Introduction and objective:
Cancer is one of the greatest challenges of modern medicine. Therapeutic difficulties, such as treatment resistance and the complexity of the tumour microenvironment are driving the search for new strategies. There is growing interest in the human microbiome as a factor influencing cancer progression and response to treatment. The aim of this study is to present the state of knowledge on the effect of microbiome on cancer development and to discuss the mechanisms of these interactions.

Brief description of the state of knowledge:
Human microbiome plays a key role in oncology through complex mechanisms. Research points to the dual nature of its interactions. On the one hand, dysbiosis and the presence of pathogenic bacteria, such as Fusobacterium nucleatum in colorectal cancer, or Helicobacter pylori in gastric cancer, promote carcinogenesis through induction of inflammation, production of genotoxins and suppression of the immune response. On the other hand, bacteria such as Akkermansia muciniphila or Bifidobacterium show protective effects through, among other things, short-chain fatty acids and modulation of the immune system. The presence of beneficial microorganisms has been linked to a better response to immunotherapy (e.g. PD-1 inhibitors) in the treatment of lung cancer or melanoma. These relationships also apply to skin cancer, where Staphylococcus epidermidis may have a protective effect, and Staphylococcus aureus a procancerogenic effect.

Summary:
The composition of the microbiota can serve as a predictive biomarker of response to cancer treatment. Targeted modulation of the microbiome – through diet, probiotics, prebiotics or faecal microbiota transplantation (FMT) – is emerging as a promising strategy to support standard cancer therapies, paving the way for the development of more personalised oncology.