The following questions are taken from an interview with Dr. De Los Santos. While many of these points can apply to other regions of the body, these questions focus on radiation treatment for breast cancer.
What is radiation therapy?
Radiation is very high-powered x-rays, used for treatment purposes. The radiation that you receive in radiation oncology is at a much higher power than you would receive for mammograms or any other diagnostic radiology studies.
Why is radiation used for the treatment of cancer?
Radiation therapy treats cancer in a variety of ways. For breast cancer, radiation is typically used to reduce the local occurrence after breast surgery. The type of surgical procedure used may alter the way the radiation is delivered. For example, when a patient has had a mastectomy, where the breast is removed, radiation would be used to treat the chest wall, as well as some of the lymph node bearing regions above the collarbone and underneath the arm. For someone who has had a lumpectomy, which is removing a lump from the breast, only the breast and the cavity where the cancer used to be located would be treated. The focus of where the radiation needs to be delivered can change. In both applications, radiation therapy has been shown to reduce recurrence. For those who have had a mastectomy, some studies show that radiation helps improve survival.
How does it do that? Does it select and kill only the cancer cells?
Radiation treatment acts by killing the DNA within the cells. Radiation cannot actually choose between a cancer cell and a normal cell. The current clinical thinking is that the cancer cell (being deformed as it is) does not have the capacity to repair the damaged DNA after an exposure to radiation, whereas the normal cell is able to repair. That is why radiation therapy is given in small doses over multiple days to preferentially spare the normal cells, allowing them time to heal; while the cancer cells, which have faulty repair mechanisms, will subsequently die.
Can you talk a little bit about the dosing of the radiation and typical dosing that someone would receive?
Radiation treatment to the chest wall after someone has had a mastectomy or lumpectomy typically will run 25 to 28 treatments encompassing the larger field, which would include the whole surgical area. After the 25 to 28 treatments, usually a boost is delivered. This does not mean the fraction size or the treatment size is larger, it just means we are focusing on the area where most of the microscopic tumor cells might remain. These treatments would usually be additional 5 to 8 treatments, focusing either on a mastectomy scar (for someone who has had the breast removed) or focusing on the lumpectomy cavity.
Can you mention how radiation is measured and how the appropriate amount is determined? Is it rads these days?
Right now, we are using a term called “a grey”, which is a unit of any absorbed dose. A way to think of it is “time under the radiation beam”, but it really is more complicated than that.
What would be the typical maximum dosage someone would receive in a treatment?
Typically, per treatment, you would receive 1.8 to 2 grey. The total dosage for the chest wall or for the intact breast, would be 45 to 50.4 grey. The boost can range anywhere from 10 to 20 grey, and would depend upon other factors which are related to the tumor biopsy, or the surgery that was performed.
What are the side effects of radiation?
Side effects of radiation therapy (during treatment) range from fatigue, skin redness, and occasionally, skin blisters. Some areas of the skin are more sensitive than others. Many patients think that if they burn in the sun, they will be more likely to have skin effects during radiation therapy. Clinically we are not finding this to be true. I have had patients who are fair skinned, blue-eyed or green-eyed, sail through radiation with no trouble even though in the sun they burn easily. Then there is the patient with an olive complexion who has no trouble lying out in the sun, but can have trouble with radiation, and vice-versa. Other side effects of radiation therapy (for example for breast cancer) may include swelling both of the breast(s) and chest wall, as well as the arm region. During the treatment, that swelling may actually go down. It is much like having sunburn, you get kind of “puffy” after having a sunburn.
What about diarrhea?
There should not be anydiarrhea, or nausea. You may have a little pain from the skin effects, but that is about it.
Are there systemic effects?
There is some fatigue, but it is not enough that you would be unable to carry on your daily routine. Some women continue to work during treatment, but notice it feels as if there is an anchor dragging behind them. Radiation therapy to the chest area can cause lung inflammation. There is controversy as to whether radiation therapy to the chest adds to your risk of heart disease if you are treated on the left side, where your heart normally sits. Radiation can slow down the bone turnover within the ribs and you might develop a more fragile ribcage within the next few months after finishing radiation. You should be careful to avoid trauma or injury to the chest/ribs on the side of the radiation.
That would be for any bone within the radiation field?
Yes, within the radiation field only, wherever we aim the beam.
What are long-term effects?
There may be some long-term skin changes. Many women heal well and you cannot tell that they had had radiation treatment, but some women do experience a change in skin color, either a darkening of the skin or a lightening of the skin. Sometimes, people will develop spider veins.
The other potential side effect is that radiation therapy can add to the risk of lymphedema. Lymphedema risk also depends on the type of surgery. A full dissection, meaning removal of as many lymph nodes as possible, may put this patient at higher risk for developing lymphedema than the patient with a sentinel node biopsy in which one to five lymph nodes are removed.
Can you speak about why the radiation can increase the risk of lymphedema?
In breast cancer, we know that the surgery has removed some of those lymph node areas that were serving as a primary drainage of fluids and proteins from the arm. There is some trauma from that and you may develop some scar tissue in that region. Radiation therapy can add to the scar tissue formation, not that your scars will be over the arm area, but rather underneath the arm. You may have some firmness of that tissue, and your lymphatic system may not be able to function quite as well because of the toughening of that tissue.
What are the things that are done to try to prevent the occurrence of lymphedema with radiation?
The primary goal of radiation therapy is to make sure that the carcinoma (cancer) does not come back. The worse possible outcome is treatment failure. Radiation fields and ports are determined by the location of the disease. If you need treatment in the axilla because there were several positive lymph nodes, or, if you need radiation therapy above the collarbone because there might be microscopic disease there, we are going to go ahead and treat those areas. There is nothing that we can do to avoid individual lymph nodes and still treat the cancer that might exist in the lymph nodes. Because of this, we end up needing to treat in areas where we know there is a risk for increasing the chance of developing lymphedema.
The biggest thing that we try to do as clinicians is teaching about the prevention (risk reduction practices) of lymphedema as well as monitor for swelling during the treatment and follow up.
Is there a maximum dose?
The maximum dose of radiation therapy is tailored to what the normal tissue can tolerate. The administration of radiation treatments in terms of dosing is gradually evolving; we now have newer techniques, and longer patient follow up. In general, most patients will not be treated above 60 – 66 grey. This is partially due to the skin erythema (redness) and skin fibrosis, but it is also limited by concerns regarding other structures, for example, structures like the brachial plexus where you do not want to injure the nerve. However, clinical practice is changing; some patients will come back with recurrent disease of the chest wall and if there is a long enough span of time between the first therapy and this occurrence, we can go head and treat them; so in some cases radiation doses may be as high as 100 – 110 grey.
Is there any advice that you give to patients who had radiation treatment for breast cancer to help them prevent complications?
We recommend surveillance (close watching and communication between the patient and health care practitioner). The patient should be able to tell you “Hey, my ring is fitting snugger”, so we can begin implementing intervention sooner. We do tell patients to limit the amount of weight lifted by the affected arm to no more than twenty pounds. We also tell patients to avoid trauma to that area – if they ever have give blood or have blood drawn for labs, to have that done on the opposite arm. Blood pressure should be taken on the opposite arm to limit any trauma, which might increase the risk for lymphedema. We also tell them their risk for lymphedema never goes away, and they can be fine for years and years and all of a sudden, they may develop lymphedema. Therefore, patients have to be diligent.
That being said, there are many studies that are beginning to look at weight training and lymphedema. Studies have shown that weight training can help as far as the survivor’s perception of her self and certainly, it is helpful to exercise and stay active for body weight management and over all health. I think keeping the arm toned and active is a good thing. These studies have shown that weight training does not increase the risk of lymphedema. The largest study that came out in 2006 evaluated a variety of weights; unfortunately this study did not go into a lot of specifics, but sounded like the subjects began with very small weights of one-half pound and then worked up gradually two or three times a week. We tell patients to limit the pounds lifted and to wear a compressive sleeve while they are doing their activities; they can stay active and do light weights in order to keep that arm healthy.
ther things contribute to lymphedema --- obesity, diabetes, defects in vasculature, and smoking probably causes problems, but these things are very difficult to test.
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