Abstract
The MammoSite radiation therapy system is a novel technique for treatment of patients with early‐stage breast cancer. It was developed to overcome the longer schedules associated with external‐beam radiation therapy. It consists of a small balloon (4 cm in diameter) connected to an inflation channel and a catheter for the passage of a high dose rate 192Ir brachytherapy source. The device is placed into the tumor resection cavity and inflated with a mixture of saline and radiographic contrast agent to a size that fills the cavity. A high dose rate 192Ir source is driven into the balloon center using a remote afterloader to deliver the prescribed dose at a point 1 cm away from the balloon surface. There are several uncertainties that affect the dose distribution in the MammoSite brachytherapy. They include source position deviation, balloon deformation, and the concentration of the contrast medium inside the balloon. The purpose of this study is to investigate the extent of the dose perturbation for various concentrations of the contrast medium in a MammoSite balloon using Monte Carlo simulations and thermoluminescent dosimetry. This study also combines the impact of these uncertainties on the MammoSite treatment efficacy. The current study demonstrates that the combined uncertainties associated with the MammoSite brachytherapy technique — up to the value of 2 mm balloon deformation, 1 mm source deviation, and 15% contrast concentration — have no impact on the tumor control probability.PACS number: 87.53.‐j
Highlights
In the management of early-stage (I or II) breast cancer, breast-conserving surgery followed by radiotherapy is an alternative treatment to mastectomy for patients who desire breast preservation
The TLD chips used in the current study had the advantages of small size (0.38 mm thickness) and dose rate independence which would make them good detectors for dose measurements with the high dose rate (HDR) source
The Monte Carlo simulations were based on CT data which resembles patient geometry, as opposed to other studies where the Monte Carlo calculations were performed in a water phantom
Summary
In the management of early-stage (I or II) breast cancer, breast-conserving surgery followed by radiotherapy is an alternative treatment to mastectomy for patients who desire breast preservation. The MammoSite radiation therapy system (Hologic, Inc., Marlborough, MA), is a relatively new brachytherapy procedure for accelerated partial breast irradiation. It is being used as an alternative to whole breast external beam irradiation for treatment of patients with early-stage breast cancer. There are recommendations regarding the patient selection for the MammoSite treatment. It is used for treatment of patients diagnosed with ductal carcinoma in situ (DCIS), invasive ductal carcinoma (IDC), and a primary tumor of size ≤ 3 cm. The main advantage of this technique is the high conformal dose deposition in the target volume and sparing of the organs at risk due to the influence of the inverse square law effect on the dose distribution around the source
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