Susan Richardson
Medical Physicist, Swedish Cancer Institute

The use of permanent breast brachytherapy using Pd-103 seeds has been well documented as a safe and efficacious treatment method for early stage breast cancers in Canadian trials. As an alternative to other partial breast irradiation techniques such as 3D conformal radiotherapy or HDR Brachytherapy, this treatment is performed in a single outpatient procedure in the operating room. This is particularly attractive for patients who travel long distances to receive treatment. The technique has recently been marketed in the United States by Concure Oncology (Breast Microseed Treatment®).

Previous implementations of this technique have used ultrasound imaging with a breast probe to localize the post-lumpectomy target on treatment day. We have modified this protocol to use linac based CBCT to localize the target based on post-surgical clips. Patient positioning is aided through the use of a surface mapping system (Catalyst-HDTM) to help position the arms and head of the patient. Finally, the MLCs of the linac are used to project the treatment planning outline of the target volume on the patient’s surface. The target volume is then accurately drawn on the patient’s skin before transferring the patient to the OR for interstitial implant. Compared to the original method of drawing the target on the skin based on ultrasound imaging, this method positions the patient within a millimeter and uses localization techniques that radiation therapy staff are more familiar with.

This talk will describe both the permanent LDR breast brachytherapy method and the localization techniques using CBCT and Catalyst surface mapping.


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