By Elisa Krill-Jackson, M.D.
Board-certified hematologist and oncologist
Sylvester Comprehensive Cancer Center
The biggest question I get from my patients is, "When is my immune system going to recover from the chemotherapy?" In fact, I've had patients who had chemo 15 years ago email me and ask me, "Is my immune system normal?" What I have to tell them, for the most part, is, "Yes. It should be normal at this point." But it does take a while for our immune systems to get back to normal.
Immune system cells
Neutrophils are the white cells that fight bacterial infections, and these recover within a few weeks. These are the cells that we check every time you get chemotherapy to make sure they are high enough for you to receive treatment that day. They recover very quickly.
However, our lymphocytes are cells that can take a little bit longer to recover. B cells are cells that make antibodies against bacteria and viruses. And, CD4 T cells also protect against viruses and also fungal infections. These can take a long time to recover.
The image above shows levels of immune cells in your blood. If you look at graph A on the top, what you can see here in this first bar is where patient's B cells were prior to chemotherapy. Two weeks after they finished chemotherapy, you can see their B cells are quite low. But at three months, they are increasing, and at six months they've increased even more. At nine months, they're almost back to the normal level, on average. So are the CD4 cells.
Chemotherapy and COVID-19
Before coronavirus, we really didn't see patients getting more severe infections in the months after chemotherapy. However, we don't know if patients might be more at risk for severe COVID-19 infections in the months after chemotherapy. So I'm cautioning my patients that they may still be somewhat immunosuppressed for several months after their chemotherapy. So they should really be social isolating, washing their hands, avoiding situations with large crowds, and avoiding people who are sick.
There is also a very interesting study about cigarette use and immune system recovery after chemotherapy. It found that patients that smoke are much slower to recover their B cells and T cells. In the study, smokers and nonsmokers have about the same number of B cells on average before chemotherapy, and about the same two weeks after chemotherapy. But, three, six, and nine months after chemotherapy, smokers have a much, much more delayed recovery of their B cells than the nonsmokers do. This is a really good reason to quit smoking even if you're on chemotherapy. We also know that smokers do much worse if they get COVID, probably due to lung damage from cigarettes. If you are a smoker, hopefully, this data gives you one more reason to quit.
It all comes down to a weakened immune response, which can be caused by cancer treatment or cancer itself. Your immune system, unfortunately, isn’t as strong as it could be, so you have to take extra precautions to protect yourself from coming into contact with the virus. Read more.