Breast cancer is the leading cause of mortality in women worldwide. Latin-American women are diagnosed at younger ages, in advanced stages, and with aggressive molecular subtypes. Lifestyle seems related to these aggressive conditions and worse outcomes. The present study seeks to evaluate the effect of a hybrid multidisciplinary intervention for implementing a healthy lifestyle to modify the personal and internal exposome of young women with breast cancer. This randomized controlled experimental study with two groups:

Group 1: Hybrid multidisciplinary lifestyle education intervention. Group 2: Individualized hybrid multidisciplinary lifestyle interventions. The multidisciplinary lifestyle intervention program includes oncology, nutrition, physiotherapy, and psychology interventions.

Breast cancer (BC) is a leading cause of death in women worldwide, especially in Latin America, where patients often present with advanced stages of aggressive subtypes of BC at a younger age. The risk of BC depends on various factors, including hormone replacement therapy history, reproductive history, alcohol or tobacco consumption, physical activity, and dietary habits, collectively called exposome. Exposome refers to the exposure to environmental influences and biological responses throughout a person's life from the prenatal stage. It can be influenced by the environment, diet, behavior, and endogenous processes.

External exposome refers to environmental factors such as mental stress, climate, and lifestyle. In contrast, internal exposome are changes within an organism, such as increased stress hormones, inflammatory cytokines, and oxidative stress. Constant exposure to environmental factors, such as an unhealthy lifestyle, can cause cellular damage and contribute to the growth and evolution of tumors. Once cellular damage occurs, internal exposome promotes changes that create a harmful environment, favoring cancer cells to acquire coping mechanisms for stress and drugs, leading to resistance to oncological treatments.

Obesity is part of the personal exposome and can impact the internal exposome, potentially affecting BC patients. A significant percentage of patients diagnosed with BC (70.9%) are overweight or obese at the time of diagnosis. This weight gain usually occurs during systemic treatment, with 25% of patients gaining weight within six months, 32% between 6-12 months, and 20% between 12-18 months after diagnosis. Young women with breast cancer (YWBC) also experience an increase in weight since the initiation of oncological treatment and up to the second year of diagnosis (from 39% at baseline to 46% in two years), highlighting the importance of evaluating the implications of weight gain and whether early intervention would help control the risk factors mentioned earlier. Obesity may also be associated with worse disease-free and overall survival.

Weight gain in patients with BC is often associated with several factors, including systemic treatment, diagnosis at a young age, and lifestyle changes resulting from the disease or treatment. However, reduced physical activity is the primary mechanism underlying weight gain. The combination of chemotherapy and endocrine therapy is linked to higher weight gain, especially in patients who are premenopausal (an increase of up to 24 kg). In contrast, postmenopausal women tend to lose weight.

BC patients have reported experiencing physical symptoms and psychological distress, which can negatively impact their quality of life (QoL). These symptoms can affect their physical functioning, psychological well-being, and social support levels. YWBC is a vulnerable population with specific concerns such as fertility, self-image, QoL, sexuality, and personal goals and experience high anxiety and depression. Maintaining a healthy lifestyle can improve QoL and lead to better prognoses and lower mortality rates. For example, exercise can reduce breast cancer-related death risk by 30% and all-cause death risk by 41%. Patients undergoing oncology treatment face various nutritional challenges that differ based on the type and stage of cancer, and the treatments may worsen these challenges. Early nutritional screening and interventions are crucial in the cancer population, as emphasized in the clinical guidelines (ASPEN/ESPEN).

The Instituto Nacional de Cancerología (INCAN) in Mexico City offers a program called "Joven & Fuerte" for young women diagnosed with BC. However, the attention was not systematic, and it was difficult to measure the benefits of the intervention. So, the present study proposes a psychological intervention, side effect management, physical activity, sleep hygiene, and psychological strategies, with onsite and remote interventions to improve patient adherence and ensure timely attention. The study aims to evaluate the impact of early intervention on metabolic control in newly diagnosed BC patients, their QoL, and clinical outcomes.

METHODS A controlled trial design was adopted in which patients were assigned to two intervention groups according to the nutritional, psychological, or rehabilitation risk at baseline or according to their geographical localization. The first group will receive a hybrid multidisciplinary lifestyle education intervention, whereas the second group will receive an individualized hybrid multidisciplinary lifestyle intervention.

Patients will be recruited through an active program at the INCAN, where potential candidates will be identified and invited by the navigator at the program "Joven & Fuerte." After they sign the informed consent form (ICF), patients will be assigned into one of the two groups:

Group 1: Hybrid multidisciplinary lifestyle education intervention. Group 2: Individualized hybrid multidisciplinary lifestyle interventions. The initial proposal was a randomized assignment to each group; however, the pilot study revealed challenges for patients who lived far from the hospital, in other states or had personal obligations such as family or work. Therefore, the randomization process was adapted to meet the patient's needs. The intervention aims to facilitate patients' adherence and follow-up with healthcare providers. Additionally, patient preferences were considered when assigning them to a group.

Objectives.

To assess the ability of a personalized lifestyle intervention to support breast cancer patients undergoing active treatment to maintain or obtain a healthy lifestyle.

To evaluate adopting a healthy lifestyle, validated questionnaires will be applied to assess lifestyle components such as level of physical activity, sleep hygiene, and emotional distress (baseline, during, and after treatment).

To evaluate changes in internal exposome parameters such as body composition, biochemical, inflammatory, and metabolomic indicators will be measured.

To evaluate the effectiveness of a virtual educational program to support breast cancer patients in active treatment to maintain or obtain a healthy personal exposome and its usefulness in patients who live in remote locations or cannot attend a face-to-face consultation.

To evaluate the motivational and educational effect of a personalized follow-up by phone, Zoom, WhatsApp, or social networks.

To evaluate the implementation's effect on participants' quality of life. To evaluate the barriers and challenges to implementing the healthy life intervention.

The proposed indicators will make it possible to measure the effect of the proposed intervention on the exposome of the patients, as well as adherence to the intervention, through attendance at consultations and changes in lifestyle using validated questionnaires. Among the interventions, an individualized hybrid format is proposed, both with face-to-face consultations, as well as remote follow-up through telephone calls, video calls, or material sent through digital platforms, which will benefit patients who are far from the institute or who they have difficulties to attend due to travel times, work schedules; which translates into greater adherence to the intervention and positive changes in the lifestyle of patients. Finally, it is proposed to produce an educational manual and other printed or video support materials for patients, allowing the program to be replicated in other centers with similar needs in Mexico and Latin America. Additionally, the present study intends to use the variables obtained: the clinical, anthropometric, biochemical, inflammatory profile, and metabolites identified as possible biomarkers to develop a predictor algorithm for the deterioration of quality of life in patients.

Inclusion Criteria:

• Women diagnosed with stage I-III BC, confirmed by pathology and image at the INCAN
• Candidates for multidisciplinary treatment including surgery, chemotherapy, and/or hormonal treatments.
• Signed the informed consent form
• Have access to a mobile phone or any electronic device with an active internet connection to receive the program information.

Exclusion Criteria:

• Patients with inflammatory cancer
• Those with cardiomyopathy or ventricular dysfunction (NYHA >II), arrythmia secondary to left ventricular ejection alterations that requires medication, previous myocardial infarction, or angina pectoris in the last six months
• Receiving treatment for cardiovascular or cerebrovascular disease, inflammatory bowel disease, malabsorption syndrome, rheumatoid arthritis, lupus, thyroid diseases, or Cushing syndrome
• Unable to walk for at least 1 km
• Have cardiovascular, respiratory, or musculoskeletal diseases that impede physical activity
• Pregnant or breastfeeding
• Have psychiatric conditions impeding active participation in this protocol
• Do not understand Spanish