Abstract PO4-22-12: Robot-assisted nipple-sparing mastectomy using da Vinci SP single-port system: primary results from the pilot trial RASPIM-01

Abstract Background Robot-assisted breast surgery was developed in 2014 for nipple-sparing mastectomy through a concealable lateral chest wall incision smaller. Although successful experiences have been reported using a multi-arm surgical robotic system, collisions between robotic arms and instruments often result in the discontinuation of console workflow and limit the performance of the surgical robot. Compared to multi-armed robot systems, the SP system is single-armed, equipped with flexible instruments containing multiple joints that may avoid instrument collision, a controllable camera reducing visual dead spots, and a designated non-third-party port that allows single-port entry and full deployment of the instrument. The RASPIM-01 trial (NCT05448963) is a single-armed pilot study assessing the feasibility of robot-assisted nipple-sparing mastectomy (NSM) using a new SP system. Method This study is a pilot trial conducted in a single-arm, non-randomized design with a recruitment of 30 participants. The SP surgical robot is used in NSM through the lateral chest wall incisions. The major inclusion criteria are 1) Breast cancer with preoperative clinical tumor sizes less than 5 cm, with an adequate tumor-skin distance of at least 3mm, and without nipple-areolar involvement in at least 1cm around the nipple by image, 2) Breast cancer up to clinical stage IIIA (T3, N1-2) showing adequate response to neoadjuvant therapy and meeting criteria 1), 3) Germline pathogenic/likely pathogenic BRCA1 or 2 variant carriers with or without a breast cancer diagnosis, requiring unilateral or bilateral therapeutic mastectomy or prophylactic mastectomy. Exclusion criteria include extensive breast skin or nipple involvement such as inflammatory breast cancer, Paget’s disease, nipple discharge associated with malignancy, image suggestive of cancer involvement of the nipple and subareolar tissue, and stage III breast cancer without response to neoadjuvant therapy, and previous radiotherapy of the surgical side breast. The endpoint measurements include Primary endpoint: The ability to complete nipple-sparing mastectomy with an SP system in the per-protocol population without additional assistant port or conversion to open surgery. Statistical analysis includes point estimation with a 95% confidence interval to analyze the mean or proportion of key performance parameters. No interim analysis will be performed due to the limited number intended to recruit. Results The study recruited 30 breast cancer patients and conducted 30 NSMs, while no prophylactic mastectomy case was recruited. The median age was 44 years old, BMI was 22.4 (18.9-30.0) kg/m2. Median tumor size was 3.0 (1.0-14.6) cm, and axillary lymph node metastases were present in 7 cases (23.3%). T2 (13 cases, 43.3%) tumors were the majority, followed by Tis (10 cases, 33.3%), T1 (5 cases, 16.7%), and T3 (2 cases, 6.7%). The anatomical stages of invasive cancer were Ia (16.7%), IIa (26.7%), IIb (16.7%), and IIIa (6.7%), among them 9 (30.3%) received neoadjuvant chemotherapy before surgery. All NSMs met the primary endpoint of successful completion using the SP robot system without conversion to open mastectomy or the addition of an assistant port. Median console time was 108.5 (73-285) min and docking time was 2.5 (1-9) min. Specimen weight was 311.6 (107-838) gm, while 2 (6.7%) cases had their nipple excised due to cancer-involved margin reported from the frozen section. Twenty-six (86.6%) cases received autologous free flap reconstruction, among which 25 (83.3%) cases received DIEP, and 1 (3.3%) received PAP reconstruction. Four cases received implant (2 cases, 6.7%) or tissue expander (3 cases, 6.7%). Conclusion This is the first NSM clinical trial operated with SP surgical robot system and met its primary endpoint showing the feasibility to conduct NSM. Secondary and exploratory endpoints data will be reported after the completion of clinical follow-ups. Citation Format: Wen-Ling Kuo, Chia-Huei Chu, Jung-ju Huang. Robot-assisted nipple-sparing mastectomy using da Vinci SP single-port system: primary results from the pilot trial RASPIM-01 abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-22-12.