According to a pooled analysis of studies, higher rates of pre-existing fatigue in cancer patients are associated with a higher risk of severe or worse toxic effects with systemic treatment. The research was based on 17 studies from the SWOG Cancer Research Network. Cancer-related fatigue differs from normal fatigue in that the patient cannot easily help it and it is not preceded by increased exertion. This fatigue significantly reduces patients' physical activity, and up to 60% of patients reported that it prevents them from continuing to work. According to studies, up to 72% of lymphoma patients experience fatigue that affects their lives. The findings highlight the need to monitor fatigue before starting systemic treatment so that health professionals can better prepare for possible toxic effects and tailor treatment individually.