Microwave ablation: a better treatment alternative for NSCLC?

In patients with non-small-cell lung cancer (NSCLC), image-guided thermal ablation (IGTA) via microwave ablation (MWA) appears to deliver better survival benefit compared with another IGTA subtype, radiofrequency ablation (RFA), or stereotactic body radiation therapy (SBRT), according to a systematic review and meta-analysis presented at ATS 2022.

“SBRT and IGTA … are accepted alternate treatment options for primary NSCLC, especially for patients who are not eligible for or decline surgery,” said the researchers. “However, a comprehensive assessment of these treatments can be challenging, because of the lack of comparative evidence on outcomes after these treatments.”

“[In our analysis, despite similar] OS rates … between IGTA and SBRT, [there was] a trend towards higher OS rates for MWA vs both RFA and SBRT [in patients with primary NSCLC]. Similar results were observed in a subgroup of early-stage NSCLC patients,” said the researchers.

This systematic review of literature comprised studies on NSCLC patients who have received MWA, RFA, or SBRT (n=1,358, 1,522, and 53,305, respectively). An early-stage NSCLC subgroup (ie, those in stage IA, T1a, and T1b or with a mean/median tumour size of ≤2 cm) was also evaluated. Overall survival (OS) and progression-free survival (PFS) were evaluated at 1 year, 2 years, and 3 years. Local tumour progression (LTP) was assessed at 1 year and 2 years. [ATS 2022, abstract 316]

The pooled OS for MWA were 89, 84, and 69 percent at the respective 1-, 2-, and 3-year mark. The corresponding values were lower in the RFA (84, 65, and 50 percent) and SBRT cohorts (86, 69, and 57 percent).

Multivariable* regression analysis revealed no statistically significant differences in OS across all timepoints when MWA was compared against RFA (adjusted odds ratios [adjORs], 0.73, 0.68, and 0.48 at 1 year, 2 years, and 3 years, respectively) and SBRT (adjORs, 0.64, 0.61, and 0.73, respectively). A similar trend was seen between SBRT and overall IGTA (adjORs, 0.74, 0.74, and 1.06, respectively).

Barring the adjustments however, compared with MWA, RFA was associated with significantly lower OS across all timepoints (ORs, 0.52, 0.36, and 0.44 at 1 year, 2 years, and 3 years, respectively), as was SBRT at 2 years (OR, 0.44; p<0.05 for all). When comparing overall IGTA against SBRT, the differences were not statistically significant (ORs, 0.97, 0.89, and 0.98, respectively).

Early-stage NSCLC patients

In this patient subset, those who received MWA had higher OS estimates than those who received RFA at 2 years (90 percent vs 74 percent) and those who were treated with SBRT across all timepoints (96 vs 86 percent [1 year], 90 percent vs 71 percent [2 years], and 85 percent vs 59 percent [3 years]).

There were minimal differences between the four treatment arms (MWA, RFA, IGTA, and SBRT) in this subgroup in terms of PFS estimates, ranging between 81 and 89 percent at 1 year, 68 and 72 percent at 2 years, and 44 and 56 percent at 3 years.

LTP estimates were lower with MWA compared with RFA (4 percent vs 10 percent), but similar compared with SBRT (4 percent for both) at 1 year. By year 2, the estimates for MWA were lower for both comparisons (7 percent vs 17 percent [RFA] and 9 percent [SBRT]).

“[Taken together,] data from this [review] and meta-analysis support the clinical use of MWA as a local treatment strategy in NSCLC patients because of clinical equipoise between MWA, RFA, and SBRT for most outcomes and timepoints,” the researchers concluded.