How to Manage Diabetes and Cancer Treatment

This content originally appeared on Everyday Health. Republished with permission.

By Maggie Aime, MSN, RN

Medically Reviewed by Nimit Sudan, MD

If you’ve been diagnosed with cancer and you have diabetes, you should know that cancer treatments can have a strong effect on your blood sugar. It can be tricky to navigate the two conditions at the same time.

“People with diabetes undergoing cancer treatment may face specific challenges and potential complications due to the interaction between their diabetes and cancer therapies,” says Chevon Rariy, MD, an endocrinologist and the chief health officer of Oncology Care Partners.

About 1 in 6 people with cancer also have diabetes.^[1] Unfortunately, diabetes is associated with worse cancer outcomes, including more hospital stays, more infections, and a lower survival rate.^[2] This article will outline how these two conditions and their treatments interact and what you can expect.

Cancer Treatments Can Affect Blood Sugar Management

There are many different types of cancer treatment, and several of them are known to directly affect blood sugar levels.

Steroids

Steroids, which are often administered alongside chemotherapy, are a major cause of hyperglycemia (high blood sugar) during cancer treatment. Oncologists prescribe steroids to reduce chemotherapy side effects like fatigue and nausea, to protect a weakened immune system, or to treat the cancer itself.^[3]

Steroids, including corticosteroids and glucocorticoids, can directly spike blood sugar levels in people both with and without diabetes. This effect is so potent that in some cases steroids can even cause people to develop type 2 diabetes.^[4] If you’re using steroids, you may need to dramatically increase the amount of glucose-lowering medication that you use. Many patients are prescribed insulin to manage steroid-induced hyperglycemia and will need to measure their blood sugar more frequently.^[5]

Chemotherapy

Some chemotherapy medications can also cause hyperglycemia. Dr. Rariy says that this happens when chemo drugs lead to dehydration and electrolyte imbalances — too little or too much sodium, potassium, chloride, or calcium in the blood and other bodily fluids.^[6] Dehydration and electrolyte imbalances interfere with the body’s ability to regulate glucose levels, leading to blood sugar spikes.^[7]

Hyperglycemia can be a result of common side effects of chemotherapy such as nausea, vomiting, or diarrhea. If patients cannot eat or drink normally, it can make blood sugar management even more challenging, especially for those who use insulin every time they eat.

Rariy identifies the following chemotherapy drugs as risks for hyperglycemia:

• carboplatin (Paraplatin)
• cisplatin (Platinol)^[8]
• oxaliplatin (Eloxatin)^[9]
• paclitaxel (Taxol)^[10]

Targeted Therapy and Immunotherapy

Targeted therapy differs from chemotherapy. While chemotherapy attacks all cells that divide rapidly (including healthy ones), targeted therapy attacks only the cancer cells, preventing them from multiplying and spreading. Rariy says that certain targeted therapies, such as bortezomib (Velcade), used to treat multiple myeloma and certain lymphomas, can both lower and raise blood sugar levels.^[11]

Similarly, some immunotherapy drugs might impact blood glucose levels. These medications, including pembrolizumab (Keytruda) and nivolumab (Opdivo), are known to cause hyperglycemia in people who already have diabetes.^[12]

Cancer Treatment and Diabetes Complications

Cancer treatments can interact with other aspects of diabetes beyond blood sugar management.

Infections

“Diabetes can weaken the immune system, and certain cancer treatments, such as chemotherapy, also weaken the immune system,” says Rariy.

People with diabetes are already at higher risk for some common infections, like skin infections, fungal infections, and pneumonia.^[13] This effect can be magnified by cancer treatments like chemotherapy, which also sometimes weaken the immune system, leaving patients especially vulnerable to infections.^[14] In people with diabetes, infections can lead to dangerous consequences, including toe, foot, or leg amputation.

Radiation therapy can also increase the risk of infection. External beam radiation involves aiming tumor-destroying radiation beams at cancerous cells within the body. The beam passes through the skin, potentially changing or burning it. Weakening the skin barrier introduces a higher risk of skin ulcers from radiation, Rariy says. People with diabetes often have slow wound healing due to poor blood flow or nerve damage, which makes the skin even more likely to break down.^[15]

Cancer treatments can also worsen the long-term complications of diabetes in these ways:

• Both diabetes and certain cancer treatments can lead to nerve damage (neuropathy).^[16] These two factors, when combined, can result in increased neuropathy symptoms like pain, numbness, tingling, and can make daily activities challenging, Rariy says.
• Certain anticancer medications can also have damaging effects on the heart, known as cardiotoxicity.^[17] People with diabetes already carry an increased risk of cardiovascular disease. “The combination of both conditions may continue to elevate the risk of heart-related complications,” Rariy says.

Diabetes Can Interfere With Cancer Treatment

Your doctors may need to adjust your cancer treatment to account for your diabetes. “In some cases, healthcare providers might opt for alternative chemotherapy agents that have less impact on blood sugar levels or choose regimens that are less likely to exacerbate diabetes-related complications,” Rariy says.

Sometimes, your healthcare provider may spread out your cancer treatment to give your body extra time to recover, adds Rariy. Instead of administering one large dose of steroid, your oncologist may break it down into several small doses. Steroids can also be delivered slowly over an extended time via an intravenous (IV) tube. This gradual absorption reduces the risk of increasing your blood glucose.^[18]

Blood sugar management concerns could necessitate delays in your cancer treatment. For example, if you experience persistent high blood sugar levels while undergoing cancer treatment, your oncologist may pause treatment until your blood glucose is better controlled, Rariy says. This could help avoid further complications, but your healthcare team will have to strike a balance so that there isn’t a negative impact on your cancer prognosis.

Your healthcare providers should utilize a team-based approach to ensure that cancer and diabetes-related concerns are handled right away to avoid complications, says Rariy. Advice from multiple experts, such as oncologists, endocrinologists, nurses, and other healthcare professionals, is often needed.

How to Manage Your Diabetes During Cancer Treatment

Your diabetes treatments may need adjustments during cancer treatment. In particular, you may need new medications to help control your blood sugar if your cancer treatment is leading to hyperglycemia, possibly including insulin injections, Rariy says.

Working together with your healthcare providers is important when dealing with diabetes during cancer treatment. Good diabetes management can help prevent complications and interruptions in your treatment. Here are a few things to be mindful of.

• Schedule a visit with your endocrinologist. Chhaya Makhija, MD, an endocrinologist in private practice in California, says to see your endocrinologist even before starting cancer treatment. Your endocrinologist can help adjust your diabetes medications or insulin doses to ensure your blood sugar stays well-controlled during cancer treatment.
• Keep your oncology team updated. Make sure your oncology care team is fully aware of all the diabetes medications you take. Tell them if your diabetes medications change or if you notice any changes in your symptoms.
• Keep a close watch on your blood sugar. Your care team may ask you to monitor your blood sugar levels more closely, says Dr. Makhija. Ask how often you should check your blood sugar throughout cancer treatment. Keep a record of your blood sugar levels and notify your healthcare providers about any unusual high or low readings.
• Watch out for diabetes warning signs. Watch for cues that your diabetes management needs attention. These include unexpected blood glucose spikes, increased nerve pain or numbness, blurry vision, feeling extremely tired or thirsty, and frequent urination. Notify your oncologist or endocrinologist right away if you notice these symptoms.
• Eat healthy foods. Makhija recommends working with an oncology dietitian and diabetes educator to help guide you. Your oncologist or nurse can refer you to a dietitian. “Avoid processed foods and high-fat meals,” Makhija recommends. Ask about nutrition shakes and homemade plant-based recipes that are lower in sugar and simple carbohydrates and higher in other nutrients and protein, she adds.
• Stay active and prioritize healthy sleep. Don’t forget about the importance of staying active and sleeping well, Makhija says. “[These] help with both glucose control and side effects of cancer therapy,” she adds. Engage in physical activity as tolerated.
• Practice stress management. Stress, which spikes the levels of cortisol and other glucose-raising hormones, can drive high blood sugar. It may not be easy to stay relaxed during cancer treatment, but it’s worth trying. Rariy recommends practicing self-care and making your well-being a priority.

The Takeaway

• Some cancer treatments, including chemotherapy and steroid treatments, can cause high blood sugar levels.
• If you have diabetes and cancer, your care team may have to slow or alter your cancer treatment in order to reduce the risk of diabetes management issues.
• Diabetes may aggravate some cancer treatment side effects, such as the risk of infections. Others, such as dehydration, could make it more difficult to control your blood sugar.
• Your diabetes management may become especially complex during cancer treatment, requiring new medications and extra glucose monitoring. Navigating the two conditions simultaneously requires the cooperation of a team of healthcare professionals.

Resources We Trust

• Mayo Clinic: Sugar’s Role in Cancer
• Centers for Disease Control and Prevention: I Have Diabetes and Cancer. What Can I Eat?
• MD Anderson Cancer Center: Diabetes and Cancer: What You Should Know
• Leukemia and Lymphoma Society: I Have Cancer and High Blood Sugar: What Do I Do?
• American Diabetes Association: Know the Diabetes-Cancer Link

Editorial Sources and Fact-Checking