It’s flu season. A particularly bad one, too, according to nurses and medical professionals. If you’ve been following the news, you’ve likely heard of outbreaks throughout the country.
We all know the basic tips for staying healthy during the season: wash your hands, avoid sharing objects, get plenty of sleep, etc. These are all important. But what if you already have a weakened immune system? How will you get through flu season with breast cancer?
When you have or have had breast cancer, you need to know how it changes your ability to stay healthy. In many cases, treatment and not the cancer itself lowers your resistance. We discuss the effects of cancer and treatment on your immune system. We also talk about steps you can take to avoid getting sick when facing breast cancer and the flu.


breast cancer and the flu

How Breast Cancer Affects Your Immune System

Your immune system protects your body from viruses, fungi, bacteria, and other foreign invaders. It operates as a self-defense mechanism and keeps you from getting sick.
Dr. Gabriella D’andrea, a medical oncologist specializing in breast cancer at Memorial Sloan Kettering Cancer Center, says, “The immune system is a collection of organ systems, proteins and individual specific cells, which are divided into two main parts: the innate and the adaptive immune system. The evolutionary older innate immune system provides an immediate, general and nonspecific defense against pathogens. . . The adaptive immune system is a more specific, targeted, and complex system, which adapts and responds to specific threats or ‘antigens.’”

Why Doesn’t the Immune System Prevent Breast Cancer in the First Place?

To function properly, the immune system must distinguish foreign agents, such as viruses, from the body’s healthy tissue. This is how it targets and fights disease. Since breast cancer grows from your own tissue, the immune system does not detect it as a threat. Even though cancer cells are mutated, they are still your tissue, and the immune system does not respond.
Even though the immune system does not prevent cancer, it plays an important role in limiting breast cancer recurrence. It keeps metastasized tumor cells dormant. This prevents the cells from growing and lowers the risk that breast cancer will return. The adaptive immune system can even program the dormant cells to destroy themselves.
However, this requires a healthy and properly functioning immune system. When you have breast cancer, your immune system is weakened. This can be due to the cancer itself, but not unless it has reached later stages and has spread to the bone marrow. When cancer is in the bone marrow, it keeps the body from producing the blood cells needed to fight sickness.
“The immune system is typically unaffected by breast cancer in early stages of the disease. However, if the cancer is very advanced and extensively involves and replaces the bone marrow and lymph nodes, the immune system can be markedly impaired,” says Brian Lawenda, MD, a board-certified radiation oncologist who serves as the National Director of Integrative Oncology and Cancer Survivorship for 21st Century Oncology. Dr. Lawenda also serves as a Medical Director with Northwest Cancer Clinic, a Kennewick, Washington-based facility that is an affiliate of 21st Century Oncology. He incorporates integrative oncology in his practice to ensure that he treats patients as a whole in addition to treating their cancer.
For most people with breast cancer, the immune system suffers due to factors other than the cancer itself.
Dr. D’andrea explains: “Once a breast cancer has developed, it can subsequently continue to affect the immune system in many ways. The emotional burden of breast cancer, the medication and therapies used to treat cancer, and the presence of cancer cells themselves can alter the integrity of both the innate and adaptive immune systems. This may lead to further unchecked tumor growth.”

What Chemotherapy Does to the Immune System

Certain treatments for breast cancer decrease the number of white blood cells in your body. This means your immune system cannot operate at peak efficiency. Chemotherapy, while a very common option for treatment, is also the one most likely to weaken your immune system.
According to Dr. Lawenda, “Chemotherapy works, in most cases, by killing rapidly dividing cancer cells. Unfortunately, these drugs also kill other rapidly dividing cells such as hair follicle cells, intestinal mucosal cells, and bone marrow cells.”
When chemotherapy medicines are introduced to your body, they seek out and kill cells that divide quickly. Since these types of cells include breast cancer, chemotherapy medicines can effectively combat it. “Chemotherapy. . . primarily attacks cancer cells by altering their ability to grow or proliferate,” says Dr. D’andrea. But normal cells in your bone marrow, blood, hair, mouth, and other areas also divide quickly. Chemotherapy affects those cells, too.
Most of the time, your normal cells can repair themselves after chemotherapy treatment ends. Bone marrow has a harder time fixing damage done by chemotherapy, though. This directly impacts your immune system.
“If the bone marrow cells are significantly affected, the production of red blood cells, platelets, and white blood cells will drop, which can place the patients at higher risk of anemia, bleeding problems, and an impaired immune response to bacteria, viruses, yeasts, and parasites,” says Dr. Lawenda.
breast cancer and the flu

How Long is my Immune System Compromised After Chemotherapy?

To really understand how long it takes for your immune system to recover after chemotherapy, you should know some of the white blood cells found in your body.
First, we have neutrophils. These are the most common white cells in your blood and are responsible for preventing infections. If your neutrophil count gets too low, you develop neutropenia. This is a serious condition that can compromise your chemotherapy treatment or force your medical team to lower your chemotherapy dose.
Next, there’s B lymphocytes and T lymphocytes, also known as B cells and T cells, respectively. These cells regulate your immune response. They also attack harmful invaders found in your blood, such as bacteria.
Dr. Lawenda notes, “Typically, the immune system is suppressed for the length of time the chemotherapy drug stays in your body and for a few weeks after, until the bone marrow cells are able to recover.”
“Normal tissues and cells have a remarkable ability to recover,” says Dr. D’andrea. “Each cell has its own particular recovery time. For example, white blood cells, and skin cells, may not recover at the same rate.”
But this is not always the case. In one study, researchers found that the levels of T cells, B cells, and other natural killer cells dropped dramatically when people receive chemotherapy. However the levels of many of these cells returned to normal after a few months.
The cells levels that did not fully recover were the B cells and CD4 T cells, which are helper T cells. At nine months, these cells had only partially recovered to about 69 and 60 percent of their pre-chemo levels respectively. In smokers these cells were even more affected. Among these patients, cell levels only reached 51 percent of their pre-chemo levels after nine months.
Meanwhile, individual patients have reported varying amounts of time for when their immune system seems normal. For some, it took about 12 months to feel well. Others reported that their white blood cell counts went up and down for almost a year before stabilizing to their pre-chemo levels. Still others said that their levels returned to normal after a few months.
Some women have also reported that their white blood cell count is below normal after more than a year. Compared to before, these women get sick more often.
“…in some case[s],” Dr. Lawenda states, “the recovery can be significantly longer depending on the drugs used, the patient’s overall health, age, other medical conditions, and prior treatments they may have received.”
Dr D’andrea confirms, “Rate of recovery is also affected by age, other medical conditions, as well as repeated cycles of chemotherapy and combinations of treatments. Medications, emotional state, exercise, weight, nutritional factors and supplements can also affect immune function and recovery time.”

How Radiation Changes the Immune System


breast cancer and the flu

Radiation therapy and the immune system have a complicated relationship.
After radiation treatment, immune response kills surviving tumor cells more effectively. It even kills cancer outside of the radiation zone.
Despite this, radiation therapy also weakens the immune system.
Local radiation treats only the area where the breast cancer was found. For some, this type of therapy irritates the skin and leaves it open to bacteria and germs. You need to take extra care of your skin to prevent sickness when receiving local radiation.
“Radiation therapy does not significantly impair the immune system in most breast cancer patients when they undergo treatment directed to the breast,” Dr. Lawenda confirms. But there are still risks.
Dr. D’andrea further explains, “Radiation is a local therapy, which can damage DNA and affect the growth of both cancer cells and normal cells in the radiation field. Radiation alters the physical barrier which disrupts the integrity of the immune defense and can lead to infection.”
Local radiation therapy to the underarm area can also increase your risk of infection in the hand, arm, and upper body. You also increase your risk of lymphedema. This information is echoed by Dr. Lawenda, who says, “Radiation therapy, when directed at lymph nodes basins (such as the axilla, groin, pelvis) can impair lymphatic drainage through these areas, increasing the risk of a condition called ‘lymphedema.’ Tissues that are affected by lymphedema are at a greater risk of developing infections, as white blood cells are not as readily able to get into these tissues and mount an immune response.”
Any radiation directed at your bones decreases the amount of white blood cells your bone marrow can produce. This effect is similar to chemotherapy’s effect on the immune system. “…if the treatment needs to be directed to large areas of bone marrow (such as the spine or pelvis) due to metastatic disease, a decline in the white blood cell count can occur,” according to Dr. Lawenda. Further, high-dose radiation kills mature white cells that are already in your blood. So, your white blood cell count decreases and your body struggles to get white cell counts to normal.

What about low-dose radiation?

With low-dose radiation, the development, function, and growth of lymphocytes is harmed. This decreases how effective your immune system, leaving you open to several types of infection. This is the same problem as high-dose radiation therapy. It will just take a little bit longer for your white cell count to drop below normal levels.

How Long After Radiation Therapy Until my Immune System is Normal?

Many variables affect this. They include the pre-radiation condition of your immune system, the length and strength of your radiation therapy, and your lifestyle.
Unfortunately, many women notice a change in their immune system several years after their radiation treatment has ended. According to a study on the effects of local radiation, different types of lymphocytes do decrease after therapy. The amount of these lymphocytes remained lower than normal at 10 to 11 years post-treatment.
These lower levels were mostly caused by decreased levels in certain T cells, most notably the inducer and helper T cells. Suppressor T cells, a different T cell subset, did recover faster, but it still took about 5 to 6 years for these counts to return to normal.
Other studies have found similar results. Based on these previous studies, immune system recovery after radiation therapy is incomplete after 30 months.
Dr. Lawenda explains: “The recovery of the white blood cell count after radiation therapy to large areas of bone marrow is similar to that seen with chemotherapy, however tissues affected by lymphedema can be permanently at a greater risk for infections.”

Ways to Boost Your Immune System During Breast Cancer


breast cancer and the flu


It’s clear that breast cancer and treatment negatively affect your immune system. These effects can last for a long time. It’s important to be aware of this, but it doesn’t mean there is nothing you can do about it.
“People with breast cancer can ‘boost’ their immune system just like people without cancer. . .” advises Dr. D’andrea. “Physical and emotional well-being has been shown to be linked to better immune function. . . Vaccinations and health maintenance can reduce the risk of infections and help monitor for other illnesses which can subsequently weaken immunity.”
Here are some of the ways you can strengthen your immune system:
  • Sleep well. When you have breast cancer, getting a good night’s sleep is challenging. The side effects of treatment or menopause can wake you up frequently. Stress and worry may keep you from falling asleep. But you should aim to get at least seven hours or more of uninterrupted sleep every night. This prevents your immune system from being suppressed by sleep deprivation.


  • Eat healthy. Your immune system needs certain nutrients to operate properly. It’s important that you focus your diet around healthy foods by eating plenty of fruits and vegetables every day, such as cherries, celery, grapes, and artichokes. Only eat lean protein. Stock up on sources of whole-grain carbs and clear liquids. If you don’t feel like eating much during treatment, you can get calories from fruit juices or smoothies. To avoid nausea, try eating small amounts.


  • Reduce stress. While it’s normal to feel stressed when dealing with breast cancer, it isn’t healthy for you. Cortisol, adrenaline, and other stress hormones all suppress your immune system. They also lower your body’s ability to repair itself. Because of this, you need to practice relaxation daily. Yoga, meditation, and massage are all great for lowering stress. You can also try deep breathing or listening to music.


  • Fitness is hugely beneficial to immune system functioning. In most cases, it’s safe to exercise with breast cancer. Dr. Lawenda recommends a goal of 150 minutes of moderate-intensity physical activity a week.
    • Please note: if you experience extreme fatigue, have a low red blood cell count, or have poor muscle coordination, it may be best to limit or avoid physical activity. Always talk to your medical team before starting any exercise routine. They can let you know whether you’re healthy enough to exercise and give you advice about what exercises are best.

Preventing the Flu during Breast Cancer


breast cancer and the flu


People with breast cancer need to remain vigilant when safeguarding their health by following the below practices. However, they’ll benefit anyone looking to avoid the flu:
  • Regularly wash your hands using soap and water
  • Stay at least six feet away from people who are sick
  • Limit alcohol consumption
  • Avoid touching your eyes, nose, and mouth
  • Throw tissues away immediately after use
  • Stay away from small children who spend time in group settings like daycare
  • Drink plenty of fluids, eat healthy food, and get plenty of sleep
  • Sanitize your workspace
These tips are basic and familiar, but they’re crucial if your immune system is vulnerable. If you currently have or have had breast cancer, you must dedicate yourself to these everyday steps.
“If your white blood cell count is very low, you will be at an even greater risk of contracting infections, so be even more vigilant about hand washing and limiting your exposure to sick individuals,” explains Dr. Lawenda. “Wash your hands often, especially if you go out in public and you need to touch highly trafficked surfaces (such as counters and door handles). Wear a mask and limit your exposures as much as possible if you know you will be around other sick people.”

What else can you do?

“Make sure to ask your oncologist if you can get your annual flu vaccine,” says Dr. Lawenda. Dr. D’andrea also suggests the vaccine for Pneumococcal Pneumonia. If you do get vaccinated, make sure you get the flu shot over a nasal spray. Spray vaccines usually contain a weakened live virus. This virus can make you sick since your immune system will be weaker than a healthy individual’s.
Some people believe the flu shot will reduce how effective cancer treatment is. But this has not been shown. In most cases, it’s perfectly fine to get it during treatment. Still, you should check with your physician first.
By taking small and simple steps, you can actively protect your health this flu season. Take care of yourself. According to Dr. D’andrea, self-awareness is key. “Be good to your body, pay attention to signs and symptoms and seek medical attention if something is persistent and not right.”