There is strong evidence demonstrating the benefits that physical activity (PA) provides for patients with breast cancer (BC), both in prevention and throughout various treatments and in survivorship. However, there is still very limited information available regarding the level or amount of PA undertaken by BC patients or survivors. On the other hand, although there are general recommendations for physical exercise- 150-300 minutes per week of moderate activity or 75-150 minutes per week of vigorous activity-the type of physical exercise that is best at each stage of the disease, as well as adherence and preferences for different exercise programs, has not been thoroughly studied.

Physical exercise is a healthy, easily implemented and low-cost intervention that ought to be much more widely adopted among the BC population.

Understanding all these factors will help us better assess the degree of implementation and compliance with exercise programs in our population of BC patients. This diagnosis will be the first step towards establishing new strategies to improve patients' PA levels and their adherence to exercise programs, ultimately ensuring that these changes become consolidated as new lifestyle habits that provide our patients with a preventive factor against relapses, as well as a better quality of life.

According to data from the latest 2026 annual report by the Spanish Society of Medical Oncology (SEOM), breast cancer is the second leading cause of cancer worldwide (12.3% of cancer cases diagnosed in both sexes). The estimated number of new cases in Spain for 2021 is 38,318. In addition, men account for approximately 1% of all new diagnoses of this disease.

There is strong evidence of the benefits that physical activity (PA) brings to patients with breast cancer, both in prevention and throughout various treatments and survivorship. The latest review by the Physical Activity Guidelines Advisory Committee (PAGAC) in 2018 determined that there is currently robust evidence confirming that PA reduces the risk of developing seven types of cancer, including breast cancer, by between 10% and 24%.

Likewise, the American College of Sports Medicine (ACSM) in March 2018 concluded that there is strong evidence supporting an association between PA and the risk of developing several types of cancer, including breast cancer, as well as survival after the disease.

Evidence from several systematic reviews and meta-analyses shows a consistent inverse relationship between levels of PA after diagnosis and cancer-specific mortality (a 38% reduction) as well as all-cause mortality (a 48% reduction) among breast cancer survivors.

According to current PA guidelines, a minimum of 150-300 minutes per week of moderate activity or 75-150 minutes per week of vigorous activity is recommended. According to various studies, these recommendations are known by only a small percentage of breast cancer patients and survivors.

JUSTIFICATION Breast cancer patients who undergo chemotherapy and/or radiotherapy reduce their PA levels more than patients without adjuvant therapy or with hormonal treatment. There is still very little information providing data on the level or amount of PA undertaken by breast cancer patients or survivors. One of the first studies to objectively evaluate PA and sedentary levels using accelerometry in breast cancer survivors was conducted by Boyle et al. in 2015. Another study, carried out in Ohio with 227 participants, reported a recovery in activity levels from shortly after surgery up to one year later, followed by a reduction in PA five years after surgery. Regarding recreational activity levels, Mason et al. reported a low and relatively constant maintenance of these levels during five years of follow-up.

At the European level, a prospective cohort study in the Netherlands compared PA levels of women with breast cancer during and up to three years after treatment, with those of healthy women of similar age. The results showed that PA levels in women with breast cancer were lower, especially in women undergoing systemic treatment and in older women. From one to three years after diagnosis, women with breast cancer continued to have lower PA levels. In Belgium, a study with 267 breast cancer survivors demonstrated that PA levels decreased in the first year after surgery and remained below preoperative levels two years after the operation.

In Spain, a study involving 386 women evaluated PA levels in breast cancer survivors. The results indicated that most patients do not meet the recommended PA levels.

Regarding preferences on PA, a study conducted in Chile in 2018 with 112 breast cancer patients observed that, in general, patients preferred to exercise with other patients (76%), at moderate intensity (67%), performing different activities (94%), supervised (94%), with a fixed schedule (69%), and to do group activities (90%). Only 13% of patients met the exercise guidelines, and these were the youngest patients and those with a recent diagnosis. In Nova Scotia (Canada), Forbes et al. conducted a study in which it was found that 60% of breast cancer survivors preferred supervised or instructed activities and 53% preferred group sessions.

For all these reasons and given the lack of specific data on this population, it is considered essential to carry out the first study that provides information on the PA levels of breast cancer patients, as well as to determine socio-demographic differences and to identify preferences regarding exercise programs in this group of patients. In this way, it will be obtained a current diagnosis of these variables, serving as a starting point for designing new strategies to adapt current resources and improve adherence to PA.

Inclusion Criteria:

• Women and men.
• Individuals aged 18 years and over.
• Diagnosis of localized or advanced breast cancer, either undergoing treatment or in follow-up.
• Patients who are able and willing to complete the questionnaires provided for the study.

Patients with breast cancer at various stages of the disease. Patients access the questionnaire via a link that redirects them to the GEICAM intranet platform, where the questionnaire is hosted. The dissemination of the link is carried out through GEICAM's channels on social media, its website, and las newsletters de nuestros Asociados y a asociaciones de pacientes.

The dissemination of the link is conducted via GEICAM's channels on social media, GEICAM website, and newsletters for GEICAM members and patient associations.

The involvement of various national patient associations, with whom GEICAM has collaboration agreements, is expected to encourage the participation of as many patients as possible.