I'll try to answer some of your questions.
With regards to radiation therapy in patients with DCIS, it really depends on the pathological characteristics of the tumor itself. You are correct in that not all patients are required to undergo radiation therapy after lumpectomy, but if it's being recommended it's likely that there is something about the pathology that is concerning for risk of local recurrence without radiation.
With regards to SAVI, SAVI is a very new technology that is being used at many centers to replace wire localization in lumpectomy. Traditionally, if a patient opts for lumpectomy, a wire is place around the area of concern, or the titanium clip, and this provides the surgeon a means of knowing exactly how much breast tissue to remove. Once the lumpectomy is completed, an X-ray of the specimen is obtained and the surgeon can verify that the mammographic abnormality has been removed. To do that, a wire is placed the morning of surgery very similar to the way the biopsy was obtained. SAVI allows for a marker that can be placed instead, up to 30 days prior to surgery. Surgeons are then able to use a probe in the OR to tract the SAVI capsule and ensure an adequate resection. SAVI is only placed after the patient has a diagnosis of malignancy and has opted for lumpectomy. The reasons for that are multiple but namely: the 30 day lifespan of the SAVI capsule and the fact that not all patients will require a subsequent surgery after a stereotactic or US guided biopsy. Not to mention the fact that not all patients will opt for lumpectomy or are even candidates for lumpectomy. To use SAVI on every patient who receives a biopsy would be a waste of medical resources.
I hope that answers your questions and sending best wishes to your sister on her cancer journey.
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