Robert Hong, MD
The largest toxicity study of patients who have received accelerated partial breast irradiation (APBI) with the SAVI® (Strut-Adjusted Volume Implant) applicator was presented by radiation oncologist Robert Hong, MD at the 54th annual meeting of the American Society for Radiation Oncology (ASTRO). Reporting on 515 patients, including 100 patients with four years of follow up, Dr. Hong concluded that SAVI showed excellent local control and had favorably low rates of complications such as seroma, hyperpigmentation and telangiectasia.
The data was drawn from the SAVI Collaborative Research Group, which includes over 1,000 patients from 14 sites across the U.S. and represents the largest subset of patients who have received APBI with the SAVI applicator.
Dr. Hong discusses the latest study from the SAVI Collaborative Research Group, including how the results compare to other forms of breast brachytherapy and what they mean for the future of strut-based brachytherapy.
The study demonstrates favorable toxicity profiles for strut-based brachytherapy – what do you attribute these low rates of both acute and late toxicities to?
The ability of the SAVI device to modulate the dose enables us to minimize toxicities. The design of the device allows us to achieve effective skin sparing and improve dose coverage to a larger portion of the volume at risk, which likely contributed to the good outcomes. The symptomatic fat necrosis rate was under one percent, which is tremendous, and the symptomatic seroma rate was 2.6 percent. Overall, the rates of late toxicities never exceeded 3.1 percent, which is very good and compares favorably to the data for balloon devices.
I also attribute the lower rates of toxicities to more experience. The strut-based device comes at a time where we’ve learned from our initial experience with intracavitary brachytherapy, both surgically and from a radiation oncology perspective. Factors like better patient selection and improved surgical techniques have also contributed to better outcomes.
How does the occurrence of toxicities compae to other breast brachytherapy devices?
The toxicity with strut-based brachytherapy is minimal and comparable to, if not better than, the rates published for first-generation balloon brachytherapy devices. With a symptomatic toxicity of less than 4 percent, in comparison to any other brachytherapy device or procedure, that’s extremely low. In our study, the rate of symptomatic seroma was 2.6 percent, which is very favorable to a rate of 10 percent or more at two years as shown in some published data for balloon brachytherapy. In terms of toxicities, if we’re comparing first-generation strut-based brachytherapy with the SAVI device to first-generation balloon brachytherapy, SAVI wins hands down.
How can physicians effectively communicate the results of this and similar studies to patients when presenting them with their radiation treatment options?
When discussing treatment options with patients, I would inform them that this study, which includes over 100 patients with four years of follow-up, demonstrates that the SAVI device is just as safe and effective as any other device that is approved for the delivery of APBI. I would also mention that the flexibility of SAVI allows for dose sculpting to minimize unnecessary radiation to critical structures. As a result of this flexibility, SAVI also opens the door for more patients to choose this treatment option, allowing us to treat women who would otherwise be technically ineligible for APBI, whether it’s due to small breast or cavity size, cavity location close to the skin or chest wall, or other situations, such as breast implants, that would make it very difficult, if not impossible, for a balloon catheter to deliver radiation.
What do the results of your study mean for the future application of strut-based brachytherapy?
This particular piece of research represents the largest toxicity report of APBI using SAVI, which is very significant. It shows that strut-based brachytherapy is not only efficacious, with a 98 percent local control rate, but also that toxicity is very low. I think physicians who begin to introduce partial breast irradiation into daily clinical practice for eligible patients should include strut-based brachytherapy in their repertoire of techniques, and it should be considered a standard option for women who choose to undergo APBI.
In particular, the low rate of fat necrosis is important to note. Strut-based brachytherapy has sometimes been criticized because the struts are adjacent to the target tissue, which can modestly increase the volume of normal tissue receiving 200 percent of the prescription dose. Previously, the assumption had been that moderate volumes of tissue receiving higher doses of radiation results in higher rates of fat necrosis, but that idea has been negated by this study. We have demonstrated that strut-based brachytherapy enables us to sufficiently modulate the dose so that the symptomatic fat necrosis rate remains very low, regardless of V200 levels.
Dr. Hong is a radiation oncologist at the Virginia Hospital Medical Center in Arlington, VA. He has published widely and is a frequent presenter on topics such as breast cancer, head and neck cancer, lung cancer and functional imaging such as PET scans. He has been recognized for his expertise in medical informatics, as well as in gynecologic and prostate brachytherapy with prestigious awards from the American College of Radiation Oncology and the American Brachytherapy Society.