Episode 29 Shownotes - Everything You Wanted to Know About Radiation and Breast Cancer

Well, hello friends! Hope you are well, and getting into the holiday spirit. I don’t know about you, but I have this thought I should be MORE organized this year, because I am not doing lots of the things I normally do, so WHY am I so much farther behind than normal in my holiday prep? Anyone else finding this? But, I am on a roll this week knocking out some podcasts to make sure I have great content for you awesome folks AND time for my awesome family. Now, if I can just find an Xbox, which I didn’t get and they are now all sold out. Hmmm.

Looking back, I realized it has been a while since my last solo science podcast, so am going to do one today. Today’s episode is all about what I know inside out and backwards – I could talk about this in my sleep – who knows, maybe I actually do! Today, we are going to talk about radiation and its use specifically in breast cancer. All the questions you had, answered without even having to ask! How awesome is that??? This is one of those talks – I am a doctor, but not your doctor. Practice patterns and radiation treatment regimens vary quite a bit around the US and throughout the world, so if what you got isn’t exactly what I am saying, please rest assured that there are many good ways to treat patients that are safe and effective. I am reviewing some of the most commonly used regimens in the US.

So first – let’s talk about what radiation is. Standard radiation is a type of high energy Xray. The most common type of radiation uses photons, which is a type of high energy electromagnetic energy in wave form. Photons have no mass. Two other types used in cancer treatment are lightweight particles with energy called electrons, and heavy particles with energy called Protons. If you remember back to high school science, electrons are part of the outer shell of an atom and protons are part of the nucleus of the atom.

All forms of radiation work by passing through your tissues and causing breaks in the DNA of cells. This DNA damage happens in both normal cells and cancer cells. Normal cells have DNA repair mechanisms that repair DNA if it is altered. In normal cells, if the DNA is damaged beyond repair, the cells will undergo programmed cell death – meaning the cell initiates the self-destruct feature, and kills itself off because it knows it is not right and is a danger to you. This is why there are short term side effects of radiation, like drops in blood counts, skin redness and fatigue. Tumor cells DO NOT have DNA repair mechanisms. That is what makes it a cancer cell – its DNA is messed up, and for some reason, it didn’t die off like it should, and your body did not recognize it as an abnormal cell and kill it off. So, without normal DNA repair mechanisms, when the radiation beam chops up the DNA of the tumor cells, the cells cannot divide (DNA has to replicate itself into 2 copies before the cell can divide), so when the cell tries to divide, it can’t and dies.

Radiation is done over multiple days or weeks to limit the damage to normal tissues – we know that if we give all of the radiation in one day, not only will it kill tumor cells, it will also kill many of the normal cells. Normal tissue sparing is enhanced by fractionating the treatment, or dividing it up over a number of days.

We will talk about radiation in localized, early stage breast cancer first. In node negative invasive breast cancer, after a lumpectomy, the standard of care is for all women under 70 with a good life expectancy to receive radiation. The reason for this is that there were trials done years ago that looked at lumpectomy alone or lumpectomy and radiation. The recurrence rates and survival were clearly better in the group with lumpectomy and radiation over the lumpectomy alone group. The recurrence rates and survival were just as good, or possibly slightly better than, mastectomy alone. For many years, the only way this was done was with whole breast radiation. This treated the entire breast, including all of the milk ducts. For more than 20 years, this was done over 25-35 treatments, given once a day. In the last 10 years, work was done in Canada, evaluating the results of shortening the duration of treatment to 16-20 treatments. They found equivalent survival and side effects, and so for many people, this is what is now being offered. Often, patients who have breast implants or expanders, or flap reconstructions are not eligible for this shorter treatment, but in the last 5 years, it has been shown to be safe and effective after chemotherapy and in patients with larger breasts, who were initially felt to be higher risk groups for quicker treatment. Also over the last 10 years, multiple studies have looked at radiating part of the breast, known as partial breast radiation, in highly selected groups with the very best prognosis. These studies have shown similar outcomes for whole breast RT and PBI in very good risk patients. This is differentially used across the US, due to many factors, but many places have increased their use of PBI in the setting of trying to minimize patient’s exposure risk during Covid 19.

Radiation is also used in more aggressive breast cancers. As above, if a patient keeps the breast, radiation needs to follow to at least the breast. Patients with positive lymph nodes may also need radiation to the nodal areas. Breast cancers most commonly spread to the lymph nodes in the low axilla or underarm first. From there, cancer cells can travel along the lymphatic chain to the higher axilla lymph nodes or the lymph nodes above the collar bone, known in medicine as the supraclavicular nodes. Sometimes we will also treat the internal mammary lymph nodes. These are nodes that are localized between the upper ribs adjacent to the sternum, or breast bone. These are more commonly involved if the tumor is in the inner half of the breast or if there is are many positive nodes in the underarm. If there is not clear involvement of the nodes at diagnosis, normally a sentinel lymph node dissection will be done. This takes either a blue dye, a radioactive tracer or both and injects them into the breast, and looks to see which lymph node the dye drains to first, and then that node is removed. If it is negative, then there is good data showing that the risk of finding other positive nodes is quite low. If the sentinel node is involved, many times (but not always!) additional nodes are removed. If there is clear involvement of the nodes at diagnosis, often a node dissection is done at surgery instead of a sentinel lymph node dissection. If nodes are found to be involved, radiation to the breast and nodes or chest wall and nodes may be recommended. All radiation oncologists agree that patients with 4 or more positive nodes at diagnosis require radiation, regardless of whether the patient had a lumpectomy or a mastectomy. In patients with 1-3 nodes, usually there is shared decision making with the patients. Lower risk patients with a small primary tumor in the breast and one small node after a mastectomy often will not be offered radiation. People with large primary tumors and 3 positive nodes usually will be offered radiation. Things that increase the risk of recurrence and push us to offer radiation include young age, lymphovascular space invasion, which is tumor extension into either the blood vessels or the small channels that lead to the lymph nodes, a large primary, especially if it is over 5 cm, higher number of nodes involved, extension out of the node into the fat of the underarm (also known as extracapsular extension). A high nodal ratio is concerning as well. This is when only a small number of nodes is removed and most of them are positive (ie. 3 nodes removed, and 2 positive) because this increases significantly the odds of additional involved nodes being left behind. Many of us also take into account higher risk histologies, like triple negative cancers, which are known to be more likely to recur both distantly and locally. Treatment of the internal mammary nodes is one of the most variable things in breast cancer treatment, with some sites treating them whenever they treat the other nodes on one end of the spectrum, to other sites that almost NEVER treat them. Hard to give you any clear guidance on this one – if you have questions, speak with your primary team.

A question I often get is why radiation might be recommended after mastectomy. Radiation is given in some patients after mastectomy if they are at high risk of local recurrence on the chest wall or in the nodes. Because the recurrence can be at both sites, we usually don’t radiate just the chest wall or just the nodes – usually we treat both. Treatment may be recommended due to nodal characteristics (more positive nodes = more risk of local recurrence) or due to primary tumor characteristics (very large primary or close margins are common ones). I want to explain why a tumor could grow back after mastectomy. Removing a breast from the chest wall muscles is similar to cleaning fat off of a cut of meat. We can get scrape and get most of the fat off of the steak, but even if we scrape a lot, we don’t get it all. Removing the breast removes the vast majority of breast cells, but some still remain on the surface of the pectoralis muscle, and can lead to recurrence based on many risk factors.

Radiation for breast cancer is usually started 4 -6 weeks after either the completion of surgery or if chemo is planned, 4-6 weeks after the last diagnosis of chemotherapy. We do give radiation at the same time as Herceptin, a drug used for her 2 positive patients that is given over a year total. We typically do not give radiation at the same time as AC or THP, due to a significant increase in side effects from treatment given together. Most commonly, chemotherapy is given before radiation, due to better tolerance of chemo pre radiation, and also to treat any cells that have spread systemically as quickly as possible. Radiation may be delayed if there are delays in healing after reconstruction, if breast expanders are being filled, or if there are other significant medical issues, but commonly our goal is to begin treatment by 12 weeks after surgery or chemo at the latest. Whether hormonal therapy starts during radiation or after varies by team and site in the country, but from my standpoint, I prefer to start hormonal therapy 2 weeks after radiation completes, so that if there are side effects of either the pill or the radiation, it is much easier to know which is causing the problems.

Radiation doses are chosen based on what we know we need to use kill breast cancer cells. In patients who receive whole breast radiation, many will get treatment to the whole breast first and then a boost at the end. A boost is additional treatment just focused on where the tumor was initially sitiing. The rest of the breast is finished, and the area of highest risk gets a bit more. It is actually a smaller field and less radiation than the initial phase. Some variation in dose may be present based on margins (meaning if there is suspicion that some cells might be left behind, a slightly higher boost dose might be used). Many people who have a mastectomy will NOT be treated with a boost, since the breast and area where the tumor was sitting are gone and stashed in the path lab somewhere.

One of the premises I was taught when I did a radiation rotation as a medical student is that if you aren’t hitting the right place you are giving the patient side effects without improving their cancer outcome. This means that it is really important that we are on target. The first step of setting up a radiation plan is with simulation. During this, we do (typically) a CT scan to map out where we want to treat, whether it is just where the tumor was sitting, the whole breast or the breast or chest wall and nodes. At the end of the planning scan, most sites mark a patient with tattoos, which are how we set things up each day. In the treatment room, there are lasers that line up on the marks. When all the tattoos and lasers are perfectly aligned, we know the patient is in the correct position and ready to go. Some sites take daily films to make sure treatment is aligned and others use what is called surface monitoring, where a program tracks the surface of the patient to make sure things are lined up as they should be. After the planning scan, a lot goes on in the background, where a team including the doctor, a physicist and a dosimetrist, create a plan to get the right treatment to the right areas, while avoiding what we don’t want to treat. On the first day, typically check films are obtained and reviewed by the doctor to confirm that treatment is lined up, and these are checked at least weekly to confirm we continue to be right on target.

A few great techniques are used to help to avoid things like the heart that we don’t want to treat. One way to avoid the heart, and also to improve the doses in patients with larger breasts is treating prone. What this means is that the patient is on their belly on a board with a hole on the side of the breast we want to treat. The breast falls into this hole, which pulls it away from the chest wall, ribs and heart. It also reduces skin folds in people with large breasts, which improves skin reaction from treatment. Another way we can avoid the heart is with what’s called breath hold treatment. This is done with the patient on their back. They take a deep breath, which pushes the heart farther back into the chest cavity and away from the radiation treatment. The patient holds their breath while treatment is given, and treatment is stopped intermittently for them to take a breath. These techniques, which years ago were only available at the universities, are more and more commonly available in the community.

Once treatment starts, it is most effective if it is given without breaks, so plan to be there for all of your planned dates, unless there is an emergency preventing your treatment. What this means is no vacation planned in the middle of your treatment! Occasionally a medical or weather emergency may come up, or a holiday may be in the middle of treatment. One day off during the treatment is not a significant problem! We just want to avoid longer delays, or many weeks with less than 5 treatments.

Radiation can cause both short and long term side effects. The side effects you experience will vary based on what is being treated, but most people will have some skin changes similar to a tan or sunburn. Some people may get blistering or skin breakdown. This is more common in people who had chemotherapy first, who have very large breasts or in patients being treated to larger fields including nodes. Many people have fatigue, and some people will have drops in blood counts (red count more often than white). Long term, the breast is like Forest Gump’s box of chocolates. You never know exactly what you will get. It often is thicker or firmer, smaller and darker. But, it can swell. Pigment can be lost in the nipple and areola, and in darker skin patients, in places with blistering and if there is color loss, usually this is permanent. Many people have chronic tenderness in the breast or chest wall. If the nodes are treated, there is an increased risk of lymphedema. There can be changes in the heart or lung on that side, based on the plan, and is more individualized. Finally, there is a risk of a second cancer from the radiation. This goes back to the mechanism of action. Remember we talked about breaks in the DNA of both tumor and normal cells? Very rarely, there can be a change in a normal cell and it doesn’t get fixed, the cell doesn’t go through its programmed death, and your body doesn’t identify it as cancer and 5-25 years later, a second cancer can arise. These occur in the area we treated (meaning, if you get a colon cancer after breast treatment, that is not from the radiation!). Often, these are a type of soft tissue sarcoma. What I tell patients is that new changes 5-25 years after treatment need to be brought to the attention of the surgeon or rad onc!

In terms of managing side effects, a few things stick out. Keeping the skin hydrated and supple is important. Any thick, nonfragranced cream is good. Massage helps to keep the skin thin and supple. Chest wall discomfort and stiffness can be improved by physical therapy or on your own by stretching, yoga and Pilates. Finally, if there is swelling of the arm or hand, known as lymphedema, physical therapy can help to treat this and reduce the effects, though this is a chronic condition, and will often require ongoing work.

Ok, my friends! Hopefully I have touched on all of the things you have wondered about in regards to radiation! I hope you are doing well as the covid numbers rise, being careful and staying safe in this final stretch before the vaccine is available. I’ll speak with you soon!