Viewpoint: A Magic Wand?

When a patient is eligible for accelerated partial-breast irradiation (APBI), there is a strong need for collaboration between the radiation oncologist and the diagnostic radiologist prior to starting treatment. Routine communication is required to discuss additional abnormalities or other potentially malignant sites in the breast, as well as to share information about available treatment options.

Given the promising research regarding the new SAVI applicator for breast brachytherapy, it is essential that radiology professionals are aware of the device’s significant advantages over other methods for delivering APBI.

The SAVI™ applicator, developed by Aliso Viejo, Calif.-based Cianna Medical Inc., is currently in use at several 21st Century Oncology radiation therapy centers throughout the country.

Our early research suggests that the single-entry, multi-catheter device provides superior dose control, and this control offers clear benefit for our patients. The unique design of the applicator allows for a more precise delivery of radiation, with the promise to increase the number of women who can benefit from APBI.

Advantages of APBI

Until recently, lumpectomy, followed by radiation of the entire breast, was a standard treatment for early-stage breast cancer. However, the six to seven weeks of daily treatments required for whole-breast irradiation places a significant burden on patients.

In fact, the difficulties associated with such a prolonged treatment are cited as one of the reasons that up to 30 percent of women who undergo lumpectomy do not follow through with radiation therapy.

Fortunately, APBI is now considered a viable option in lieu of traditional whole breast radiation for many patients diagnosed with early-stage breast cancer. The most common form of APBI is breast brachytherapy, in which the tumor cavity is treated with a radiation source from within the breast.

An internal device allows for the delivery of radiation to the appropriate areas, while safely reducing the length of treatment to just five days. APBI enables patients to receive a safe and effective course of radiation, but without the inconvenience of a lengthy treatment.

Evolution of APBI

The earliest form of APBI was interstitial brachytherapy. With this method, multiple catheters are inserted in the breast, allowing physicians to tailor the radiation dose based on the patient’s anatomy. While the ability to customize the dose is a significant advantage, each catheter has its own entry and exit point. 

This makes it a technically complicated procedure that requires a high level of clinical expertise. Intracavitary (“balloon”) brachytherapy consists of one catheter attached to a balloon that is inserted into the breast through a single incision. A single radiation source is placed inside the balloon, distributing a spherically symmetrical dose of radiation to the tissue.

Placement of the single-entry balloon is a far simpler procedure than interstitial brachytherapy. However, the inability to customize the dose is a limiting factor, and therefore it is not always an appropriate treatment option for certain patients.

In my experience, approximately one-third of APBI patients are ineligible for treatment with balloon brachytherapy, due to technical restrictions. For patients without adequate spacing between the tumor and the skin, chest wall or other organs, the balloon would expose all tissue – regardless of whether it contains cancer – to equally high doses of radiation.

Without the ability to precisely target radiation, the balloon is contraindicated in these situations. The SAVI applicator is a relatively new technology for delivering APBI. The device consists of a bundle of catheters that is inserted into the breast in a collapsed position. As with balloon brachytherapy, SAVI requires just a single incision in the breast.

Once the applicator is inserted, the physician expands the catheters to conform to the shape of the tumor cavity; each catheter utilizes its own radiation source. This design enables physicians to minimize radiation exposure to healthy structures and better focus radiation into the breast tissue where it is needed to destroy cancer cells and prevent recurrences.

The “hybrid” design of SAVI combines the advantages of interstitial brachytherapy and balloon brachytherapy. Like the balloon, SAVI is inserted through a single incision in the breast, making it far easier than introducing multiple catheters.

Like interstitial, the device’s multiple catheters offer a dosimetric advantage over single-catheter devices by providing greater control of the radiation distribution, based on patient-specific anatomy. By targeting the radiation more precisely, SAVI treats the tissue where cancer is most likely to recur, while minimizing the exposure of healthy tissue, such as the skin, chest wall or lungs.

SAVI is an important development in the field of radiation therapy, with the potential to expand the benefits of APBI to a larger group of women. Its open-architecture design eliminates skin-spacing limitations, making it suitable for treating small, large, and irregularly shaped cavities. With its superior dose control, SAVI allows some patients – who would otherwise be ineligible for APBI with the balloon – to receive breast brachytherapy.

Early Experiences with SAVI

I presented the results of 21st Century Oncology’s early experiences with the SAVI applicator in a poster at the 2008 Miami Breast Cancer Conference. We examined the first 18 patients treated with SAVI at 21st Century Oncology, and found that the device’s superior dose control resulted in a low rate of toxicities, particularly in the skin.

Though skin reactions are a common side effect of radiation therapy, 14 out of the 18 patients treated with SAVI experienced no skin reactions. Of the four patients who experienced reactions, all were minor cases that were quickly resolved, without the need for additional care.

These findings demonstrate that greater control over the delivery of radiation results in a safe, effective treatment that is well-tolerated by a majority of women studied. In addition, our trial confirms the potential for the SAVI applicator to expand the number of women eligible for APBI.

In the study, 10 out of 18 patients would have been ineligible for treatment with the balloon, due to limited spacing between the tumors and the skin. The more accurate delivery of radiation with SAVI enables physicians to offer this more expedient form of treatment to a larger number of medically eligible patients.

Our early experiences also demonstrate that SAVI significantly reduces the risk of seroma formation during treatment. In the trial, seroma was not observed in 15 of the 18 patients. In addition to improving cosmetic outcomes following treatment, a lack of seroma can simplify subsequent imaging of the breast.

Seroma often complicates follow-up mammograms for the interpreting radiologist, as it tends to resemble a mass and may require additional ultrasonic imaging to rule out malignancy. Less seroma typically allows for better imaging of the tumor bed, enhancing a radiologist’s ability to detect local recurrences on future mammograms. 

The Next Generation of Radiation Therapy

To date, 21st Century Oncology has successfully treated 65 patients with the SAVI applicator. We see SAVI as offering a better option for clinical care, as the device benefits surgeons and radiation oncologists. For breast surgeons, SAVI simplifies the decision when choosing the modality with which to deliver radiation.

Previous technical restrictions – such as the size, shape or location of the cavity – are much less of a factor with SAVI, allowing surgeons to simply focus on whether or not patients are medically eligible for APBI. Radiation oncologists benefit because the device gives them far greater control over the distribution of the radiation dose.

The multiple catheters allow them to pull dose away from nearby critical structures and push it farther into the tissue where it is needed. At 21st Century Oncology, we consider the SAVI applicator to be the next generation of radiation therapy.

SAVI is technically easy to use, while providing excellent coverage of the tumor cavity and sparing as much normal tissue as possible. Its impact on the APBI arena is potentially large, as it opens the treatment to a greater number of patients who otherwise would not have been eligible for this advantageous form of radiation therapy.


— Constantine Mantz, MD, is a radiation oncologist at 21st Century Oncology, based in Fort Myers, Fla. Direct all comments and questions to editorial@rt-image.com.