Exploring the Upper Limit: The Added Value of Local Treatment in Patients with Multiple Colorectal Liver Metastases: An Amsterdam Colorectal Liver Met Registry (AmCORE)-Based Study

Purpose: Partial hepatectomy and thermal ablation are standard local treatments for patients with limited colorectal liver metastases (CRLM). However, as the number of metastases increases, the question arises whether local treatment is still biologically meaningful. This study evaluates the value of radical local treatment in patients with a higher number of CRLM and seeks to identify a potential threshold of diminishing benefit. Methods: Data from the prospective AmCORE Registry were used. Patients with CRLM were divided into five groups: systemic therapy alone, and local treatment for solitary, 2–4, 5–9, and ≥ 10 CRLMs. The primary outcome measure was overall survival (OS); secondary outcome measures included local- and distant progression-free survival (LTPFS, DPFS), local control (LC), length of hospital stay, complication rates, and total tumour volume. Results: Local treatment significantly improved OS compared to systemic therapy alone (p < 0.001), with no evidence of a threshold of diminishing benefit. There were no differences in OS between the local treatment groups over a median FU of 52.9 months (95% CI, 44.0–61.8). Median OS for the systemic therapy group was 17.9 months (95% CI, 14.1–21.6). Local treatment offered favourable LTPFS and LC per-tumour for multiple CRLM. Length of hospital stay and complication rates increased with the number of treated CRLM. Median tumour volume increased with higher numbers of CRLMs but decreased in the ≥ 10 CRLMs group (p = 0.12). Conclusion: No upper limit was identified for the number of CRLMs treated with curative intent resection and/or ablation. This study supports the safety and efficacy of local treatment for patients with high numbers of CRLMs.