Dosimetric characteristics of the MammoSite RTS, a new breast brachytherapy applicator.
OBJECTIVE
A new device has been developed with the goal of making breast-conserving therapy more widely available, by making breast brachytherapy as monotherapy simpler and more accurate. This is the first published report on the dosimetric characteristics of this device.


METHODS
The experience of a single institution participating in a multi-institutional trial is reported. Twelve patients were enrolled, of whom 8 were treated. Computed tomography scans of all 12 patients were obtained before initiation of treatment. A commercial three-dimensional planning system was used for retrospective detailed analysis of dosimetry, including dose-volume histograms and, in selected patients, skin dose distributions. These data were compared to those of a similar group of patients, analyzed previously, that was treated with interstitial high-dose-rate brachytherapy.


RESULTS
Compared with interstitial brachytherapy, the MammoSite device resulted in a treatment dose that was less uniform, with a mean dose homogeneity index of 0.77 vs. 0.93. Coverage and reproducibility were improved, with a mean D90 (minimum dose to 90% of target volume) of 90.0% of prescribed dose (SD 0.5, range: 89.2-90.8%) vs. 69.8% (SD 7.3, range: 61.1-83.5%) for interstitial brachytherapy.


CONCLUSIONS
Reproducible placement was easily achieved in this very early experience, indicating a much smaller "learning curve" than for interstitial brachytherapy. Because skin doses can be increased with the use of this device, caution is indicated, although simple maneuvers can significantly reduce skin dose.
Edmundson
Gregory K
GK
Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, MI 48073, USA. gedmundson@beaumont.edu
Vicini
Frank A
FA
Chen
Peter Y
PY
Mitchell
Christina
C
Martinez
Alvaro A
AA
D001918:Brachytherapy / Q000295:instrumentation*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental; D055585:Physical Phenomena; D010825:Physics; D011859:Radiography; D011879:Radiotherapy Dosage; D015203:Reproducibility of Results