An in vitro method of predicting the sensitivity of a cell to a selected dose of radiation therapy, the method comprising: assigning a radiation sensitivity index to the cell the index generated by applying a linear regression model to expression levels of a subset of signature genes in the cell, selected from the group consisting of Androgen receptor; Jun oncogene (c-Jun); Signal transducer and activator of transcription 1 (STAT1); Protein kinase C, beta (PRKCB or PKC); V-rel reticuloendotheliosis viral oncogene homolog A (avian) (RELA or p65); c-Abl oncogene 1, receptor tyrosine kinase (ABL1 or c-Abl); SMT3 suppressor of mif two 3 homolog 1 (S. cerevisiae) (SUMO1); PAK2; Histone deacetylase 1 (HDAC1); and Interferon regulatory factor 1; wherein the radiation sensitivity index indicates whether the cell is sensitive to radiation therapy; and wherein (i) the subset of signature genes comprise AR, c-jun, STAT1, cAbl, SUMO1, and IRF1; (ii) the subset of signature genes comprise c-jun, STAT1, RelA, cAbl, SUMO1, and IRF1; (iii) the subset of signature genes comprise c-jun, STAT1, PKC, RelA, cAbl, HDAC, and IRF1; (iv) the subset of signature genes comprise AR, c-jun, STAT1, PKC, RelA, cAbl, HDAC, and IRF1; (v) the subset of signature genes comprise AR, c-jun, STAT1, PKC, RelA, cAbl, PAK2, HDAC, and IRF1; or (vi) the subset of signature genes comprise AR, c-jun, STAT1, PKC, RelA, cAbl, SUMO1, PAK2, HDAC, and IRF1. assigning a radiation sensitivity index to the cell the index generated by applying a linear regression model to expression levels of a subset of signature genes in the cell, selected from the group consisting of Androgen receptor; Jun oncogene (c-Jun); Signal transducer and activator of transcription 1 (STAT1); Protein kinase C, beta (PRKCB or PKC); V-rel reticuloendotheliosis viral oncogene homolog A (avian) (RELA or p65); c-Abl oncogene 1, receptor tyrosine kinase (ABL1 or c-Abl); SMT3 suppressor of mif two 3 homolog 1 (S. cerevisiae) (SUMO1); PAK2; Histone deacetylase 1 (HDAC1); and Interferon regulatory factor 1; wherein the radiation sensitivity index indicates whether the cell is sensitive to radiation therapy; and wherein (i) the subset of signature genes comprise AR, c-jun, STAT1, cAbl, SUMO1, and IRF1; (ii) the subset of signature genes comprise c-jun, STAT1, RelA, cAbl, SUMO1, and IRF1; (iii) the subset of signature genes comprise c-jun, STAT1, PKC, RelA, cAbl, HDAC, and IRF1; (iv) the subset of signature genes comprise AR, c-jun, STAT1, PKC, RelA, cAbl, HDAC, and IRF1; (v) the subset of signature genes comprise AR, c-jun, STAT1, PKC, RelA, cAbl, PAK2, HDAC, and IRF1; or (vi) the subset of signature genes comprise AR, c-jun, STAT1, PKC, RelA, cAbl, SUMO1, PAK2, HDAC, and IRF1. (i) the subset of signature genes comprise AR, c-jun, STAT1, cAbl, SUMO1, and IRF1; (ii) the subset of signature genes comprise c-jun, STAT1, RelA, cAbl, SUMO1, and IRF1; (iii) the subset of signature genes comprise c-jun, STAT1, PKC, RelA, cAbl, HDAC, and IRF1; (iv) the subset of signature genes comprise AR, c-jun, STAT1, PKC, RelA, cAbl, HDAC, and IRF1; (v) the subset of signature genes comprise AR, c-jun, STAT1, PKC, RelA, cAbl, PAK2, HDAC, and IRF1; or (vi) the subset of signature genes comprise AR, c-jun, STAT1, PKC, RelA, cAbl, SUMO1, PAK2, HDAC, and IRF1.