Outcomes of ultrasound-guided percutaneous ablation of >5 versus ≤ 5 colorectal liver metastases: a propensity score matching study.

Objectives: To investigate the effectiveness and safety of microwave ablation (MWA) in patients with 1-5 colorectal liver metastases (CRLM) versus those with 6-9 CRLM.

Methods: Data from patients with 1-9 CRLM, who underwent ultrasound (US)-guided percutaneous MWA between January 2018 and May 2023, were retrospectively analyzed. Propensity score matching (PSM) at a ratio of 1:2 was used to balance potential bias between the groups.

Results: Data from 264 patients were included in the analysis. After PSM, there were 43 and 75 patients in the CRLM >5 and ≤5 groups, respectively. Even with higher tumor burden and technical difficulty, there was no statistical difference in the local tumor progression (LTP)-free survival (LTPFS) between the groups (p > 0.05). Patients with an ablation margin (AM) ≤5 mm exhibited a significantly higher rate of LTP than those with AM >5 mm in both groups(p < 0.05). Patients with 6-9 CRLM experienced a higher incidence of intrahepatic recurrence (iHR) (p = 0.041) and shorter progression-free survival (PFS) at any site (p < 0.05). CRLM > 5 is an independent risk factor for poor PFS (p = 0.008). The minor complication rate was lower in the CRLM ≤ 5 group (p < 0.05) and the major complication rate showed no difference (p > 0.05).

Conclusions: When the number of CRLM was limited to 9, single-session MWA was feasible and safe for radical local treatment. An AM >5 mm was critical for local tumor control. Compared with patients with 1-5 CRLM, those with 6-9 CRLM experienced inferior PFS at any site, which mainly lies in more iHR.