Dr. Robert Hong, from the Virginia Hospital Center in Arlington, presented a study at ASTRO this year entitled, Factors Improving Skin Sparing, Rib Sparing, and D95 Dose Coverage in Accelerated Partial Breast Irradiation Across Five Catheter Subtypes. The study analyzed different methods for performing brachytherapy in an effort to discern advantages and disadvantages.
Hong's team knew that using balloon and strut-based applicators could achieve excellent results but wanted to see how they compared.
Unlike external beam radiation oncology, brachytherapy for partial breast irradiation involves implanting a catheter that houses a temporary radioactive source in the space where the tumor has been surgically removed. Hong and his colleagues see untapped potential in the internal therapy and their study yielded promising outcomes from their catheter comparison.
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"We're talking about the location of the source relative to the edges of the lumpectomy cavity which you're prescribing the dose to," said Hong in an interview with DOTmed News. The dose prescription should cover a one centimeter rim of tissue beyond where the tumor was removed. With balloon-based catheters, Hong said you would hypothetically deliver the dose with a lower hot spot to the surface, "because the dose is attenuated via the distance from the source in the center to the edge of the balloon." Conversely, a strut-based catheter implants the radiation directly adjacent to the tissue at risk, so technically it creates a hotter hot spot.
"What we found," said Hong, "is that while the initial hot spot may theoretically be hotter, the flexibility of the multiple channels and the multiple dwell positions afforded by the struts allow us greater opportunity dosimetrically to spare the skin, the rib, and achieve equal dose coverage to other devices." In terms of outcomes, Hong said there's no difference, but in terms of device flexibility, Hong believes the strut-based implants perform better.
Knowing your options
Candidacy for brachytherapy depends on specific clinical circumstances. "For early stage low risk breast cancer patients who have undergone breast-conserving surgery, such as a lumpectomy," Hong thinks those women may be equally suitable for brachytherapy as for external beam. Hong and his colleagues feel the treatment may be underutilized on potential candidates.
While most of Hong's patients who are eligible for brachytherapy will choose to undergo the treatment, he says some clients choose beam therapy because they wish to avoid undergoing another invasive procedure. Hong believes what's important is that patients are given the necessary information to make the right choice for themselves. He suspects that overall, brachytherapy is an underutilized option.