Table 1. T790M detection with ctDNA and re-biopsy before and after afatinib treatment, and response to afatinib.

Patient*	T790M in ctDNA at PD under previous EGFR-TKI	T790M in ctDNA just before afatinib	Response to afatinib			T790M detection at PD under afatinib
			ORR	PFS (days)	Duration of treatment (days)	ctDNA	Re-biopsy
1		Negative	PR	575	592	Negative	Negative
2		Negative	PR	120	154	Negative	NE
3		Negative	PR	193	568	Negative	NE
4		Negative	PR	264	362	Negative	NE
5		Negative	SD	358	600	Positive (310)	Positive (274)
6		Negative	SD	88	92	Negative	NE
7		Negative	SD	211	339	Negative	NE
8	Negative	Positive (26.0)	PR	493	566	Positive (24.8)	Negative
9	Positive (25.4) †	Negative	PR	165	206	Positive (15.9)	NE
10	NE	Positive (24.1)	SD	328	609	Positive (22.4)	Positive (268)
11	NE	Positive (11.9)	SD	89	160	Positive (123)	Positive (325)
12	Negative	Negative	SD	98	159	Positive (8.7)	NE
13	Negative	Negative	SD	75	210	Positive (23.9)	NE
14	Positive (22.6)	Negative	SD	131	227	Negative	Positive (147)
15	NE	Negative	SD	119	125	Negative	NE
16	Positive (35.3)	Positive (24.6)	PD	56	343	Positive (63.4)	LN:Positive (42.6)
							Liver: Negative
17	NE	Positive (8.1)	PD	14	54	Positive (67.0)	NE
18	Positive (15.9)	Negative	PD	90	177	Positive (204)	Positive (489)
19	Positive (15.9)	Negative	PD	34	NE	Negative	NE
20	Positive (8.7)	Negative	PD	45	NE	NE	NE

*Patients 1–7 were treated with afatinib as first-line treatment or after discontinuation of 1^st generation EGFR-TKI due to adverse effects. Patients 8–20 were treated with afatinib after acquired resistance to previous EGFR-TKI, as EGFR-TKI re-challenge.

^†Number in parentheses is area under mutation peak of T790M by the MBP-QP method.

Abbreviations: PR, partial response; SD, stable disease; PD, progressive disease

NE, not evaluated; ORR, overall response rate; PFS, progression-free survival