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Background: Atypical EGFR mutations occur in 10%-30% of non-small-cell lung cancer (NSCLC) patients with EGFR mutations and their sensitivity to classical epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKI) is highly heterogeneous. Patients harboring one group of uncommon, recurrent EGFR mutations (G719X, S768I, L861Q) respond to EGFR-TKI. Exon 20 insertions are mostly insensitive to EGFR-TKI but display sensitivity to exon 20 inhibitors. Clinical outcome data of patients with very rare point and compound mutations upon systemic treatments are still sparse to date.
Patients and methods: In this retrospective, multicenter study of the national Network Genomic Medicine (nNGM) in Germany, 856 NSCLC cases with atypical EGFR mutations including co-occurring mutations were reported from 12 centers. Clinical follow-up data after treatment with different EGFR-TKIs, chemotherapy and immune checkpoint inhibitors were available from 260 patients. Response to treatment was analyzed in three major groups: (i) uncommon mutations (G719X, S7681, L861Q and combinations), (ii) exon 20 insertions and (iii) very rare EGFR mutations (very rare single point mutations, compound mutations, exon 18 deletions, exon 19 insertions).
Results: Our study comprises the largest thus far reported real-world cohort of very rare EGFR single point and compound mutations treated with different systemic treatments. We validated higher efficacy of EGFR-TKI in comparison to chemotherapy in group 1 (uncommon), while most exon 20 insertions (group 2) were not EGFR-TKI responsive. In addition, we found TKI sensitivity of very rare point mutations (group 3) and of complex EGFR mutations containing exon 19 deletions or L858R mutations independent of the combination partner. Notably, treatment responses in group 3 (very rare) were highly heterogeneous. Co-occurring TP53 mutations exerted a non-significant trend for a detrimental effect on outcome in EGFR-TKI-treated patients in groups 2 and 3 but not in group 1.
Conclusions: Based on our findings, we propose a novel nNGM classification of atypical EGFR mutations.
Introduction: Cancer patients tend to prefer oral instead of parenteral chemotherapy. To date, there is little evidence on the medication adherence in cancer patients. We investigated medication adherence to tyrosine kinase inhibitors in patients suffering from non-small cell lung cancer. Methods: Tyrosine kinase inhibitor adherence was measured electronically by MEMS® (medication event monitoring system) over at least six months. Adherence rates were calculated in terms of Dosing Compliance, Timing Compliance, Taking Compliance, and Drug Holidays. Patients were dichotomized as adherent when Dosing Compliance and Timing Compliance were ≥80%, Taking Compliance ranged between 90 and 110%, and <1 Drug Holiday was registered. Quality of life was assessed by two questionnaires (EORTC QLQ-C30 version 3.0, EORTC QLQ-LC13) at three time points. Adverse drug events were reported via patient diaries. Results: Out of 32 patients enrolled, data from 23 patients were evaluable. Median Dosing Compliance, Taking Compliance, and Timing Compliance adherence rates of tyrosine kinase inhibitor intake amounted to 100%, 98%, and 99%, respectively; Drug Holidays were observed in three patients. Four patients were dichotomized as non-adherent. Three of them had a twice-daily tyrosine kinase inhibitor regimen. Median quality of life scores amounted to 67 (max. 100) and remained unchanged over the study period. Fatigue and rash were the most frequently reported adverse drug events. Conclusion: Medication adherence of non-small cell lung cancer patients treated with tyrosine kinase inhibitors was extraordinarily high and is likely to support the effectiveness of tyrosine kinase inhibitor treatment and a good quality of life over a long period of time. Adherence facilitating information and education is especially relevant for patients taking tyrosine kinase inhibitors in a twice-daily regimen.