From Cherry Picking to R1vasc, Clusters and Compass Points: Evolution, Technique, and Results of Parenchymal-sparing One Stage Hepatectomy for Multiple Colorectal Liver Metastases.

Objective: Evaluate the technical development and long-term outcomes of Parenchymal-sparing One-Stage Hepatectomy (POSH) for colorectal liver metastases (CLM).

Summary Background Data: For multiple bilobar CLM, two-stage hepatectomy (TSH) is suggested, with liver transplant proposed for unresectable cases. In this context, POSH showed effectiveness.

Methods: A prospective cohort of patients with ≥4 bilobar CLM (2004-2023) was analyzed using an intention-to-treat approach. POSH patients were classified by surgical margin. The primary endpoint was the technique evolution in terms of complexity, feasibility and indications; secondary endpoints included POSH oncological validity, safety, and survival.

Results: Of 407 patients, 388 underwent POSH, 17 TSH. Resection area-to-tumor number ratio improved from 0.67 (2004-2007) to 0.41 (2020-2023, P=0.024), eliminating TSH after 207 POSH cases. Among POSH cases: 105 (27.4%) were R0, 153 (39.9%) R1p (tumor-parenchymal exposure), 37 (9.7%) R1v (tumor-vessel detachment), and 88 (23.0%) R1vp (vascular/parenchymal exposure). R1v had outcomes comparable to R0, while R1p had worse OS, RFS, and local recurrence (P<0.05). R1vp showed intermediate outcomes. Tumor size (HR 1.071, P=0.002), primary tumor nodal status (HR 1.695, P=0.005), and R1p margin (HR 1.481, P=0.024) predicted OS. Major complications occurred in 9.3%, 90-day mortality was 0.8%. Redo-hepatectomy was feasible in 93 of 122 (76.2%) patients with intrahepatic recurrence, providing a significant 5-year OS benefit.

Conclusions: POSH is effective for bilobar CLM. Advancements in tumor clustering eliminated the need for TSH even in complex cases. R1v outcomes confirm the validity of vascular detachment.