The small, early study reviewed here reports preliminary results on a new way to deliver internal radiation therapy (also called brachytherapy) that doesn't use radioactive material. The new technique is called the Axxent system and it successfully delivered the specified dose of radiation therapy to 44 women so far.
Axxent system side effects were similar to side effects from other forms of internal radiation therapy.
The results were presented at the 2008 American Society of Clinical Oncology (ASCO) Breast Cancer Symposium.
Radiation therapy is commonly used after early breast cancer surgery to destroy any cancer cells that may have been left behind and to reduce the risk of the cancer coming back. Radiation therapy can be delivered by an external beam of radiation aimed at the area where the cancer used to be. This is called external radiation. Radiation therapy also can be delivered by placing a very small amount of radioactive material in the form of seeds or pellets under the skin where the cancer was removed. This is called brachytherapy or internal partial-breast irradiation.
Brachytherapy has the advantage of delivering very targeted radiation exactly where it's needed. Brachytherapy usually is given over 5 to 7 days, a shorter treatment time than external radiation, which usually takes 5 to 7 weeks. Still, current brachytherapy systems require a skilled and experienced medical team and available radioactive materials.
The Axxent system uses electricity and miniature x-ray tubes instead of radioactive materials as the source of radiation for treatment. A balloon-type device with very small cylinders is placed in the breast where the cancer used to be. The device is connected to equipment that supplies power to the miniature x-ray tubes. The cylinders carry the energy from the miniature x-ray tubes to the tissue. The device is removed after treatment is done. The women in this study received radiation treatment with the Axxent system twice a day for 5 days. All of the women in the study had had surgery to remove early-stage breast cancer.
Side effects of the Axxent system were similar to side effects seen with other brachytherapy techniques:
One woman developed a mild infection that was treated and went away. The balloon-type device ruptured in two cases during treatment but this didn't cause any problems.
It will be some time before doctors are confident this new brachytherapy technique is a good way to deliver internal partial-breast radiation therapy.
If radiation therapy is part of your treatment plan after surgery, you and your doctor will talk about which approach to radiation therapy makes the most sense for you. For some women, external radiation is the best approach. For others, internal partial-breast radiation therapy may be a good option. The Breastcancer.org Radiation Therapy section offers more information, including how radiation works to treat breast cancer, the different approaches to delivering radiation, and what to expect during and after treatment.
WASHINGTON, Sept. 10 (MedPage Today) -- An electronic brachytherapy device passed an initial clinical test, demonstrating the feasibility of intracavitary nonisotopic breast irradiation, according to preliminary results reported here.
Of 44 breast cancer patients treated thus far, the Axxent system successfully delivered the planned dose of x-ray energy in each of five fractions, Vivek K. Mehta, M.D., of Swedish Cancer Center in Seattle, said at the 2008 Breast Cancer Symposium.
Three grade-3 adverse events occurred -- one each of pain, blistering, and fatigue. All three events resolved uneventfully. The seven grade 2 toxicities -- three erythema, two pain, and one each for infection and breast firmness -- were mild and manageable.
"The early results suggest the equipment works as we expected, the safety is within that expected for patients with brachytherapy, and patient tolerance was very good," said Dr. Mehta.
Thus far, 25 patients have been followed for at least a month, and follow-up in all patients will continue for five years, he added.
For many patients with early-stage breast cancer, lumpectomy followed by radiation therapy is standard care. Fractionated external beam radiation requires six to seven weeks to complete.
Accelerated partial breast irradiation with conventional brachytherapy can substantially shorten treatment time, said Dr. Mehta. However, the therapy requires a skilled operator and a convenient, reliable source of isotopic material, which many centers cannot afford to maintain.
Electronic brachytherapy was designed to eliminate the need for isotopic radiation but maintain the shortened treatment duration afforded by accelerated partial breast irradiation, Dr. Mehta continued.
The Axxent system consists of a miniature x-ray tube contained within a multilumen catheter, a disposable balloon applicator, and a controller that powers the x-ray source. The system is housed in a self-contained, portable unit.
Treatment typically begins one to two weeks after surgery.
During a treatment session, the inflated balloon applicator is inserted into the closed lumpectomy cavity. The x-ray source delivers a radiation dose of 3.4 Gy per fraction, administered twice a day for five days.
Patients eligible for the ongoing study are 50 or older, have completely resected ductal carcinoma in situ (<2.0 cm) or invasive ductal carcinoma (<2.0 cm), and have negative surgical margins of at least 1 mm.
The primary endpoint of the study was successful delivery of the prescribed radiation treatment. The secondary endpoint was device-related adverse events.
The preliminary results showed that the system met the primary endpoint in the initial 44 patients, said Dr. Mehta. Treatment time averaged 8.35 minutes per session.
On two occasions, the balloon applicator ruptured between treatment sessions, but no complications resulted.
The study was funded by Xoft Inc., manufacturer of the Axxent system.
Several of the investigators in the study have served as consultants or advisors to Xoft and received research funding from the company. One was a Xoft employee.
Primary source: ASCO Breast Cancer Symposium 2008 Source reference: Mehta VK, et al "Early experience with an electronic brachytherapy technique for intracavitary accelerated partial breast irradiation" ASCO Breast 2008; Abstract 244.
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