A Contura™ catheter provides dosimetric advantages over a MammoSite™ catheter for accelerated partial breast irradiation.

Abstract

#5141 Purpose/Objective(s): With the new ConturaTM Multi-Lumen Balloon (MLB) catheter (SenoRx, Inc, Aliso Viejo, CA), one may achieve 2 dosimetric advantages over a MammoSiteTM catheter: 1) avoidance of a radiation “hot spot” in the skin which may improve cosmetic results, and 2) reduction of the size of an air/fluid pocket in the planning target volume for plan evaluation (PTV_EVAL) which may improve local control by increasing the radiation dose delivered to breast tissue at risk. The purpose of this study was to analyze the frequency with which a Contura catheter can satisfy the above 2 dosimetric goals relative to a MammoSite catheter.
 Materials/Methods: From October 2007 to June 2008, 23 patients between the ages of 43 and 88 years (median, 57 years) with unifocal AJCC pathological T0, T1, or T2 (maximum, 3.0 cm; median, 1.0 cm), N0 ductal, papillary, or tubular carcinomas of the breast at least 1 mm from the inked edge of the lumpectomy specimen were treated with high-dose-rate iridium-192 brachytherapy using a Contura MLB catheter. Sixty-five percent of the cancers were estrogen-receptor positive. Brachytherapy was delivered to a total dose of 34 Gy in 10 fractions bid over 5-7 days. We prescribed the dose to a depth of 1.0 cm from the balloon surface. The Contura applicator allows one to load up to 5 source lumens: 4 lumens that are offset 0.5 cm circumferentially from a central lumen. The ability to choose from multiple lumens allows for greater control over where radiotherapy is delivered. The Contura catheter also has a sixth lumen through which air/fluid can be removed from around the balloon. This feature helps to improve tissue-balloon conformance. The minimum balloon-to-skin distance was 0.5 cm. In 39% of patients, the balloon-to-skin distance was 0.5-0.9 cm. The balloon volume was 30-55 cc, V150 was ≤ 33 cc, and V200 was ≤ 10 cc. Hypothetical MammoSite treatment plans were created using a CT scan of the breast prior to air/fluid removal. Only the central lumen was loaded for the hypothetical MammoSite plan. The 2 treatment planning goals were to keep the: 1) maximum skin dose ≤ 100% of the prescribed dose, and 2) volume of air/fluid around the balloon ≤ 3.0% of PTV_EVAL. A one-sided McNemar test was used to compare the % of Contura plans that satisfied both goals vs the % of MammoSite plans that satisfied both goals.
 Results: The maximum skin dose was 100% of the prescribed dose with the Contura catheter vs 145% of the prescribed dose with a MammoSite catheter. The volume of air/fluid around the balloon was 4.4% ± 1.0% (mean ± standard error) of PTV_EVAL prior to suctioning vs 1.2% ± 0.3% after suctioning. Ninety-one percent of Contura plans satisfied both treatment planning goals vs only 48% of MammoSite plans (p=0.08).
 Conclusion: A Contura applicator resulted in a trend towards dosimetric improvement over a MammoSite catheter. Patients will be followed long-term in order to determine their local control, disease-free survival, cosmetic results, and treatment-related toxicities. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5141.