Background Therapeutic de-escalation in oncology is a key issue in palliative care in all cancer stages to increase patients’ rehabilitation. The current cancer policy encourages investing in techniques that allow treatment de-escalation to benefit patient quality of life. This is of major importance for older cancer patients who often have comorbidities and limited life expectancy. Whole breast radiotherapy (WBRT), partial breast irradiation (PBI), and omission of radiotherapy (OR) are therapeutic options in women over 65 years with early breast cancer (EBC). In this context, therapeutic de-escalation must be strongly associated with patients receiving sufficient information. An encounter decision aid can help physicians to involve patients in treatment decision-making. Methods We aimed to implement an option grid for older women with EBC receiving radiotherapy treatment in France. This tool was developed from a qualitative exploratory study in order to identify information involved in the patient decision-making process. We initiated three methods of data collection: (1) Personal interviews and focus groups were both conducted with women 65 years or over who had received WBRT or Partial Breast Irradiation for EBC. (2) At the same time, telephone interviews were carried out with physicians. (3) A narrative literature review was performed. The option grid was organized by information needs in accordance with the priorities identified. Results 36 women with EBC and 22 physicians took part in the interviews. Major information needs emerging from the data collected were organised into five categories related to side effects, quality of life, medical techniques used, psychological consequences and cost. In addition, 15 specific elements that influence patient decision toward treatment options were identified from the literature, such as religious beliefs, Trust in physicians, and fear of radiation. Based on these results, the option grid was created to include 16 topics including side effects associated to interventions, irradiation techniques, cancer recurrence, and cost. Conclusions From 2020 to 2022, interventional research has been scheduled to evaluate the implementation of this option grid.