Efficacy of immune checkpoint inhibitors plus platinum-based chemotherapy as 1st line treatment for patients with non-small cell lung cancer harboring HER2 mutations: Results from LC-SCRUM-Asia

Highlights•ICIs plus chemotherapy prolonged the PFS in HER2-mutant NSCLC.•TMB was higher in the tumors harboring HER2 mutations compared to EGFR mutations.•The relatively high TMB might be involved in the prolongation of the PFS.AbstractIntroductionHER2 mutations are reported to occur in 2%–5% of all cases of non-small cell lung cancer (NSCLC). The clinical outcomes in patients with HER2-mutant NSCLC treated with immune checkpoint inhibitors (ICIs) plus platinum-based chemotherapy as 1st line treatment still remain unclear.MethodsUsing the large-scale clinico-genomic database of LC-SCRUM-Asia, the clinico-genomic characteristics and therapeutic outcomes of patients with HER2-mutant NSCLC were investigated.ResultsOf the 15,251 patients with NSCLC enrolled in the LC-SCRUM-Asia database, tumor HER2 mutations were detected in 402 patients (2.6 %). The most common subtype of HER2 mutations was exon 20 in-frame insertions (79 %), followed in frequency by mutations in the tyrosine kinase domain other than Exon20ins (10 %) and mutations in extracellular domains (7 %). NSCLCs harboring HER2 mutations showed a higher tumor mutation burden (TMB) as compared with NSCLCs harboring EGFR mutations or ALK fusions (median: 4.22 vs. 2.54 and 2.52 mutation per megabase, respectively). Of the 402 patients, 268 patients had received platinum-based chemotherapy with ICIs (Chemo-ICI, n = 95) or without ICI (Chemo-alone, n = 173) as 1st line treatment. The progression-free survival (PFS) was significantly longer in the Chemo-ICI group as compared with the Chemo-alone group (median 8.5 vs. 6.3 months; HR [95 %CI]: 0.66 [0.50–0.88]; P < 0.005). Multivariate analysis identified use of ICIs in addition to platinum-based chemotherapy as an independent favorable prognostic factor for PFS. There was no significant difference in the overall survival between the patients of the Chemo-ICI and Chemo-alone groups (median 31.1 vs. 23.3 months; HR [95 %CI]: 0.80 [0.57–1.12], P = 0.20).ConclusionsAddition of ICIs to platinum-based chemotherapy in 1st line treatment may improve the PFS in patients with HER2-mutant NSCLC. The relatively high TMB might be involved in the prolongation of the PFS in patients with HER2-mutant NSCLC receiving platinum-based chemotherapy with ICIs.