Experience in multicatheter interstitial high-dose-rate breast brachytherapy: dose-volume histogram analysis of the first results

Purpose
To report characteristics of our treatment scheme of high-dose-rate (HDR) brachytherapy of breast cancer and to show the first outcomes of dosimetric planning analysis based on dose-volume histogram (DVH).

Material and methods
Since August 2017, 25 patients diagnosed with T1N0M0 breast cancer have received a treatment in our center. There was lumpectomy and following breast HDR brachytherapy (10 fractions of 3.4 Gy) administered to each patient. A planning target volume (PTV) and organs at risk (OARs) were recorded with DVH analysis.

Results
The study describes the full procedure of breast HDR brachytherapy with the lumpectomy. Twenty-five patients were treated, including 9 with cancer of the left breast and 16 of the right breast. The median age was 65 years. The first analysis of DVH data shows that the main OARs were ribs and skin. Mean value of D_max (ribs) for all patients was 19.90 Gy (55.88% of prescribed dose) and for the skin 30.88 Gy (90.74% of prescribed dose). During the treatment, there was only one case of toxic effects, which was pigmentation on the skin due to excess of dose limit of 1.4 Gy. Therefore, the limit exceeding of 1 Gy does not give any significant toxic effects.

Conclusions
This study is the first stage of the dosimetric evaluation of a new method. The analysis allows treating complex localizations of the breast cancer, for example, in a close position to the skin or ribs. In order to minimize the toxic effects, it is necessary to consider patient selection, catheter administration, and dose optimization.