Breast-conserving surgery is the standard treatment for young breast cancer patients, while mastectomy with breast reconstruction is an alternative for those who are not eligible for Breast-conserving surgery. Several studies have compared the quality of life and patient satisfaction among individuals receiving different types of surgery (Breast-conserving surgery, mastectomy alone, or mastectomy with reconstruction). For example, Meghan R. demonstrated that patients undergoing Breast-conserving surgery experience a higher quality of life compared to those undergoing mastectomy with breast reconstruction, whereas J. Dauplat's study showed that patients who undergo mastectomy with breast reconstruction report a higher quality of life than those who undergo mastectomy alone.

However, the investigators hypothesize that the advantages of a specific type of surgery over another, such as Breast-conserving surgery versus breast reconstruction, may vary among patients with different socioeconomic factors. For instance, the benefits of breast reconstruction over Breast-conserving surgery might be more pronounced in young patients who require a more socially active lifestyle.

Additionally, the benefits of one type of surgery over another may also vary at different time points during post-operative follow-up. Furthermore, it is worth noting that most current studies have been conducted in Caucasian populations. In contrast to Caucasians, Asians typically have smaller breast volumes, potentially leading to more significant defects after Breast-conserving surgery and possibly poorer aesthetic outcomes. Therefore, a study focusing on Asian young breast cancer populations is necessary.

This study is a prospective, observational cohort study aiming to enroll 1000 young Chinese breast cancer patients and assign them to three arms: Breast-conserving surgery, mastectomy alone, and mastectomy with breast reconstruction, based on their clinical decisions and preferences. Clinicopathological features (age,Tumor, Node, Metastasis stages, pathological features, etc.), socioeconomic determinants (education level, income, insurance status, marital status, occupational status, personality, etc.), treatment information (neoadjuvant chemotherapy or not, post-operative complications), and survival (local recurrence, metastasis) will be recorded.

All patients will be followed at 6 and 12 months for the first year after diagnosis, then yearly thereafter for an additional 9 years (for a total follow-up of at least 10 years following diagnosis). During the post-operative follow-up, quality of life, psychological well-being, decision regret, surgical information, treatment costs, and surveillance-follow-up will be recorded.

The primary endpoint of this study is the quality of life, assessed using the Breast-Q and the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30). Secondary endpoints include decisional conflict scale, decision regret scales, and the Hospital Anxiety and Depression Scale (HADS).

The primary and secondary endpoints will be compared among the three arms, and the impact of socioeconomic determinants at baseline on these endpoints will also be investigated. Additionally, the investigators aim to explore the potential of a novel subtyping method for young breast cancer patients using selected socioeconomic determinants.

Inclusion Criteria:

• Age between 18 and 50 years old.
• The surgery time and procedure have been confirmed, and the surgical informed consent and research informed consent forms have been signed.
• Informed consent obtained from patient.
• Unilateral Breast Cancer.
• Good health,the patient is able to tolerate general anesthesia and surgery, with an ECOG performance status of ≤2 points.
• No history of breast/axillary radiation therapy.
• Willing and capable of complying with the study protocol visits, treatment plans, and other research procedures.

Exclusion Criteria:

• Bilateral breast cancer.
• Inflammatory breast cancer.
• Stage IV breast cancer.
• Physical examination and imaging suggest tumor infiltration into the skin, pectoralis major muscle, and other adjacent tissues.
• Patients unable to tolerate surgery due to coagulation abnormalities.
• In patients without evidence of breast cancer in the contralateral breast, requesting contralateral prophylactic mastectomy.
• In patients who have undergone surgical treatment for breast cancer (including mastectomy, breast-conserving surgery, and mastectomy with implant reconstruction), requesting secondary breast surgery.
• Patients with a history or current diagnosis of other malignancies, excluding thyroid cancer.
• The conditions considered unsuitable for inclusion by researchers.

Young breast cancer women.

The study protocol and the raw and clean data for analysis will be shared among the participated researchers. Non-researchers could obtain relevant informations from the researchers upon reasonable requests.