Should thyroid‑stimulating hormone (TSH), hemoglobin A1c (HbA1c), and morning cortisol levels be obtained before initiating bevacizumab (Avastin) therapy?

TSH, HbA1c, and Morning Cortisol Before Bevacizumab

No, TSH, HbA1c, and morning cortisol are not required before initiating bevacizumab therapy according to current guidelines and FDA labeling.

What Is Actually Required Before Bevacizumab

The available guidelines and FDA drug labeling do not mandate measurement of TSH, HbA1c, or morning cortisol prior to bevacizumab initiation 1, 2. The primary pre-treatment requirement is:

Blood Pressure Assessment

• Measure clinic blood pressure before starting bevacizumab 1
• Bevacizumab can only be initiated if clinic BP is <160/100 mmHg
• If BP is ≥160/100 mmHg, confirm with ambulatory or home BP monitoring (ABPM/HBPM)
• Target ABPM/HBPM <150/95 mmHg before starting therapy

Why These Tests Are Not Standard Requirements

TSH (Thyroid Function)

While thyroid dysfunction can occur during bevacizumab therapy, particularly when combined with immune checkpoint inhibitors like atezolizumab, baseline TSH is not a standard requirement 3, 4. Thyroid adverse events:

• Occur in approximately 19.7% of patients receiving atezolizumab/bevacizumab combination 4
• Typically develop 1-3 months after treatment initiation 3, 4
• Are monitored during treatment, not screened beforehand

Clinical caveat: If bevacizumab is being used with immune checkpoint inhibitors, some experts recommend baseline thyroid autoantibodies as a risk stratification tool 3, but this is not universally mandated.

HbA1c (Glycemic Control)

The FDA label and guidelines do not require HbA1c measurement before bevacizumab 2. While:

• Better glycemic control may improve response to anti-VEGF therapy in diabetic macular edema 5
• This is relevant for ophthalmologic indications, not systemic cancer therapy
• No evidence supports mandatory HbA1c screening before bevacizumab for oncologic indications

Morning Cortisol

There is no requirement or rationale for measuring morning cortisol before bevacizumab therapy in the available evidence 1, 2. This test is not mentioned in any guideline or drug labeling for bevacizumab.

What Should Actually Be Done Pre-Treatment

Based on FDA labeling and expert guidelines 1, 2:

1. Blood pressure measurement (mandatory)

   • Clinic BP must be <160/100 mmHg
   • Consider ABPM/HBPM if borderline

2. Urinalysis for proteinuria (recommended monitoring)

   • Bevacizumab can cause proteinuria and renal thrombotic microangiopathy 2

3. Pregnancy testing (if applicable)

   • Bevacizumab causes fetal harm 2
   • Contraception required during and 6 months after treatment

4. Assessment of bleeding risk and recent surgeries

   • Bevacizumab increases hemorrhage risk 2
   • Avoid within 28 days of major surgery

Monitoring During Treatment

Before each bevacizumab infusion 1:

• Measure blood pressure (must be <160/100 mmHg to proceed)
• Assess for proteinuria periodically
• Monitor for arterial thromboembolic events, especially in patients ≥65 years 2

Common pitfall: Clinicians sometimes order extensive baseline laboratory panels unnecessarily. Focus on the evidence-based requirements: blood pressure control, pregnancy status, and surgical/bleeding history.