OPTIONS IN BREAST CANCER RADIATION THERAPY

By Chris Hagness, Ph.D

Radiation therapy
If you’ve talked with a radiation oncologist, then you’ve already heard about the benefits of radiation treatments for your particular type of breast cancer. The standard of care for radiation therapy of breast cancer is whole breast external beam radiation. In this type of radiation therapy, high-energy xrays produced in a machine pass through the breast to deliver the radiation. Whole breast radiation therapy is often given after a lumpectomy or mastectomy (also called chest wall irradiation). This type of treatment is given 5 days a week for up to 7 weeks. The most common side effect of this treatment is skin redness.

Breast brachytherapy
Brachytherapy is a method of delivering radiation using a small radioactive source. The source is placed inside the area to be treated. For breast brachytherapy, the source has to be placed inside the breast tissue where the tumor was removed. This requires teamwork between your surgeon and your radiation oncologist. The radiation is delivered from inside the breast and targeted to the area where the cancer was. The amount (dose) of radiation given is less than conventional therapy because it is given over a shorter time. Breast brachytherapy is typically given twice per day for 5 days. The side effects of this type of treatment are skin redness, bruising, and breast pain – common side effects of breast surgery.

Advantages and disadvantages
Neither type of treatment makes the patient radioactive after the treatment is finished. The obvious advantage of brachytherapy is the shorter treatment time. But brachytherapy and conventional radiation therapy, which is still the standard of care, are fundamentally different. This difference may or may not be given its due consideration when discussing your treatment options with your physician. Conventional radiation therapy irradiates the whole breast, giving the same radiation dose to all of the breast tissue. Brachytherapy irradiates only a small area of the breast, around where the tumor was located before it was surgically removed. This is called partial breast irradiation.

Partial breast irradiation
The supposed benefit of partial breast irradiation is that it limits the amount of radiation to healthy breast tissue, thereby reducing the potential for side effects. This is a concept that is applied to radiation treatments given in other parts of the body, where there are nearby organs such as the liver or kidneys which may suffer serious side effects. Not all physicians believe this is a wise approach to the treatment of breast cancer, however. 

​There are two main reasons why partial breast irradiation remains controversial:
1) The breast is not an organ. An organ has a membrane that encapsulates the tissue. Breast tissue is sandwiched between the muscular chest wall and the skin, and is permeated by blood vessels, lymphatic ducts, and mammary glands. Cancer that arises in breast tissue has no physical membrane to prevent its spread to nearby breast tissue, and the likelihood of it spreading is high because of the vessels and ducts.
2) There are no nearby organs that require protecting from the radiation. In general, the only tissue that receives more radiation with conventional therapy is the breast being treated and the skin around it. The only side effect that can be reduced using partial breast irradiation is skin reaction, which is usually easily manageable and disappears sometime after the treatments are finished.

In the mind of a physician, it would be bad for a patient to suffer side effects during treatment. However, it may be worse for a patient to go through a partial breast treatment and later have a recurrence of breast cancer outside the treated area. Because it has been used once already, it may be impossible to use radiation again to treat the recurrence. That physician has spared the breast from radiation only to lose it to surgical resection, or may have allowed an undetected area of cancer in that breast to go untreated, grow, and possibly metastasize. Whole breast irradiation will kill cancer cells in the entire breast, including those away from the area that was removed surgically, and is a more cautious choice of treatment.

Clinical studies
There is now data available from studies indicating that partial breast irradiation can be used safely and reproducibly. Reported local recurrence rates are low and comparable to conventional whole breast radiation therapy. It should be noted that patients enrolled in these studies were carefully selected to minimize the risk of local recurrence. Appropriate patient selection is essential to successfully treating patients with partial breast irradiation as an alternative to whole breast radiation therapy. Also, the data from these studies has only been collected for five years or less. Because breast cancer recurrence may happen up to 10 years or more after treatment, the final numbers have yet to be reported and may yet change.

MammoSite balloon catheter brachytherapy
MammoSite is one method of breast brachytherapy. After the surgeon removes your tumor, an uninflated balloon is gently placed inside the tumor cavity through a small incision. A catheter will remain outside of your breast which allows the radiation source to be inserted into the balloon. The MammoSite balloon can be placed either during your lumpectomy surgery or up to 10 weeks later in a separate procedure. Once in place, the balloon is inflated with fluid to fit snugly into the tumor cavity. The balloon remains inflated for the entire time you are receiving radiation therapy. A tiny radioactive source will then travel from the machine, through the catheter, and into the inflated balloon inside your breast. The source will remain in the balloon for about 10 minutes while it delivers radiation. Once you have received the prescribed dose of radiation, the source is retracted back into the machine. Usually on the same day as your last radiation treatment, the balloon will be deflated and removed. Is it for me? Anyone can receive the standard of care, whole breast radiation therapy. For breast brachytherapy, appropriate patients are over 45 years of age and have early-stage breast cancer with tumors greater than 2 cm in size, invasive ductal type, negative surgical margins, and negative lymph node status. Radiation therapy with brachytherapy is an accepted treatment for breast cancer and is covered by most insurers. Specific coverage for MammoSite or other treatment options will depend on your individual health plan. More information on MammoSite can be found on their website at www.mammosite.com. 

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