BackgroundKRAS is commonly mutated in non-small cell lung cancer (NSCLC); however, the prognostic and predictive impact of each G12 substitution has not been fully elucidated. The approval of specific G12C inhibitors has modified the idea of KRAS “undruggability”, and although the first-line standard consists of immune checkpoint inhibitors (ICIs) with or without chemotherapy, as suggested at ASCO 2022, the outcome in KRAS-mutated population is still controversial.MethodsWe retrospectively described the clinical and pathological characteristics of a homogeneous G12 mutated cohort of 219 patients treated in four Italian oncologic units. We evaluated the outcome (PFS at 18 months and OS at 30 months) of those who underwent standard first-line treatment according to PD-L1 status, focusing on differences across single mutations.ResultsIn the study population, 47.9% of patients harbor the KRAS G12C mutation; 20.5%, G12V; 17.4%, G12D; and 8.2%, G12A. Smoking was a common behavior of patients harboring transversions and transition mutations. PD-L1 expression does not show particular distribution in the case series, although we recorded a prevalence of PD-L1 <1% in G12V (51.4%) compared to G12A (26.7%). ICIs alone was the clinician’s choice in 32.7% of patients, and the chemo-immune combination in 17.3% of patients. We described the independent prognostic role of young age (p = 0.007), female gender (p = 0.016), and an ICI-based regimen (p = 0.034) regardless of mutations. Overall, our data confirm the worst prognostic value of G12V mutation apart from treatment choice unlike the other major mutations (C, D, and A) that showed a favorable trend in PFS.ConclusionsKRAS G12 mutations are confirmed to have different characteristics, and the outcome is influenced by ICI first-line regimen. This study provides valuable information for further analysis in the future.

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Treatment with immune checkpoint inhibitors (ICIs) that target the programmed cell death 1/programmed cell death ligand-1 (PD-1/PD-L1) axis is usually ineffective in patients with epidermal growth factor receptor (EGFR)-mutated advanced non-small cell lung cancer (NSCLC), either as first-line treatment or in later lines. By contrast, especially for patients with common EGFR mutations (exon 19 deletion/L858R point mutation), an orally bioavailable EGFR tyrosine kinase inhibitor (EGFR-TKI) is the best upfront therapy, being able to provide response rates well above 50% and a median progression-free survival ranging from 11 to 19 months, depending on whether a second-generation (e.g., afatinib) or a third-generation (i.e., osimertinib) EGFR-TKI is used. Unfortunately, treatment options for these patients at the time of acquired resistance are limited. As for afatinib-pretreated patients, those who develop a T790M mutation may benefit from osimertinib, whereas platinum-based chemotherapy is the preferable therapeutic strategy for T790M-negative patients as well as for patients who progress on osimertinib administered as first-line therapy. Here, we describe the case of an exon-19-deleted patient who experienced a complete response to the anti-PD-1 agent pembrolizumab upon the development of T790M-negative acquired resistance to afatinib. Furthermore, we discuss this case in the context of the existing literature, especially focusing on the importance of evaluating multiple markers of immune response post-EGFR-TKI and prior to ICI treatment in order to select the best treatment strategy in this clinical scenario.