Management of Comorbid Diabetes and Cancer

July 1, 2007

Diabetes mellitus is a frequent comorbidity of cancer patients. The growing epidemic of diabetes is anticipated to have tremendous impact on health care. Diabetes may negatively impact both cancer risk and outcomes of treatment. Oncology nurses are ideally positioned to identify patients at risk for complications that arise from cancer treatment in the setting of pre-existing diabetes. Additionally, oncology nurses may be the first to identify underlying hyperglycemia/hidden diabetes in a patient undergoing cancer treatment. Strategies for assessment and treatment will be discussed, along with specific strategies for managing hyperglycemia, potential renal toxicity, and peripheral neuropathy. Guidelines for aggressive treatment of hyperglycemia to minimize risks of complications will be reviewed. The role of interdisciplinary care, utilizing current evidence, is crucial to supporting patients and their families as they manage the challenges of facing two life-limiting diseases. Whole-person assessment and individualized treatment plans are key to maximizing quality of life for patients with cancer and diabetes.

Well-controlled diabetes thrives on consistency—consistent food intake, activity level, and lifestyle, day after day, year after year. This, of course, presents one of the greatest challenges to patients living with diabetes. Cancer and cancer treatments are notorious for wreaking havoc and creating instability in body and mind. Clinically, either one of these diagnoses is a challenge to both patient and clinician. Together, they present a formidable obstacle requiring the collaboration of an interdisciplinary team to ensure good outcomes. This challenge is further complicated by a lack of research to guide clinical decision-making in managing diabetes while simultaneously treating cancer.

Singer provides a comprehensive overview of some of the most common problems confronting nurses caring for this patient population. The article begins with an up-to-date overview of the epidemiology and pathophysiology of diabetes, followed by a summary of some of the (few) studies of cancer and comorbid diabetes. As with other comorbidities and diabetes, it is not surprising that cancer patients with diabetes have a statistically significant higher risk of cancer recurrence and mortality. What is frustrating to those of us practicing within the clinical sphere is the lack of knowledge about why this is so.


While we await the conduction and publication of such studies, we are left to assume and/or hope that glycemic control can affect cancer outcomes as it does with other comorbidities such as cardiovascular disease. Currently, there is a difference of opinion in glycemic targets within the diabetes community (see Table 1).[1,2] Singer offers the general glycemic target of 90-150 mg/dL. I believe glycemic targets should be reassessed and adjusted based on the patient's clinical presentation. Patient safety is the most important factor in determining glycemic targets. The presence of nausea and vomiting, ability to tolerate food, and a patient's activity level should be evaluated before deciding on a glycemic target and choice of medication regimen.One should also take into account the patient's prognosis and desire to achieve glycemic control. Some patients may desire tight glycemic control as a means of exerting some degree of control over an otherwise untenable situation. Tight glycemic control to avoid chronic complications of diabetes is not an issue for a patient who will not live long enough to develop complications. Nevertheless, because glycemic control can improve quality of life substantially, it should be considered when determining palliative and comfort care measures; for these patients, a blood glucose target of 90-200 mg/dL may suffice.


The section on medications is a well-organized summary of the various oral and injectable agents used to treat diabetes. Several details were not included that would be useful in the care of patients with comorbid diabetes and cancer. For instance, premeal dosing of rapid-acting insulin analogs, or of the nonsulfonylurea secretagogues nateglinide (Starlix) and repaglinide (Prandin), is a safer choice in patients who may have unpredictable PO intake or may suffer the medication side effects of nausea and vomiting. Glipizide (inactive metabolites) and glimepiride (substantial biliary/fecal metabolite excretion) are the preferred sulfonylureas in patients with renal disease. Metformin should be discontinued in cases of creatinine levels of 1.4 mg/dL or higher in women and 1.5 mg/dL or higher in men. It may take up to 12 weeks before the patient experiences the full therapeutic effects of rosiglitazone (Avandia) and pioglitazone (Actos).[3] In addition, there are numerous combinations of sulfonylurea/ biguanide, sulfonylurea/thiazolidinedione, and biguanide/thiazolidinedione pills.

Insulin may be the most psychologically daunting of all the diabetes medications, but it is often the best way to manage steroid-induced hyperglycemia and insulin resistance in patients with pre-existing diabetes. It can also be titrated daily until the patient reaches therapeutic target goals. Many patients prefer insulin pens over the traditional syringe and vial because they are easier to use. Both insulin syringes and insulin pen needles come in a standard 1/2 inch and "short" 5/16 inch length. Pen needles also are available in a "mini" 3/16 inch length. Insulin becomes a much more acceptable option when it is administered using a short-needle or mini-needle!

Oncology nurses are at the forefront in terms of monitoring patient responses to therapies. Knowledge of risk factors for diabetes, and vigilant assessment, will aid in detecting development or exacerbation of diabetes. Prompt intervention(s) may improve clinical outcomes for patients with comorbid diabetes and cancer. Nurses interested in learning more about diabetes can refer to the American Diabetes Association publication, Complete Nurse's Guide to Diabetes Care,[4] an invaluable reference book written by, and for, nurses.


1. American Diabetes Association: Standards of Medical Care in Diabetes—2007. Diabetes Care 30(suppl 1):S10, S27-S29, 2007.

2. American College of Endocrinology Position Statement on Inpatient Diabetes and Metabolic Control. Endocrine Pract 10(1):79-80, 2004.

3. Inzucchi, S: Diabetes Facts and Guidelines 2007, pp 47-50. New Haven, Yale Diabetes Center, 2007.

4. Childs B, Cypress M, and Spollett, G (eds): Complete Nurse's Guide to Diabetes Care. Alexandria, Virginia, American Diabetes Association, 2005.