Despite it being one of the leading causes of cancer death among women, survival following a breast cancer diagnosis has greatly increased in high-income countries. However; this gave rise to a growing population of women living long after breast cancer with a diminished quality of life (QoL) due to the long-term effects of cancer and cancer treatment.

Exercise can improve QoL, fatigue, and other mental and physical health outcomes in this population, and is strongly recommended among breast cancer survivors, much like a healthy diet. However adherence in real-life to these recommendations is seldom satisfactory. Also, evidence regarding the effect and cost-effectiveness of concurrent healthy lifestyle behaviors compared to exercise alone is limited. Hence the need to develop pragmatic (evaluating the effectiveness of interventions in real-life conditions) theoretical-based customized interventions, which aim to improve uptake and instill long-term adherence of health lifestyle among breast cancer survivors.

ADA (Activité physique adaptée Doublée d'un Accompagnement spécifique post-cancer) is an integrative intervention based on physical activity, nutrition and supportive care. The interventions aims to improve breast cancer survivors' physical and mental health and instill long-term healthy behaviors.

Our study will be a pragmatic two-arm (ADA intervention versus control/usual care) cluster randomized controlled trial which examines the effectiveness of the ADA intervention program.

The primary endpoint will be health-related quality of life, as measured at 12-month after the start of the trial.

Several secondary outcomes will also be assessed; which include Physical activity level, relationship to food and self-efficacy.

The study aims to recruit 160 participants in total, divided into 20 activity groups (clusters) of 8 participants.

Primary analyses will be carried out on an intention to treat (ITT) basis, at both cluster and participant level. All statistical analysis will adjust for the clustering of patients within centers as a random effect.

The aim of this trial is to provide scientific evidence on the 'real-world' effectiveness of an easily generalizable trial, with clinically-significant outcomes, touching a growing number of cancer survivors.

Inclusion Criteria:

• adult women who are between 18 and 72 years of age
• had a diagnosis of localized breast cancer of any type, and who have completed their treatment (surgery, chemotherapy, radiotherapy) within the last 15 months, or still undergoing hormone therapy or nearing the end of their Herceptin treatment.
• French-speaking
• covered by the French Social Security system or benefiting from a similar health insurance system

Exclusion Criteria:

• A cancer diagnosis other than breast cancer, or a relapse/metastasis of breast cancer, or generalized cancer,
• A medical contraindication to exercise (a medical certificate of absence of contraindication to the practice of physical activity will be required, as for all physical activity in community settings).
• Significant visual or auditory problems or behavioral problems that make it difficult to participate in group physical activity sessions.
• a plan of moving away from the study site.
• participating in another clinical trial
• Male sex