9621 Background: Bone pain is the most commonly reported treatment-related adverse event (AE) associated with colony-stimulating growth factors. Some authors have suggested that pegfilgrastim-induced bone pain is unpredictable and refractory to analgesics (Kirshner 2007), though that impression may not be uniformly accepted. To better characterize this adverse event we evaluated bone pain across pegfilgrastim clinical trials. Methods: Completed Amgen-sponsored trials that both incorporated pegfilgrastim 6mg administered 24 hours after chemotherapy and utilized MedDRA library coding of AEs were examined. Included were 2 studies comparing pegfilgrastim with placebo (Vogel 2005, Hecht 2007) and 2 studies comparing pegfilgrastim with filgrastim (Sierra 2008, Lopez 2004). The incidence of bone pain was determined by treatment (pegfilgrastim, filgrastim, or placebo), chemotherapy (taxane-containing or not), cycle, severity, age, and body surface area (BSA). Analysis and recoding of studies with preferred AEs coded to nonMedDRA dictionaries is ongoing. Results: 1310 pts (filgrastim=67, pegfilgrastim=665, placebo=578) were analyzed. In studies comparing pegfilgrastim (n=74) and filgrastim (n==7) in pts with AML and NHL, 52% were female, and the mean (SD) age was 50 (15.1) years. Similar proportions (CI) of pts reported bone pain (24.3% [16.1, 35.7] vs 25.4% [15.5, 37.5], respectively), and grade 3/4 bone pain was reported in 3% [0.3, 9] versus 0% [-, -] of pts, respectively. Studies comparing pegfilgrastim (n=591) and placebo (n=578) pts in breast and colorectal cancer are below ( Table ). Conclusions: Bone pain of any grade was commonly reported in all 3 groups (pegfilgrastim, filgrastim, and placebo) and was marginally higher in pts receiving pegfilgrastim compared with placebo. Bone pain was most common in cycle 1. Severe bone pain was infrequently reported. Bone pain was similar in pts receiving pegfilgrastim and filgrastim. Chemotherapy (eg, taxanes) may also contribute to bone pain. [Table: see text] [Table: see text]