and volumes of the dose-volume histograms (DVHs) were determined and categorized with respect to the date of implantation. Differences in symptom scores relative to pretherapeutic status were analyzed with regard to follow-up times and DVH descriptors. Acute and subacute toxicities in a control group of 117 patients from an earlier study (June 1999 to September 2001) by Wust et al. (2004) were compared with a matched subgroup from this study equaling 110 patients treated between October 2001 and August 2003.


RESULTS
Improved performance, identifying a characteristic time dependency of DVH parameters (after implantation) and toxicity scores, was demonstrated. Although coverage (volume covered by 100% of the prescription dose of the prostate) increased slightly, high-dose regions decreased with the growing experience of the users. Improvement in the DVH and a reduction of toxicities were found in the patient group implanted in the later period. A decline in symptoms with follow-up time counteracts this gain of experience and must be considered. Urinary and sexual discomfort was enhanced by dose heterogeneities (e.g., dose covering 10% of the prostate volume, volume covered by 200% of prescription dose). In contrast, rectal toxicities correlated with exposed rectal volumes, especially the rectal volume covered by 100% of the prescription dose.


CONCLUSIONS
The typical side effects occurring after permanent seed implantation can be reduced by improving the dose distributions. An improvement in dose distributions and a reduction of toxicities were identified with elapsed time between 1999 and 2003.
Wust
Peter
P
Department of Radiation Oncology, Charité Universitätsmedizin Berlin, Berlin, Germany. peter.wust@charite.de
Postrach
Johanna
J
Kahmann
Frank
F
Henkel
Thomas
T
Graf
Reinhold
R
Cho
Chie Hee
CH
Budach
Volker
V
Böhmer
Dirk
D
D001918:Brachytherapy / Q000009:adverse effects / Q000379:methods / Q000592:standards*; D006306:Health Surveys; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011795:Surveys and Questionnaires; D013997:Time Factors; D047368:Tumor Burden