BACKGROUND: The most serious disturbance of the nutritional status is neoplastic cachexia. The main factor contributing to the development of cachexia is the ongoing inflammatory process. The gene associated with the development of the inflammatory response is . Therefore, the aim of the study was to assess the relationship between a single nucleotide polymorphism (SNP)-323G>A of the gene and the occurrence of nutritional disorders in patients undergoing radiotherapy (RT) due to head and neck cancers (HNC). METHODS: The study involved 71 patients with HNC treated with intensity-modulated radiotherapy (IMRT). SNP analysis of the gene (-323G>A) was performed using commercial molecular probes and Real-Time PCR. RESULTS: The presence of the A allele of the gene significantly (over 14-fold) reduced the risk of severe disturbances in nutritional status assessed according to the subjective global assessment (SGA) scale (odds ratio (OR) = 0.07; = 0.0213). The GG genotype of this gene was associated with an over three-fold higher risk of shortened overall survival (OR = 3.01; = 0.0376). CONCLUSIONS: Determination of the SNP (-323G>A) of the gene may prove to be a useful marker in the assessment of the risk of nutritional disorders in patients with HNC undergoing RT.