Oral cancer affects hundreds of thousands of people worldwide. Little is known, however, about how this cancer and its treatment affect the oral microbiome. To find out, researchers investigated changes in the salivary microbiome of patients treated for oral squamous cell carcinoma vs. healthy controls. Oral cancer overall was associated with a higher abundance of potentially pathogenic bacteria in patients before treatment compared to healthy, including Streptococcus anginosus, Abiotrophia defectiva, and Fusobacterium nucleatum. And cancer treatment was found to contribute to further changes in the oral microbiome vs. pre-treatment and healthy, such as lower microbial diversity, with some of these changes persisting for several years after treatment. While the researchers did not explore patients’ full oral examination records, and only a small number of patients were available for follow-up, the findings are informative. They highlight the importance of preventive measures in the aftercare of patients with oral cancer, such as the use of pre- or probiotics, salivary substitutes, or dietary counseling, and they contribute to a better understanding of the relationship between oral cancer, its treatment, and the salivary microbiome.