Patient's Choice in the Reduction of Their Treatment in Women Over 65 Year With Breast Cancer

Standard treatment for women with early breast cancer (HR+, HER2-, T1N0) consists of the removal of the tumor from the breast by surgery with or without chemotherapy, followed by a whole-breast radiation therapy (usually one radiation treatment a day, five days a week, for 3 to 6 weeks)

In some cases, for elderly patients older than 65 years with other associated pathologies, therapeutic de-escalation might be proposed in order to reduce the radiation doses received. Two options can be considered:

* Intraoperative radiotherapy: radiation is delivered in a single dose directly to the tumor bed during the surgery.
* Radiotherapy omission

These three treatment options (whole-breast radiation therapy, Intraoperative radiotherapy or -Radiotherapy omission) have advantages and disadvantages. Intraoperative radiotherapy allows a targeted treatment and avoids several weeks of daily radiation. Radiotherapy omission prevents acute or late toxicities of the radiotherapy, as well as the constraints of daily travel over a period of 3 to 6 weeks.

The aim of this trial is to offer patients aged 65 and over with early breast cancer, after surgery, these three treatment options and to study the choice and experience of treatment by patients. This study will assess the reasons that prompted patients to choose one of the three treatment options, the impact of medical and personal characteristics on this choice and the experience of therapeutic de-escalation as well as its effects, in particular on the course of care.

This assessment will be carried out with self-administered questionnaires before and after the choice of treatment.

In addition, to standardize the information given to patients in order to support them in their treatment choice and promote patient involvement in treatment decision-making, an encounter decision aid will be available for the patients. This encounter will detail the advantages and disadvantages of the three treatment options and will help in discussions with the physicians to determine the best choice of treatment.

Current demographic trends lead to an increasing number of breast cancers among 70+ women. In this population, adjuvant whole-breast radiation therapy (WBRT) after breast conserving surgery has proven its advantage on local control, but does not improve survival. Some experts are thus advocating WBRT omission.

In this context of limited life expectancy and of frequent comorbidities, therapeutic de-escalation (DE) might be proposed. Two options of de-escalation have been considered: (1) omission of adjuvant breast irradiation and (2) limiting the breast irradiated volume through a single-dose targeted intraoperative radiotherapy (IORT). As each of the three options (standard WBRT, IORT or no irradiation at all) has significant harms and benefits, treatment decision-making should not rely on the physician's opinion only.

A recent study has shown that in this context older women desire information and have more agency and input in the decision-making process than prior literature would suggest. The impact of therapeutic de-escalation on objective indicators and on patient reported outcomes must be investigated in current clinical practice, as uncertainties and doubt are likely to affect the decision-making process. When there is no definitive evidence to favour a treatment decision, assessing the patients' values and preferences appear to be of great relevance and value. Thus, the impact of therapeutic de-escalation on objective indicators and on patient reported outcomes (PROs) and experience (PRE) must be investigated, as uncertainty is likely to affect the decision-making process. We therefore propose to study the women's choice and experience of de-escalation of radiotherapy.

An encounter decision aid will be used to standardize the information provided about the three options and their outcomes. A prospective multicentre study using self-administered questionnaires before and after treatment decision making will then examine:

* the patient's choice and the impact of medical and patients' characteristics on this choice,
* the reason for the therapeutic choice from the patient's point of view,
* the experience of DE (patient-reported outcomes), and its medical effects (including care trajectories).

This study will document the rate and reasons of DE choice among French elderly early breast cancer patients. The results should facilitate the physician's reasoning at the time of treatment decision, and will also help patients (and their relatives) become better informed of the potential consequences of their choices. Developing a patient decision aid might also promote higher quality choices and shared decision-making in this context.

Eligibility Criteria:
Inclusion Criteria:

1. Patient must have signed a written informed consent form prior to any study specific procedures; when the patient is physically unable to give their written consent, a trusted person of their choice, independent from the investigator or the sponsor can confirm in writing the patient's consent
2. Women ≥65 years of age
3. Eastern Cooperative Oncology Group (ECOG) performance status ≤2
4. Clinical stage I, newly diagnosed breast cancer; invasive unifocal HR+ HER2- T1N0 tumour, not lobular, without extensive intraductal component (EIC) (\<25% EIC on biopsy), without embolism on biopsy
5. Eligible to surgery
6. Eligible for both WBRT or IORT
7. Chemotherapy treatment is possible if needed
8. Able to respond to self-report questionnaires in French
9. Affiliated to Social security System

Exclusion Criteria:

1. Patient with recurrent breast cancer or inflammatory breast carcinoma
2. Absolute contra-indication to whole-breast irradiation as determined by the referring physician
3. Patient unable to comply with study obligations for geographic, social, or physical reasons, or who is unable to understand the purpose and procedures of the study
4. Patient enrolled in another therapeutic trial. Observational cohorts are accepted if the collection of data does not interfere with the current trial
5. Person deprived of their liberty or under protective custody or guardianship.