Blood samples are collected at baseline, 32 days, and 100 days after HSCT to evaluate the immunogenicity of palifermin. Oral mucositis is assessed at baseline, daily for 8 days prior to and 32 days after HSCT, or until oral mucositis has resolved by the WHO Mucositis Scale, Oral Mucositis Assessment Scale (OMAS), modified Walsh mucositis scale, Oral Mucositis Daily Questionnaire (OMDQ), and the pain categorical rating scale.