Dosimetric characteristics of the MammoSite RTS, a new breast brachytherapy applicator

The purpose of this study is to dosimetrically compare two plans generated using single dwell position method (SDPM) and multiple dwell position methods (MDPM) in MammoSite high dose rate (HDR) brachytherapy planning for 19 breast cancer patients. In computed tomography (CT) image‐based HDR planning, a surface optimization technique was used in both methods. Following dosimetric parameters were compared for fraction 1 plans: %PTV_EVAL (planning target volume for plan evaluation) coverage, dose homogeneity index (DHI), dose conformal index (COIN), maximum dose to skin and ipsilateral lung, and breast tissue volume receiving 150% (V150[cc]) and 200% (V200[cc]) of the prescribed dose. In addition, a plan was retrospectively generated for each fraction 2–10 to simulate the clinical situation where the fraction 1 plan was used for fractions 2–10 without modification. In order to create nine derived plans for each method and for each of the 19 patients, the catheter location and contours of target and critical structures were defined on the CT images acquired prior to each fraction 2–10, while using the same dwell‐time distribution as used for fraction 1 (original plan). Interfraction dose variations were evaluated for 19 patients by comparing the derived nine plans (each for fractions 2–10) with the original plan (fraction 1) using the same dosimetric parameters used for fraction 1 plan comparison. For the fraction 1 plan comparison, the MDPM resulted in slightly increased %PTV_EVAL coverage, COIN, V150[cc] and V200[cc] values by an average of 1.2%, 0.025, 0.5 cc and 0.7 cc, respectively, while slightly decreased DHI, maximum skin and ipsilateral lung dose by an average of 0.003, 3.2 cGy and 5.8 cGy, respectively. For the interfraction dose variation comparison, the SDPM resulted in slightly smaller variations in %PTV_EVAL coverage, DHI, maximum skin dose and V150[cc] values by an average of 0.4%, 0.0005, 0.5 cGy and 0.2 cc, respectively, while slightly higher average variations in COIN, maximum ipsilateral lung dose and V200[cc] values by 0.0028, 0.2 cGy and 0.2 cc, respectively. All differences were too small to be clinically significant. Compared to the MDPM, the SDPM combined with a surface optimization technique can generate a clinically comparable fraction 1 treatment plan with a similar interfraction dose variation if a single source is carefully positioned at the center of the balloon catheter.PACS number: 87.53.Jw

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparison of single and multiple dwell position methods in MammoSite high dose rate (HDR) brachytherapy planning

Kim

Trombetta

Miften

2010

“…In 2002, the FDA approved the use of the MammoSite single‐entry balloon (Hologic, Bedford, MA) which greatly increased the interest in brachytherapy‐based APBI. The original MammoSite protocol used a single catheter with a single central dwell point to treat a 1 cm rind of tissue surrounding the lumpectomy site (5) . A phase III clinical trial was initiated to study the efficacy of APBI as compared to conventional whole‐breast irradiation (6) .…”

Section: Introductionmentioning

confidence: 99%

Contralateral breast dose from partial breast brachytherapy

Robinson

Nelson

Bloom

et al. 2015

The purpose of this study was to determine the dose to the contralateral breast during accelerated partial breast irradiation (APBI) and to compare it to external beam‐published values. Thermoluminescent dosimeter (TLD) packets were used to measure the dose to the most medial aspect of the contralateral breast during APBI simulation, daily quality assurance (QA), and treatment. All patients in this study were treated with a single‐entry, multicatheter device for 10 fractions to a total dose of 34 Gy. A mark was placed on the patient's skin on the medial aspect of the opposite breast. Three TLD packets were taped to this mark during the pretreatment simulation. Simulations consisted of an AP and Lateral scout and a limited axial scan encompassing the lumpectomy cavity (miniscan), if rotation was a concern. After the simulation the TLD packets were removed and the patients were moved to the high‐dose‐rate (HDR) vault where three new TLD packets were taped onto the patients at the skin mark. Treatment was administered with a Nucletron HDR afterloader using Iridium‐192 as the treatment source. Post‐treatment, TLDs were read (along with the simulation and QA TLD and a set of standards exposed to a known dose of 6 MV photons). Measurements indicate an average total dose to the contralateral breast of 70 cGy for outer quadrant implants and 181 cGy for inner quadrant implants. Compared to external beam breast tangents, these results point to less dose being delivered to the contralateral breast when using APBI.PACS number: 87.55.D‐

“…If used as a monotherapy, the treatment with the MammoSite device is generally 34 Gy delivered in 10 fractions (3.4 Gy/fraction twice daily) at 1.0 cm from the balloon surface with a minimum of 6 hours between fractions on the same day. ( 1 , 2 ) …”

Section: Introductionmentioning

confidence: 99%

The impact of uncertainties associated with MammoSite brachytherapy on the dose distribution in the breast

Bensaleh

Bezak

2011

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