You may worry, "What happens if I lose lymph nodes to surgery, or my white count drops dramatically because of chemotherapy? Is my immune system weakened, and will I become vulnerable again to cancer and infection?"
Fortunately, your immune system is very resilient and flexible. Various parts can switch roles and fill in for each other. You also have a considerable reserve or surplus of immune cells and tissues. If some lymph nodes are removed, others take up the load, handling the circulation of lymph fluids and filtering out cancer cells, bacteria, and other unwanted elements. Because you have so many more white blood cells than your body requires, most of the time a reduced number of white blood cells won't put you in any serious danger. New lymphocytes and macrophages can be mobilized in a matter of minutes. However, it is important to be aware of your blood counts.
Blood counts are used to determine any possible damage chemotherapy or radiation has caused to your immune system. It takes just a few drops of blood to identify the number of all types of blood cells in your system. How much your white blood cell count declines depends on you as an individual, your general health, your treatment, the dose and interval between treatment cycles, and the total dose you've received over time.
Chemotherapy and blood counts
Chemotherapy drugs can lower blood counts significantly because they reach all sites of blood cell production. Immune cells in particular are very sensitive to the effects of chemotherapy. Really low blood count levels are usually temporary, but may last longer if you have received regular doses of chemotherapy over an extended period of time, or after the very high doses of chemotherapy that precede bone marrow transplantation.
When your blood counts are very low, your thymus, spleen, bone marrow, and lymph nodes respond by calling on their reserves and revving up the production of more white cells. While your immune cell counts are at their lowest, you run an increased risk of developing an infection. As tempting as it is to skimp on the dose to avoid some of the side effects, it's better to get the doses you need get the full cancer-fighting benefits of chemotherapy. What you CAN do is to step up the medications and nutritional measures that will support you and ease your way through.
When immune cell counts fall too low
When your immune cell counts fall below a critical level — to 1,500 or fewer frontline cells (called neutrophils) — you are more vulnerable to infection and illness. If your counts drop to these levels, your doctor is likely to begin immune support treatment before an infection has a chance to start. This includes antibiotics if there's any sign of infection. Your oncologist may also delay your next chemotherapy treatment and, if necessary, give you growth factors to speed up your production of immune cells. You might wonder if immune cell transfusion is possible to increase your counts (just like a blood transfusion for some kinds of anemia). But this type of transfusion is rarely done because it can lead to complications.
Once your immune cell counts rise above a critical level, your system is sufficiently armed to fight most infections. Chemotherapy can usually resume when the count is between 2,000 and 2,500. The next dose of chemotherapy given will depend on what your immune system can tolerate. Your doctor will work closely with you to manage all these issues.
Radiation and blood counts
Radiation to the breast area alone produces a minimal drop in white blood cells. But when the lymph nodes are also irradiated, the decline is somewhat steeper. Radiation to bones for metastatic disease can also cause low counts, especially if the vertebrae, pelvic bones, and leg bones are treated, because new blood cells are produced in the marrow of these bones.