What prophylactic pegfilgrastim dose should be given to a 50‑year‑old woman with right‑sided breast cancer undergoing dose‑dense doxorubicin and cyclophosphamide neoadjuvant chemotherapy who weighs 43.5 kg?

Pegfilgrastim Dosing for Dose-Dense AC Chemotherapy

Administer pegfilgrastim 6 mg subcutaneously on day 2 (approximately 24 hours after chemotherapy completion) for each cycle of dose-dense AC chemotherapy, regardless of the patient's weight of 43.5 kg. 1

Standard Fixed Dosing

• The FDA-approved dose of pegfilgrastim is 6 mg as a single subcutaneous injection per chemotherapy cycle, administered approximately 24 hours after cytotoxic chemotherapy. 1
• This is a fixed dose that does not require weight-based adjustment, even though your patient weighs only 43.5 kg. 1
• The dose-dense AC regimen (doxorubicin 60 mg/m² and cyclophosphamide 600 mg/m² every 14 days for 4 cycles) explicitly requires filgrastim support with all cycles according to NCCN guidelines. 2

Evidence Supporting Fixed 6 mg Dose

• Clinical trials establishing pegfilgrastim efficacy in breast cancer patients receiving dose-dense chemotherapy used the 6 mg fixed dose, demonstrating a febrile neutropenia rate of only 1.5% (2/135 patients). 3
• The 6 mg dose was tested in patients ranging from 21 to 88 years of age with varying body weights, confirming efficacy across the weight spectrum. 1
• A Japanese study using a reduced 3.6 mg dose showed efficacy in Asian patients with dose-dense AC, but this lower dose is not FDA-approved and should not be used in standard practice. 4

Critical Administration Details

• Administer pegfilgrastim on day 2 of each chemotherapy cycle (the day after chemotherapy, not the same day). 1, 3
• Do not administer pegfilgrastim in the period 14 days before to 24 hours after administration of cytotoxic chemotherapy due to potential sensitivity of rapidly dividing myeloid cells. 1
• Continue pegfilgrastim with each of the 4 cycles of dose-dense AC, then continue with each of the 4 subsequent paclitaxel cycles (also given every 14 days). 2, 3

Monitoring Requirements

• Monitor complete blood count before each chemotherapy cycle to assess for neutropenia recovery. 1
• Watch for bone pain (occurs in approximately 31% of patients receiving pegfilgrastim versus 26% with placebo), which is the most common adverse effect. 1
• Monitor for rare but serious complications including splenic rupture, acute respiratory distress syndrome, and allergic reactions. 1

Common Pitfall to Avoid

Do not use weight-based dosing for pegfilgrastim. Although older formulations used 100 mcg/kg dosing in some trials, the current FDA-approved and guideline-recommended approach is the fixed 6 mg dose. 1, 5 The fixed dose simplifies administration and has been validated across diverse patient populations, including those with low body weight like your patient. 1