Nipple-sparing mastectomy (NSM) is indicated for breast cancer requiring total mastectomy and without nipple involvement by cancer. Robot-assisted mastectomy enables removal of the whole breast tissue with well-preserved breast skin envelope through a single longitudinal incision in the anterior axillary line at the nipple areolar level. The next-generation robot, da Vinci SP system, is single-armed, equipped with multiple flexible instruments and camera, which is likely to improve the efficacy of robotic mastectomy. The investigator's scope of this study is to establish the feasibility and safety of SP-applied NSM through this single-armed pilot trial. Participants with breast cancer indicated for nipple-sparing mastectomy or candidates of prophylactic mastectomy carrying germline pathogenic or likely pathogenic BRCA1/2 mutations are recruited to receive SP-assisted unilateral or bilateral NSMs. Immediate breast reconstruction is followed according to the mode of the plastic surgeon's clinical decision. The primary endpoint is technical feasibility, and the secondary endpoint is safety and patient-reported outcome.

About 49% of breast cancer surgery is managed by total mastectomy, and half of the patients undergo breast reconstruction. Nipple-sparing mastectomy (NSM) is indicated for breast cancer requiring total mastectomy and without nipple involvement by cancer. The local recurrence rate is not increased and the cosmetic result much improved. Robot-assisted mastectomy utilizes surgeon-controlled robotic arms with delicate, multi-jointed instruments and 3-dimentional high-definition camera in place of conventional instruments under bare eye vision. Through a single longitudinal incision in the anterior axillary line at the nipple areolar level, the lesion and the whole breast tissue can be totally removed with negative resection margins and well-preserved breast skin envelope. Breast reconstruction can be successfully performed through the same incision and results in a scarless front view. Currently, this surgery is effectively carried out with da Vinci Xi system. However, the small incision may result in the collision of robotic arms outside the torso and hence decreases the range of instrument motion. The next-generation robot, da Vinci SP system, is single-armed, equipped with multiple flexible instruments and camera, which are devoid of outside collision and allows work in a larger surgical field through the same small incision. The SP system reduces blind areas in the surgical field and the blockade of camera vision by the detached space-taking specimens, and, therefore, will hopefully reduce the surgical time. The investigator's scope of this study is to establish the feasibility and safety of SP-applied NSM through this single-armed pilot trial. The investigators recruit breast cancer women indicated for nipple-sparing mastectomy or candidates of prophylactic mastectomy carrying germline pathogenic or likely pathogenic BRCA1/2 mutations to receive SP-assisted unilateral or bilateral NSMs. Immediate breast reconstruction is followed according to the mode of the plastic surgeon's clinical decision. The primary endpoint is technical feasibility (conversion rate, surgical time), and the secondary endpoint is safety and patient-reported outcome.

Inclusion Criteria:

• Women with unilateral or bilateral breast cancer, including invasive and noninvasive carcinoma, eligible for unilateral or bilateral nipple-sparing mastectomy (NSM), either for therapeutic or prophylactic purpose, followed by immediate breast reconstruction.

  1. Meet at least one of the following indications of NSM for breast cancer:

     1. Preoperative clinical tumor sizes less than 5 cm, with adequate tumor-skin distance of at least 3mm and above, and without nipple-areolar involvement in at least 1cm around the nipple by image
     2. Breast cancer up to stage IIIa (T3, N1-2) as the initial clinical stage showing adequate response to neoadjuvant therapy and meet criteria a.
     3. Germline pathogenic/likely pathogenic BRCA1 or 2 mutation carriers (actionable mutations including pathogenic and likely pathogenic mutations) with breast cancer diagnosis or requiring unilateral or bilateral prophylactic mastectomy as a risk reduction procedure

  2. Age equal to or above 20 years

  3. ECOG (Eastern Cooperative Oncology Group) performance score 0-1

  4. ASA anesthesia risk class 1~2, and with adequate organ functions

  5. Understanding of the method, benefit and risk and willing to receive immediate breast reconstruction

Exclusion Criteria:

1. Extensive breast skin or nipple involvement by cancer including 1) Paget's disease, 2) nipple discharge associated with malignancy, 3) image findings suggesting involvement of the nipple and subareolar tissues 4) inflammatory breast cancer or skin ulceration caused by cancer invasion
2. Stage III (up to T3, N1-2) breast cancer without response to neoadjuvant treatment
3. Previous radiotherapy on the surgical site of breast
4. Patients with severe systemic disease reaching ASA (American Society of Anesthesiologists) physical status classification equal or greater than 3
5. Patients with bleeding disorder or coagulopathy
6. Patients with BMI 35.0 or higher
7. Patients with habitual smoking
8. Pregnancy

IPD are to be shared upon request to the principle investigator. The content of data sharing depend on research relevance and cooperative detail.