What is the problem
Diabetes Mellitus (DM) is broadly separated into patients with Type 1 Diabetes (T1D) who have autoimmune destruction of islet cells resulting in insulin deficiency, and those with Type 2 Diabetes (T2D) who have insulin resistance. However, in the oncological setting other diabetes types are also prevalent:
- Glucocorticoid induced diabetes (GID) in the setting of prolonged, high dose glucocorticoids
- Type 3c Diabetes (T3cDM) in the setting of pancreatectomy or pancreatic infiltration by malignancies
- Immune related Diabetes (ir-T1cDM) in the setting of checkpoint inhibitor-associated autoimmune destruction of islet cells.
Poor glycemic control is known to result in increased morbidity such as infection, reduced efficacy of chemotherapy1, adverse effects from therapy, requirement for treatment modifications and increased emergency department visits2.
Who should be tested
All at-risk pre-operative patients should be screened for DM or be assessed for DM control. More than 1 in 20 Australians have DM, with the prevalence increasing to 1 in 5 older Australians3. Furthermore, undiagnosed DM prevalence from the general-practice-based Australian Diabetes Screening Study was 16%.
Risk factors for DM include4,5:
- known DM
- cardiovascular risk factors
- BMI > 25
- age > 40 years
- glucocorticoid use
- family history of DM
Other causes of hyperglycemia in the oncology setting includes glucocorticoids, chemotherapy, everolimus etc, which might not be immediately reversible. Those with newly diagnosed DM are treated in the same way as individuals with known DM.
What tests should be ordered
HbA1c should be checked as a screening test for all at-risk patients4,5. HbA1c reflects the average blood glucose over the previous 3 months, and therefore can diagnose DM or monitor DM control.
HbA1c may be unreliable in certain situations:
- falsely low after blood transfusion, blood loss, or reduced red cell lifespan (i.e. haemolysis)6.
- falsely elevated with prolonged red cell lifespan such as iron-deficiency or vitamin B12 deficiency, chronic kidney disease.
In these situations, alternative testing such as a fasting glucose or oral glucose tolerance test may by more appropriate.
What defines diabetes
Diabetes Mellitus (DM) is defined by the Diabetes Society of Australia as meeting any of the criteria below in a non-pregnant individual7.
- HbA1c ≥6.5% (48 mmol/mol)
- Fasting glucose ≥7.0 mmol/L
- Random glucose ≥11.1 mmol/L
- On a 75 g oral glucose tolerance test: fasting glucose ≥7.0 mmol/L or 2 hr glucose ≥11.1 mmol/L.
How should diabetes be assessed pre-operatively
Newly diagnosed T2D should be managed by the patient’s GP with dietary measures along with first line oral hypoglycaemic agents (OHAs). A referral to an endocrinologist is necessary if insulin treatment is required, i.e. if the blood sugar level is high (>16 mmol/L) and surgery cannot be delayed for dietary measures and OHA therapy to take effect.
Optimal DM control aims to achieve a HbA1c of ≤ 6.5%. A pre-operative HbA1c of ≥ 10% is associated with post-operative complications and therefore ideally should be optimised prior to surgery if time permits.
DM medications also need to be withheld at different intervals prior to fasting for procedures. This is to avoid serious complications such as hypoglycaemia, acidosis and aspiration.
How will the effectiveness be evaluated
Outcome measures from this intervention will include:
- Defining local epidemiology and prevalence of elevated pre-operative HbA1c in surgical oncology patients
- Measuring toolkit testing compliance, defined as the completion and follow-up of HbA1c in all pre-operative patients, and appropriate cessation/ adjustment of DM medications pre-operatively
- The efficacy of the program is evaluated via
- Perioperative hyper/ hypoglycemia rates
- Complications from DM therapies (e.g. eDKA)
- LOS, infection rate, readmission rate.