If you’re getting chemotherapy, you’ll become accustomed to having regular lab work done before each chemo session. This is to make sure you’re healthy enough to receive your treatment that week.
In this post, you’ll learn how to understand and interpret your basic lab results. Let’s get started!
Most centers run a complete blood count (CBC), complete metabolic panel (CMP) and tumor marker tests, such as CEA and CA 19-9.
The complete blood count measures your white blood cell, red blood cell and platelet counts. Since chemotherapy can lower your blood counts, it’s important to make sure they’re high enough to receive chemo safely.
If your counts are too low, your oncologist may delay your chemo treatment to give them a chance to recover. If your white blood cell counts are consistently low, your oncologist might recommend an injection such as Neupogen or Neulasta to help prevent treatment delays. If your red blood cell counts dip too low, your oncologist might recommend a blood transfusion.
The complete metabolic panel checks your kidney and liver function. Your kidneys and liver need to be working properly in order to process the chemo drugs. Liver enzymes can often become elevated when on chemo drugs, as your liver is working extra hard to process them.
If your numbers are too high, or too low, your oncologist may need to delay chemo in order to give your organs a chance to recover. If kidney and liver function is a consistent problem, your oncologist may consider various interventions to prevent treatment delays.
CEA — and less commonly, CA 19-9 — are blood markers that can become elevated in people with colorectal cancer. These tumor markers are not a good predictor for everyone, as some stage IV patients have CEA and CA 19-9 levels within normal range — despite having widespread disease! However, for many patients they can be a good predictor of whether cancer is progressing or not — and how you are responding to treatment.
It’s also important to remember that tumor markers can become elevated for a variety of other reasons, particularly related to inflammation. For example, several COLONTOWN Community members have reported receiving elevated CEA results shortly after a COVID vaccine. For this reason, it’s very important to have your oncologist help you interpret these results in context with other surveillance methods you may be using.
Most infusion centers require these tests prior to every chemo infusion. For most chemo regimens, that means once every two weeks (but in some cases, like the Capox regimen, would be every 3 weeks). Some oncologists will order the tumor marker tests less frequently, such as once a month — or not at all, if they’re not good predictors for you.
You will usually be given an appointment to come in an hour or so before your infusion starts, or sometimes on the day before. A nurse will access your port or PICC line, and draw vials of blood. Then, the nurse will leave the needle in your port and apply a dressing. If you don’t have a port or PICC line, they will draw blood from a vein in your arm. Now you’re ready to receive chemotherapy!
The image below shows how your port is accessed for routine blood draws:
After your blood draw, the results will take about an hour to come back. Before starting your infusion, your oncologist will check your results to make sure it’s safe for you to get your treatment.
To make this a bit easier to understand, below is a sample copy of what your routine labs might look like. Let’s call this patient Sara.
These are screenshots from an online portal. If your cancer center has a portal, it’s a great idea to set up an account. It makes it much easier to access your medical records, and keeps them organized in one place. If your cancer center doesn’t have an online portal, remember to get printed copies of all of your tests and scans for your records. You never know when you may need them later on while searching for a second opinion!
Now, let’s get into the details.
The first four images show the CBC, which are blood cell counts. Sara’s numbers are at the top, and the normal values (called the reference range) are at the bottom. Remember, this reference range is for the general population — not specifically for people with cancer or people going through treatment.
Your oncologist will use different parameters for your results, based on your personal situation. If you have any concerns about your test results, it’s a good idea to speak to your oncologist.
WBC: This stands for white blood cell count. Sara’s WBC count is elevated, probably due to a Neulasta injection. For patients who don’t receive these injections, WBC counts are often lower. If your levels drop too low, it can compromise your body’s ability to fight off infection — so chemo might be delayed to keep you safe. There are several conditions that increase WBC counts in people who don’t have cancer and who are not undergoing chemotherapy — but we won’t cover that here.
RBC: This stands for red blood cell count. Sara’s RBC is a little low, which is very common for patients undergoing chemotherapy. At this level, most patients should be able to receive chemo safely, but it’s always important to follow your care team instructions. Several conditions can affect RBC counts in the general population, but are not discussed here.
HGB: This stands for hemoglobin. Sara’s hemoglobin is also low, which is very common during chemo. At this level, most patients should be able to receive chemo safely, but each individual case is different.
HCT: This stands for hematocrit. Sara’s levels are low, which is a common side effect of chemo. At this level, most patients should be able to receive chemo safely, but each individual case is different.
Neutrophils: Sara’s neutrophil levels are elevated, probably due to Neulasta injections. If these levels get too low, your care team might delay chemo to give your body more time to recover.
Lymphocytes: Sara’s lymphocytes are within normal range. If they get too low, chemo might have to be delayed.
The following four images show Sara’s complete metabolic panel (CMP) — which gives your oncologist information about your kidney and liver function.
Sodium, potassium and chloride: These are key electrolytes. If a patient’s levels get too low while undergoing chemotherapy, it may indicate dehydration — usually from vomiting or diarrhea. Your team will probably recommend supplemental fluids, at least for a little while, to bring your levels back up. For patients with ileostomies, it’s very important to keep a close eye on these numbers, as you’re more prone to getting dehydrated.
AST, ALT, alkaline phosphatase: These are liver enzymes that often become elevated with chemotherapy. This is because your liver is working overtime to process the chemo drugs! Sara has a slightly elevated ALT and alkaline phosphotase, but she should still be able to receive chemo at these levels. If your numbers get too high, your team may need to delay chemo to give your liver more time to recover. Bilirubin is another marker that indicates normal liver function, and can increase in cancer patients on chemo.
CEA: The last result on the list is carcinoembryonic antigen (CEA), a tumor marker. Sara’s is slightly elevated based on the normal range. However, this result needs to be interpreted by an oncologist in the context of Sara’s history, diagnosis, and other surveillance tools such as scans and liquid biopsies.
Your team will be regularly checking your blood work to make sure it’s safe for you to receive chemo. They will be looking very closely at your white blood count, red blood count, hemoglobin, hematocrit, platelet, neutrophil, and lymphocyte counts. They will also check your liver and kidney function. If you are receiving Avastin, it can affect kidney function — so you may also be required to take a urine test to ensure there’s no protein in your urine and your kidneys are working well.
The exact cutoff levels can vary slightly based on your infusion center, treatment protocol and specific situation. However, if your blood counts are too low, liver enzymes are too high, or your kidney function is off, your team may delay your treatment.
This can be a huge source of anxiety for patients, but know that an occasional delay in treatment is unlikely to significantly affect your overall outcome or prognosis. If you have questions about your cancer center’s policy, talk to your oncologist. If delays become a consistent problem, there are some things your team can recommend to help prevent this!
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