The effectiveness and tolerability of medicines can vary considerably from person to person, even at the same dose. This variation is influenced by many factors, including constitutional genetic characteristics. In fact, some people have genetic variations that are common and neutral in the population, known as polymorphisms, which can affect drug metabolism or make them more susceptible to certain adverse effects. These variations can lead to dose-dependent toxicity in the case of genetic polymorphisms of metabolic enzymes or hypersensitivity to drugs. Pharmacogenetics therefore examines the specific genetic factors of each patient to understand their sensitivity to treatment and their risk of developing side effects. By enabling proactive adjustment of dosage and/or treatment, pharmacogenetics minimizes the risk of adverse effects and offers promising prospects for a more personalized approach to tumour management. This review will focus on the potential of pharmacogenetics in cancer care, from cancer treatment to supportive care. It will provide an overview of pharmacogenetic recommendations from national and international scientific and professional societies that are currently used in clinical practice. In addition, we will discuss the challenges and perspectives associated with integrating pharmacogenetics into clinical practice for more personalized management of cancer patients.