The goal of this multi-center randomized controlled trial is to determine if the clinical decision aid (BCT Aid) works to help breast cancer patients participate in decision-making and make high-quality decisions, thereby improving the rate of breast-conserving surgery and quality of life. The main questions it aims to answer are:

Does the BCT Aid significantly increase the rate of breast-conserving surgery compared to usual care? Does the BCT Aid reduce decision conflict and decision regret, while improving shared decision-making and quality of life? Does the BCT Aid demonstrate better cost-effectiveness in terms of health resource utilization? Researchers will compare the BCT Aid to usual care (standard clinical consultation) to evaluate the effectiveness and cost-effectiveness of BCT Aid.

Participants will:

Be randomly assigned to either the intervention group (receiving the BCT Aid intervention for 6 months) or the control group (usual care).

Complete assessments including decision conflict and shared decision-making at baseline (T0), post-consultation with the surgeon (T1), 6 months (T2, post-intervention), and 12 months (T3, 6 months post-intervention), decision regret at T2 and T3, and quality of life at T0, T2, and T3, with additional EQ-5D-5L measurements at baseline, 3, 6, 9, and 12 months for cost-effectiveness analysis.

Have clinical outcomes (breast-conserving surgery rate) and health resource utilization data collected from medical records.

Breast cancer is one of the most common cancers among women in China. More than 90% of breast cancer patients undergo either modified radical mastectomy (mastectomy with or without reconstruction) or breast-conserving surgery (lumpectomy with radiation therapy), with no significant difference in survival outcomes between the two approaches for patients with early-stage breast cancer. The National Comprehensive Cancer Network (NCCN) Clinical Practice Guidelines for Breast Cancer recommend breast-conserving surgery as the preferred surgical option for early-stage breast cancer in the absence of clinical contraindications. However, while the breast-conserving surgery rate ranges from 56.4% to 64.5% in Western countries, it remains only 22% in China. Common reasons for the low rate of breast-conserving surgery in China include fear of cancer recurrence, limited healthcare resources, information asymmetry between patients and healthcare providers, and distrust toward breast-conserving surgery.

A preliminary study conducted by the research team found that patients undergoing breast-conserving surgery had significantly lower levels of decision conflict, decision regret, and stigma compared with those undergoing modified radical mastectomy, and these three factors together explained 32.6% of the variance in quality of life. In a further study by the same team, data from 1,592 breast cancer patients were collected from two hospitals affiliated with Xiamen University between 2009 and 2017, and these data were linked with mortality records from the Xiamen Center for Disease Control and Prevention. The results showed that patients who underwent modified radical mastectomy and breast-conserving surgery had similar survival rates, and endocrine therapy was associated with improved survival. Based on these findings, the research team developed a survival predict model for breast cancer.

The World Health Organization has proposed that breast cancer patients should be fully informed about their diagnosis and the risks and benefits of available treatment options, and should be involved in making clinical treatment decisions together with healthcare providers, taking into account their personal values and preferences. In recent years, awareness of shared decision-making has increased among breast cancer patients in China, but the actual level of patient participation remains lower than their desired level of involvement.

Decision Aids (DAs) are tools designed to facilitate shared decision-making between patients and healthcare providers, particularly in situations where multiple treatment options are available. Currently, there is a lack of accessible, continuous, and cost-effective DAs to support shared decision-making for breast cancer patients in China. Globally, few randomized controlled trials of web-based DAs have been conducted. Due to limitations such as small sample sizes, single-center designs, and inconsistent outcome measures, the effectiveness of breast cancer DAs remains inconclusive, with no reported cost-effectiveness analyses to date.

In this study, a decision aid (BCT Aid) for newly diagnosed breast cancer patients was developed based on the shared decision-making model, integrating a patient values module, , a survival predict module, and a information module. A multi-center, assessor-blind, randomized controlled trial will then be conducted at three hospitals (Women and Children's Hospital Affiliated to Xiamen University, the First Affiliated Hospital of Xiamen University, and Xiang'an Hospital Affiliated to Xiamen University) to evaluate the effectiveness of the BCT Aid and perform a cost-effectiveness analysis. If the trial demonstrates its effectiveness, the BCT Aid can be directly implemented in clinical practice. Patients can use the BCT Aid to access survival predictions for different treatment options, weigh the benefits and harms, and make better-informed clinical decisions. When physicians discuss surgical options with patients, they can input patient demographic information (e.g., age), clinical information (e.g., breast cancer stage and subtype), and different treatment options into the BCT Aid, which will present survival prediction for each option in a simple and intuitive graphical format. In the values module, patients' values and preferences will be clarified through human-computer interaction to help guide treatment recommendations. The BCT Aid is designed to support patient participation in and facilitate high-quality clinical decision-making.

Inclusion Criteria:

1. Age ≥ 18 years.
2. Newly diagnosed with breast cancer, with clinical stage 0-II, or stage III eligible for breast-conserving surgery after neoadjuvant chemotherapy.
3. Clinically eligible for breast-conserving surgery and considering one of the following surgical options: breast-conserving surgery, mastectomy, or mastectomy with reconstruction.
4. Clinically eligible for adjuvant therapy after surgery.
5. Able to access the internet via smartphone.
6. Able to read, speak, and understand Mandarin.

Exclusion Criteria:

1. Male breast cancer patients.
2. Clinically eligible for only one surgical option or not candidates for surgery.
3. Have a history of other malignancies, except adequately treated cervical carcinoma in situ and basal cell carcinoma of the skin.
4. Presence of psychiatric disorders, visual or hearing impairments, or cognitive impairment.

Sharing of individual participant data is not planned due to patient confidentiality concerns and institutional data protection policies.