Among the focus genes in our study, the genes most commonly assessed for their association with mucositis were ERCC1, XRCC1, and MTHFR. The results of the IPA suggest that the top focus genes, in terms of the number of connections, in mucositis were CDKN1A (p21) and BRCA1; the novel molecules identified through the IPA were TP53, CTNNB1, MYC, RB1, P38 MAPK, and EP300. This evidence concerns the gene MAPK1 and mucositis.