Table 7.

Synthesis of studies investigating microbiome during radio- or chemoradiotherapy in patients with head and neck cancer.

References	Cancer	Treatment	Number of Patients; n	Method	Time Point for Measurements	Conclusion	Full Mouth Clinical Examination	Materials
Hou et al. [48].	HNC	RT	19	16S rRNA, V4 gene	8 points: before RT, 10, 20, 30, 40, 50, 60, 70 Gy	20 genera—significantly positively associated with their radiation dose; 10 genera—negatively associated	+	swabs
Vesty et al. [50].	HNC	RT/CRT	19	16S rRNA, V3-V4 gene ITS1/ITS2 for fungi	3 points: 0–20; 21–40; 41–60 Gy	microbiota remain stable during RT; periopathogenic genera Porphyromonas and Tannerella, were all positively correlated with ≥ grade 2 OM	−	Saliva, swabs
Zhu et al. [58].	HNC	RT/CRT	19	16S rRNA, V4 gene	8 points: before RT, 10, 20, 30, 40, 50, 60, 70 Gy	1. increase in the relative abundance of some Gram-negative bacteria; 2. severe mucositis harbored a significantly lower bacterial alpha diversity and higher abundance of Actinobacillus	+	swabs
Reyes-Gibby et al. [59].	HNC	RT/CH/CRT	66	16S rRNA, V4 gene	8 points	Changes in the abundance of genera over the course of treatment were associated with the onset of severe OM.	−	swabs
Hu et al. [60].	HNC	RT	8	16S rRNA, V1-V3 gene	2 points: before and after RT	Temporal variation of major cores in relative abundance, negative correlation between the number of OTUs and radiation dose	+	Supragingival plaque
Hu et al. [61].	HNC	RT	8	16S rRNA, V1-V3 gene	7 points: once per week	Fluctuations in gen era synergistically involved in the development of RIOM	+	Supragingival plaque

HNC—head and neck cancer; RT—radiotherapy; CT—chemotherapy; CRT—chemoradiotherapy, rRNA—ribosomal ribonucleic acid; OM—oral mucositis; OTU—Operational taxonomic unit; RIOM– radiation-induced oral mucositis.