## 1 Introduction  
Cancer is one of the leading causes of morbidity and mortality worldwide [1], representing a significant public health challenge on a global scale [2]. In 2020, it was responsible for approximately one in six deaths globally [3]. Breast and prostate cancer, in particular, represent a significant burden to global health: breast cancer is the most commonly diagnosed malignancy and the leading cause of cancer-related death in women across more than 100 countries, while prostate cancer is the most frequent among men. Together, they account for 11.7% and 7.3% of new cases, respectively [4; 5]. In 2018, the World Cancer Research Fund estimated that approximately 18% of all cancer cases in the United States could be attributed to physical inactivity, poor diet, and/or excess adiposity [6]. In this context, adopting a healthy lifestyle is considered an important protective factor and an effective tool in cancer prevention and control [7]. Cancer treatment is typically multimodal. In the case of breast cancer, conservative surgery followed by radiotherapy is common and has been associated with a 21.7% reduction in local recurrence at 10 years, a 5.4% reduction in breast cancer mortality, and a 5.3% reduction in all-cause mortality at 15 years [8]. For prostate cancer, prostatectomy is a frequent intervention, often combined with radiotherapy [9]. Chemotherapy is also commonly used to prevent recurrence in patients with stage I-III cancer, alongside immunotherapy in certain cases [10; 11]. However, these treatments can induce multiple adverse effects, including fatigue, pain, cognitive impairment, sarcopenia, osteoporosis, and cardiotoxicity, among others [12; 13; 14; 15]. Fatigue is among the most prevalent and debilitating symptoms experienced by cancer patients [16], often persisting for years after treatment completion [17]. Cancer-related fatigue is defined by the National Comprehensive Cancer Network as \"a distressing, persistent, and subjective sense of physical, emotional, and/or cognitive tiredness or exhaustion related to cancer or its treatment, which is not proportional to recent activity and interferes with usual functioning\" [18]. It affects physical, emotional, and cognitive domains; tends to be disproportionate to the level of exertion; and significantly interferes with patients' daily functioning [19]. Fatigue may even occur prior to treatment initiation and is frequently exacerbated during chemotherapy [20], radiotherapy [21], or hormone therapy [22]. This condition negatively impacts functional capacity, activities of daily living, and emotional well-being, and may predict lower overall survival and recurrence-free survival [19; 23]. Given the high prevalence and impact of cancer-related fatigue, numerous non-pharmacological interventions have been studied to alleviate it [24]. Among these, therapeutic exercise has been shown to be an effective strategy with a strong benefit-risk profile [18; 24; 25]. Therapeutic exercise programs have demonstrated positive effects in reducing cancer-related fatigue [24; 25], as well as additional benefits for quality of life, strength, and overall physical function [26]. Among the variables influencing exercise program outcomes, supervision stands out as a key factor [27]. Supervised programs provide continuous professional guidance, which can enhance adherence and improve intervention effectiveness [28; 29; 30]. They also ensure proper technique, reduce the risk of injury [31], and allow for tailored adjustments of intensity and exercise type based on the patient's physical condition [30]. The American Society of Clinical Oncology (ASCO) also supports supervised exercise, highlighting that both aerobic and combined aerobic-resistance training are effective in reducing fatigue among cancer patients [32]. In contrast, unsupervised programs, while offering greaterflexibility and accessibility, may compromise adherence, increase perceived exertion, and reduce safety [28; 29; 30; 31], which can ultimately diminish the program's benefit-risk balance.