Analysis of circulating tumour DNA to identify patients with epidermal growth factor receptor-positive non-small cell lung cancer who might benefit from sequential tyrosine kinase inhibitor treatment.

BACKGROUND: Survival data support the use of first-line osimertinib as the standard of care for epidermal growth factor receptor (EGFR)-positive non-small cell lung cancer (NSCLC). However, it remains unclear whether upfront osimertinib is superior to sequential first- or second-generation tyrosine kinase inhibitors (TKIs) followed by osimertinib for all patients. It is impossible to predict which patients are at high risk of progression, and this constitutes a major limitation of the sequential TKI approach. PATIENTS AND METHODS: A total of 830 plasma samples from 228 patients with stage IV, EGFR-positive NSCLC who were treated with first-line TKIs were analysed by digital polymerase chain reaction (dPCR). RESULTS: The circulating tumour DNA (ctDNA) levels helped to identify patients with significantly improved survival rate, regardless of the treatment. Patients treated with first- or second-generation TKIs (N = 189) with EGFR mutations in plasma at a mutant allele frequency (MAF) <7% before treatment initiation (low-risk patients) or who were ctDNA negative after 3 or 6 months of treatment and with an MAF <7% at diagnosis (high responders) had two-thirds lower risk of death than patients in the opposite situation (adjusted hazard ratio [HR] = 0.38; 95% confidence interval [CI]: 0.23-0.64 and HR = 0.22; 95% CI: 0.12-0.42, respectively). The median overall survival (OS) for low-risk patients and high responders treated with first- or second-generation TKIs was 34.2 months and not reached, respectively, regardless of second-line treatment. There were no significant difference in OS between low-risk or high-responder patients treated upfront with osimertinib (N = 39) and those treated under a sequential approach with osimertinib (N = 60). Median OS was not reached in both cases. CONCLUSIONS: Pre-treatment ctDNA levels identify low-risk patients, who may benefit from sequential TKI treatment. Information regarding EGFR mutation clearance can help to improve patient selection.

Dynamic circulating tumor DNA quantificaton for the individualization of non-small-cell lung cancer patients treatment.

BACKGROUND: Liquid biopsy has evolved from being a promising line to becoming a validated approach for biomarker testing. However, its utility for individualization of therapy has been scarcely reported. In this study, we show how monitoring levels of EGFR mutation in plasma can be useful for the individualization of treatment. RESULTS: Longitudinal EGFR mutation levels in plasma always correlated with tumor response ascertained by RECIST criteria. Moreover, decreasing EGFR mutation levels were detected in all patients benefiting from locoregional radiotherapy, whereas the opposite occurred when a patient progressed soon after radiotherapy treatment. Similarly, increasing EGFR mutation levels anticipated disease progression after TKI dose reduction, discontinuation of treatment, or reduced bioavailability due to drug interactions. In addition, EGFR mutation levels were useful to monitor treatment outcome of new therapies and constituted a decisive factor when the clinical situation of the patient did not correlate with responses ascertained by radiologist. Finally, our results indicate that cancer associated body fluids (pleural, pericardial or cerebrospinal fluid) are certainly a suitable source for biomarker testing that can extend EGFR mutation detection to biofluids other than blood. MATERIALS AND METHODS: A total of 180 serial plasma samples from 18 non-small-cell lung cancer patients who carried an activating EGFR mutation were investigated by digital PCR. CONCLUSIONS: Monitoring levels of EGFR mutation in plasma allows resolving doubts that frequently arise in daily clinical practice and constitutes a major step towards achieving personalized medicine.