Safety and Short-term Outcomes of Modular Robotic System for Siewert II/III Gastroesophageal Junction Cancer (ROBOT-GEJ)

Siewert type II/III gastroesophageal junction (GEJ) adenocarcinoma represents a unique clinical entity located at the junction between the distal esophagus and proximal stomach. According to the Siewert classification, type II tumors are defined as tumors with their epicenter located from 1 cm above to 2 cm below the esophagogastric junction, whereas type III tumors extend from 2 cm to 5 cm below the junction. Due to their distinct anatomical characteristics and lymphatic drainage patterns, these tumors present unique challenges in surgical management.

Siewert type II tumors have a relatively increased risk of mediastinal lymph node metastasis, while Siewert type III tumors primarily involve abdominal lymphatic pathways. Consequently, significant controversy remains regarding the optimal surgical approach, including the choice between transthoracic and transabdominal approaches, esophagectomy versus gastrectomy, and the appropriate extent of lymphadenectomy. In particular, the management of Siewert type II tumors remains debated because of their overlapping features between esophageal and gastric cancers. Currently, Siewert type III tumors are generally treated according to gastric cancer principles, with total gastrectomy and D2 lymphadenectomy being widely accepted surgical strategies.

Minimally invasive surgery has increasingly been applied in GEJ cancer treatment. Previous studies have demonstrated that laparoscopic surgery may provide advantages in reducing surgical trauma and improving short-term postoperative recovery compared with open surgery. However, existing evidence is primarily derived from retrospective studies, with considerable heterogeneity and limited long-term oncological outcome data.

Robotic-assisted surgery has emerged as an advanced minimally invasive approach, offering three-dimensional visualization, enhanced instrument dexterity, motion scaling, and improved ergonomics. Small retrospective series using the da Vinci integrated robotic platform for Siewert type II/III GEJ cancer surgery have demonstrated acceptable perioperative safety and feasibility. However, conventional integrated robotic systems have limitations in complex procedures requiring extensive operative fields. Due to restricted robotic arm mobility and fixed configuration, procedures involving both thoracic and abdominal regions may require intraoperative redocking, which may interrupt surgical workflow, prolong operative time, and reduce procedural efficiency.

The split-type robotic surgical system provides an alternative robotic platform design consisting of multiple independently movable robotic carts. This configuration allows more flexible arrangement of robotic arms according to surgical requirements and may be particularly advantageous for Siewert type II/III GEJ cancer surgery, where both mediastinal and abdominal lymph node dissection may be required. Compared with integrated robotic systems, split-type robotic platforms may reduce the need for intraoperative redocking, maintain procedural continuity, decrease mechanical interference, and improve surgical efficiency during complex multi-quadrant operations.

The Carina™ Split-type Surgical Robotic System and compatible surgical instruments developed by Ruilong Nuofu (Shanghai) Medical Technology Co., Ltd. have obtained approval from the National Medical Products Administration (NMPA) of China. The system has fulfilled regulatory requirements for investigator-initiated clinical studies according to relevant medical device regulations and clinical trial quality management principles. Previous clinical applications of the Carina™ system in multiple surgical specialties, including gastrointestinal surgery, have demonstrated acceptable safety profiles and perioperative outcomes.

Nevertheless, despite these theoretical advantages, clinical evidence regarding the application of split-type robotic systems in radical surgery for Siewert type II/III GEJ cancer remains lacking. In particular, whether split-type robotic surgery can improve operative efficiency, facilitate lymph node dissection, reduce surgical interruptions, and maintain acceptable perioperative safety has not been prospectively evaluated.

Therefore, this prospective single-arm clinical study is designed to investigate the feasibility, safety, and short-term outcomes of split-type robotic radical surgery for patients with Siewert type II/III GEJ adenocarcinoma. The study will evaluate perioperative parameters, including operative time, intraoperative blood loss, conversion rate, postoperative complications, recovery indicators, pathological outcomes, and lymph node dissection results.

The results of this study will provide preliminary clinical evidence regarding the role of split-type robotic technology in complex GEJ cancer surgery. These findings may serve as a foundation for future multicenter clinical trials, optimization of robotic surgical strategies, establishment of standardized surgical protocols, and improvement of clinical outcomes for patients with Siewert type II/III GEJ adenocarcinoma.