Purpose of Study In both FOLFOX and FOLFIRI regimens used for colorectal cancer, the 5-FU is infused over 46 hours every 14 days. Given the 10–20% risk of neutropenic fever, these regimens may be given with pegfilgrastim support. There is evidence to support its use for 21 day cycles, but no phase III trials demonstrating its efficacy and safety for regimens given every 14 days, a potential concern, given the hypothesis that the hematopoietic stem cells mobilized by pegfilgrastim into the peripheral blood may undergo cell cycle arrest, apoptosis and death while under effect of chemotherapy. Pegfilgrastim regulates the proliferation, differentiation, and survival of the myeloid lineage. It mobilizes hematopoietic progenitor cells in the peripheral circulation, has a long half-life, and is given on day 4 of 14-day infusional 5-FU based regimens. Given the fact that cytotoxic chemotherapy is administered on day 11 after pegfilgrastim, we performed a retrospective study evaluating the correlation between decrease in complete blood count and chemotherapy administered at 11 day intervals after pegfilgrastim.
Methods Used The medical records of colorectal cancer patients were reviewed from 2003–2013. Data collected included age, stage, ethnicity, complete blood count, chemotherapy, and use of pegfilgrastim.
Summary of Results Data from 50 eligible charts was collected. Twenty one patients were treated with chemotherapy and pegfilgrastim, 29 patients had chemotherapy alone. Prior to chemotherapy, both groups had a mean leukocyte count of 6.6×109/L and 6.8×109/L and a mean platelet count of 313,000/mm3 and 255,000/mm3 respectively. At 9 months mean leukocyte counts were 6.3×109/L and 5.4×109/L and the mean platelet counts were 186,000/mm3 and 170,000/mm3 respectively. At 24 months, the mean leukocyte counts were 6.7×109/L and 5.7×109/L and the mean platelet counts were 220,000/mm3 and 196,000 mm3 respectively.
Conclusions When given on day 4 of a 14 day cycle, there was no effect of pegfilgrastim on complete blood counts in this small retrospective cohort study; finding a more subtle effect would require a larger sample size.
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