This is a phase II multicenter study designed in two phases. A total of 32 patients will be included in 10 hospitals belonging to the Spanish Group for Research in Sarcomas (GEIS). Selection criteria are: patients with localized soft tissue sarcoma from the extremities or trunk with high-risk features (>5 cm and grade 2-3), or recurrences after prior inadequate surgery. The treatment schedule will be: initial biopsy, 3 cycles of high-dose Ifosfamide, 12 gr/m2 in 5 days, concurrent with Radiotherapy 50 Gy, and subsequent wide surgery. To assess the predictive factors of response to the combination therapy, DNA and RNA extraction will be performed on the pretreatment biopsies. DNA will be used to hybridize Affymetrix GeneChip® Human Mapping 500K Array, which allows for the study of 500000 SNPs throughout the genome. The expression of 39000 RNA transcripts will be evaluated employing the Affymetrix Genechip Human Genome HG-U133 Plus 2.0, and validated by real-time RT-PCR.