What to do with a patient on chemotherapy for a rectal mass who develops leukocytosis (elevated White Blood Cell (WBC) count)?

From the FDA Drug Label

In patients with cancer receiving ZARXIO as an adjunct to myelosuppressive chemotherapy‚ to avoid the potential risks of excessive leukocytosis‚ it is recommended that ZARXIO therapy be discontinued if the ANC surpasses 10‚000/mm3 after the chemotherapy-induced ANC nadir has occurred. White blood cell counts of 100‚000/mm3 or greater were observed in approximately 2% of patients receiving filgrastim at dosages above 5 mcg/kg/day During the period of administration of ZARXIO for PBPC mobilization in patients with cancer, discontinue ZARXIO if the leukocyte count rises to > 100,000/mm3.

Management of Critically High WBC in a Patient on Chemo for Rectal Mass:

• Discontinue filgrastim (ZARXIO) therapy if the ANC surpasses 10,000/mm3 after the chemotherapy-induced ANC nadir has occurred.
• Monitor CBCs at least twice weekly during therapy.
• Consider discontinuing filgrastim therapy if the leukocyte count rises to > 100,000/mm3. 1

From the Research

For a patient on chemotherapy for a rectal mass who develops leukocytosis, prompt evaluation for neutropenic fever or infection is essential, and immediate empiric antibiotic therapy may be needed, as supported by the principles outlined in 2. When managing a patient with a critically high WBC count on chemotherapy for a rectal mass, it's crucial to first assess for signs of infection or neutropenic fever. This involves obtaining a complete blood count with differential, blood cultures, and urinalysis, as well as checking vital signs and assessing for signs of infection such as cough, abdominal pain, perianal tenderness, or catheter site inflammation.

• If neutropenic fever is present (temperature ≥38.3°C and absolute neutrophil count <500/mm³), immediate empiric antibiotic therapy is necessary, typically with an antipseudomonal beta-lactam like piperacillin-tazobactam 4.5g IV every 6 hours or cefepime 2g IV every 8 hours, as these are standard treatments for neutropenic fever.
• For non-neutropenic patients with signs of infection, targeted antibiotics based on the suspected source should be initiated.
• Consider temporarily holding chemotherapy until the infection resolves, as the primary concern is the patient's immediate health and safety. The elevated WBC count may be due to infection, inflammation, steroid use, or a physiologic response to chemotherapy itself. Chemotherapy-induced myelosuppression typically causes leukopenia rather than leukocytosis, so an elevated count warrants investigation for other causes, particularly infection which can be life-threatening in immunocompromised patients, as discussed in 3 and 2. Key considerations include:
• Distinguishing between malignant and benign leukocytosis, as outlined in 2.
• Understanding the potential for myeloid leukemoid reactions versus myeloid malignancies, and the importance of a bone marrow examination and appropriate ancillary studies for diagnosis, as noted in 2.
• Recognizing that an elevated WBC count in the context of cancer and venous thromboembolism may be associated with an increased risk of complications, including recurrent VTE, major bleeding, or death, as found in 3. Given the complexity and potential severity of leukocytosis in a patient on chemotherapy for a rectal mass, a thorough and prompt evaluation is critical to guide appropriate management and prevent adverse outcomes, as implied by the need for careful assessment and intervention in such cases 4, 5, 6.