Microwave ablation for treating liver metastases

A randomised controlled trial of 30 patients with multiple colorectal liver metastases reported that the 1‑year, 2‑year and 3‑year survival rates were 71%, 57% and 14% respectively in patients treated by microwave ablation (MWA), and 69%, 56% and 23% respectively in patients treated by liver resection. Mean overall survival was 27 months in patients treated by MWA and 25 months in patients treated by liver resection (p=0.83); mean disease‑free survival was 11 months and 13 months respectively (p=0.47). A non‑randomised comparative study of 89 patients treated by MWA (n=35) or radiofrequency ablation (RFA; n=54) reported overall survival rates at follow‑up of 1, 2, 3 and 5 years of 82%, 67%, 56% and 44% respectively for MWA and 87%, 55%, 44% and 32% respectively for RFA (no significant difference between groups).

A retrospective comparative study of 81 patients (20 patients treated by MWA with or without local resection, 36 patients treated by liver resection, and 25 patients treated palliatively) reported 4‑year survival rates of 41% in the whole MWA group, 70% in the liver resection group and 4% in the palliative treatment group (significant survival benefit reported in patients treated by MWA compared with the palliative treatment group). The same study reported that 50% (10 of 20) of patients treated by MWA were still alive at a median follow‑up of 30 months and 25% (5 of 20) were disease‑free. A non‑randomised controlled study of 53 patients with liver metastases reported overall survival rates at follow‑up of 1 year, 3 years and 5 years of 80%, 51% and 17% in patients treated by MWA plus resection and of 87%, 49% and 44% in patients treated by resection alone (p=0.43 for the overall comparison). Disease‑free survival was 33% at 1‑year follow‑up and 17% at 3 years in the MWA plus resection group, and 26% at 1 year and 11% at 3 years in the patients treated by resection alone (p=0.54 for the overall comparison).

A case series of 450 patients with primary or metastatic liver tumours reported overall survival rates at follow‑up of 3 years and 5 years of 45% and 17% respectively in patients with colorectal liver metastases, of 70% and 54% in patients with neuroendocrine liver metastases, and of 48% and 23% in the patients with other liver metastases. The same study also reported median overall survival of 32 months in patients with colorectal liver metastases, 92 months in patients with neuroendocrine liver metastases and 25 months in patients with other liver metastases.

A retrospective matched‑cohort comparative study of 134 patients treated by MWA (n=67) or RFA (n=67) reported recurrence rates at the site of ablation of 6% in the MWA group at a median follow‑up of 18 months and 20% in the RFA group at a median follow‑up of 31 months (p<0.001). The same study reported ablation-site recurrence rates at 2‑year follow‑up of 7% for MWA and 18% for RFA (p=0.01).

The non‑randomised comparative study of 89 patients reported local recurrence in 9% (3 of 35) of patients in the MWA group and in 20% (11 of 54) of patients in the RFA group at a mean follow‑up of 32 months (p=0.072). Distant recurrence (defined by the presence of intrahepatic new tumour nodules) was reported in 43% (15 of 35) of patients in the MWA group and in 56% (30 of 54) of patients in the RFA group (p=0.242).

In the non‑randomised controlled study of 53 patients, there was no significant difference in hepatic recurrence‑free survival between the patients treated by MWA plus resection and the patients treated by resection only; rates were 56% at 1‑year follow‑up and 39% at 3 years and 5 years in the MWA plus resection group, and 55%, 42% and 35% respectively in the resection‑only group (p=0.86 for the overall comparison). The matched‑cohort comparative study of 19 patients reported local recurrence in 1 patient out of 6 treated by MWA and in none treated by RFA (no further details provided).

The case series of 450 patients (334 procedures for liver metastases) reported local recurrence in 5% (34 of 680) of completely ablated lesions. The same study reported median recurrence‑free survival lengths of 24 months in patients with colorectal liver metastases, 33 months in patients with neuroendocrine liver metastases and 25 months in patients with other liver metastases. Recurrence‑free survival rates at 3‑year and 5‑year follow‑up were 34% and 9% respectively in patients with colorectal liver metastases, 36% and 11% in patients with neuroendocrine liver metastases, and 31% and 9% in patients with other liver metastases.

The non‑randomised comparative study of 89 patients reported complete ablation rates at 1 month after the procedure in 94% (58 of 62) of tumours in the MWA group and in 84% (59 of 70) of tumours in the RFA group (p=0.094). A prospective case series of 1,249 patients with primary or metastatic liver tumours (307 with liver metastases) reported local tumour progression rates of 10% at 1‑year follow‑up, 15% at 2 years and 17% at 3 years; 73% (20 of 27) occurred within 1 year, 24% (6 of 27) between 1 and 2 years and 1 developed after 2 years.

Specialists advisers listed key efficacy outcomes as overall survival, progression‑free survival, rates of local recurrence, control of primary tumour (residual tumour rate defined as absence of any tumour on first post‑procedure imaging), and tumour response as assessed by Response Evaluation Criteria in Solid Tumours (RECIST) criteria.