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MA21 - Non EGFR/MET Targeted Therapies (ID 153)
- Event: WCLC 2019
- Type: Mini Oral Session
- Track: Targeted Therapy
- Presentations: 1
- Now Available
MA21.09 - Tyrosine Kinase Inhibitors' Plasma Concentration and Oncogene-Addicted Advanced Non-Small Lung Cancer (aNSCLC) Resistance (Now Available) (ID 830)
14:30 - 16:00 | Author(s): ANGELO Paci
The development of TKIs against driver molecular alteration has changed treatment paradigm in aNSCLC patients (pts). All tumors eventually progress and a resistance mechanism is identified in only a fraction of pts. Plasma concentration of TKI can decrease after chronic exposition but limited data are available. Our hypothesis is that an insufficient plasma exposure could contribute to tumor progression (PD).Method
We assessed the plasma concentration of TKI in pts with aNSCLC harboring ALK rearrangement, EGFR or BRAF V600E mutation. We defined chronic exposure as a treatment administered > 3 months. Patients’ characteristics and co-medications were collected. Residual plasma concentrations were measured using Ultra Performance Liquid Chromatography coupled with tandem mass spectrometry validated methods. We compared results to currently recommended therapeutic targets and correlated exposure levels to treatment benefit.
Between Apr. 2014 and Feb. 2019, 51 samples were prospectively collected (gefitinib n=11, osimertinib n=10, erlotinib n=13, crizotinib n=7, dabrafenib + trametinib n=5) in 41 pts. Median time of exposure was 20.3 months (range 2.18 - 67.813). Low plasma concentration was observed in 31 (61%) samples. Out of 14 samples collected in pts with ongoing benefit, 10 (71%) had low plasma exposure. Smoking status was associated with low plasma TKI concentration (P=0.01) whatever the TKI used. A total of 37 samples were collected at PD, 21 (57%) had low plasma exposure. The median time to treatment failure (TTF) in the ‘low exposure group' (n=31) was 14.9 months (95% CI 12.48 – 33.2) vs. 24.6 months (95% CI 8.65 -not reached (NR) in the ‘normal exposure group’ (P=0.55). No significant impact of protons pump inhibitors on TTF was found (p=0.12), including with gefitinib and erlotinib (p=0.76; n=24). In case of isolated brain PD (n=4), 3 pts (75%) had low plasma exposure. TKI dose was reduced in 14 pts because of toxicity, median TTF was 17.0 months (95% CI 10.4-NR) vs. 20.1 months (95% CI 10.4-59.8, P=0.45 in pts treated with standard dose. In the EGFR mutated aNSCLC population at PD (n=19), T790M resistance mutation was more frequent in the ‘normal exposure group’ (37.5%, n= 3/8,) than in the ‘low exposure group’ (9.1%, n=1/11), OR=0.13 95%CI (0.01-1.29), p=0.08.Conclusion
TKI is underdose in the majority of aNSCLC patients at PD. Low TKI concentration were more frequent in pts without tumor resitance mechanism. Altogether, it suggests that low TKI exposure might contribute to PD.
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