Zack is a 12-year-old boy who had been in good health with no significant medical history until 6 months ago. At that time, he began to experience episodic migraine-like headaches, and with a paternal family history of migraines, Zack was evaluated for possible antimigraine therapy if the headaches continued. After 3 months of increasing severity of the headaches, he was diagnosed by CT scan with a brain tumor. Zack underwent craniotomy for evacuation of a malignant tumor and began chemotherapy 1 month after surgery, prior to planned radiation therapy treatments. He has completed one cycle of chemotherapy over 2 months and will have a second cycle prior to radiation. He visits the oncology clinic today for evaluation prior to his second round of chemotherapy. Physical examination on this clinic visit reveals a pleasant young male in no obvious distress. Zack weighs 43.6 kg (96 lb) and is 157.5 cm (62 in.) in height. BP is 92/40 mmHg, pulse rate is 92 beats/min, respirations of 24 breaths/ min, and temperature of 37.1°C (98.8°F). Zack denies having any pain and his neurologic exam is unremarkable except for diminished patellar DTRs, graded at 1 (decreased but present; normal of 2). His WBC count is 3,420/mm 3; ANC, 1,800; haemoglobin (Hgb), 13 g/dL; hematocrit (Hct), 36.5%; and his platelet count is 225,000. CBC is within the range expected post chemotherapy. Zack will be hospitalized for approximately 2 days for administration of cyclophosphamide (Cytoxan), carboplatin (Paraplatin), and vincristine (Oncovin), and will continue to receive doses of vincristine as an outpatient and start etoposide (VePesid) in several weeks. Because he experienced significant nausea and vomiting with the last round of chemotherapy, he will also be given ondansetron (Zofran) regularly with supplemental corticosteroids IV as needed.
1. Why are four antineoplastic drugs used for Zack? What is the pharmacologic classification of each of the drugs used?
2. What overlapping toxicities might Zack experience with these drugs? Considering his physical assessment findings from today, what system toxicities would be of most concern?
3. Fifteen days after the start of the second cycle of chemotherapy, Zack experiences his nadir. At this time his WBC count is 340/mm 3; ANC, 98; Hgb, 9.3 g/dL; Hct, 25.7%; and the platelet count is 55,000. Zack has been receiving filgrastim (Neupogen) subcutaneously since discharge and will continue until the WBC count begins to rise. Considering these laboratory values, what would be of most concern to the oncology team? What teaching should Zack and his family receive?