What blood tests and how often should be done for patients on Temozolomide (temozolomide) therapy?

From the Guidelines

Patients on temozolomide therapy should have complete blood count (CBC) with differential monitored regularly throughout treatment, with a baseline CBC obtained before starting treatment, and then checked weekly for the first 6 weeks of treatment, then every 2-4 weeks thereafter for the duration of treatment, as supported by 1 and 1.

Monitoring Schedule

The monitoring schedule for patients on temozolomide therapy should include:

• Baseline CBC with differential before starting treatment
• Weekly CBC checks for the first 6 weeks of treatment
• Every 2-4 weeks thereafter for the duration of treatment
• More frequent monitoring may be necessary for patients who develop cytopenias

Laboratory Tests

The following laboratory tests should be monitored:

• Complete blood count (CBC) with differential
• Liver function tests (LFTs) periodically, typically at baseline and then monthly during treatment

Adjusting Monitoring Frequency

The frequency of monitoring may need to be adjusted based on individual patient factors such as:

• Age
• Prior treatments
• Baseline blood counts
• Concurrent medications

Primary Concerns

The primary concerns with temozolomide therapy are:

• Myelosuppression, particularly thrombocytopenia and neutropenia, which can lead to serious complications like bleeding or infections
• Lymphopenia, which can increase the risk of opportunistic infections

Dose Adjustments

Temozolomide should be temporarily discontinued or the dose reduced if:

• Absolute neutrophil count falls below 1,500/μL
• Platelet count falls below 100,000/μL Patients with severe myelosuppression may require growth factor support or transfusions, as noted in 1 and 1.

From the FDA Drug Label

During treatment a complete blood count should be obtained weekly. During treatment, a complete blood count should be obtained on Day 22 (21 days after the first dose of temozolomide capsules) or within 48 hours of that day, and weekly until the ANC is above 1.5 x 10^9/L (1500/μL) and the platelet count exceeds 100 x 10^9/L (100,000/μL).

Blood Analysis Control for Temozolomide:

• A complete blood count should be obtained weekly during the concomitant phase.
• During the maintenance phase, a complete blood count should be obtained on Day 22 (or within 48 hours) and weekly until the ANC and platelet count exceed certain levels.
• The next cycle of temozolomide should not be started until the ANC and platelet count exceed these levels: ANC ≥ 1.5 x 10^9/L and platelet count ≥ 100 x 10^9/L 2

From the Research

Blood Analysis Control for Temozolomide Therapy

To monitor patients on Temozolomide therapy, the following blood tests and frequencies are recommended:

• Complete Blood Count (CBC) with differential and platelet count:
  • Before starting treatment 3, 4, 5, 6
  • Weekly during radiation and Temozolomide therapy 7
  • Every 4 weeks during adjuvant Temozolomide treatment 4
• Liver function tests (LFTs):
  • Weekly during radiation and Temozolomide therapy 7
  • Every 4 weeks during adjuvant Temozolomide treatment 4

Rationale for Blood Tests

The rationale for these blood tests is to monitor for potential toxicities associated with Temozolomide therapy, including:

• Myelosuppression (thrombocytopenia, neutropenia, anemia) 3, 4, 5, 6
• Liver injury (transaminitis, bilirubinemia) 7
• Biliary ductopenia (vanishing bile duct syndrome) 7

Factors Associated with Severe Myelotoxicity

Several factors have been associated with severe myelotoxicity in patients receiving Temozolomide therapy, including:

• Female sex 4
• Pretreatment platelet count ≤300,000/mm³ 4
• Methylated O-methylguanine-DNA methyltransferase promoter in the hematopoietic cell system 4
• Specific polymorphic variants of the cytochrome P450 oxidoreductase and methionine adenosyltransferase 1A genes 4