Table 2.

Characteristics of patients with detected EGFR amplification.

Patient	Sample type	EGFR activating mutation	T790M status	Pre-existing/acquired EGFR amp	Other potential concomitant resistance mechanisms
2	P	21L858R	+	Acquired	−
9	P	Del19	+	Pre-existing	AXL amp#
16	P	Del19	+	Pre-existing	MET amp, EGFR C797S
18	P	Del19	+	Acquired	CDKN2A/2B del
20	P	21L858R	+	Pre-existing	PIK3CA E545K & SCLC
23	Ta & P	Del19	+	Pre-existing	−
24	CSFa & P	Del19	+	Unknown	CDKN2A del
26	T	Del19	+	Unknown	EGFR L718V
28	Ta & P	Del19	−	Unknown	MET amp
29	T	Del19	+	Acquired	−
30	T & P	Del19	+	Acquired	EGFR C797S#

21L858R, EGFR 21L858R mutation; CSF, cerebrospinal fluid; amp, amplification; Del19, EGFR 19 deletion; P, plasma; T, tissue; AXL amp#, EGFR copy number gain was observed upon RECIST disease progression, while AXL amp was detected upon clinical disease progression with further copy number gain of EGFR; EGFR C797S #, EGFR C797S mutation was detected only in plasma, while EGFR amp was detected in both tissue and plasma upon abivertinib progression in P30.

^aEGFR amp was identified in P23, P24, P28 by tissue or CSF, but not in plasma.