Efficacy of third-generation epidermal growth factor receptor-tyrosine kinase inhibitors in advanced NSCLC with different T790M statuses tested via digital droplet polymerase chain reaction ddPCR and next-generation sequencing

Figures & data

Table 1. Demographic features of all enrolled EGFR-mutant NSCLC patients progressed from first-/second generation TKIs and received third-generation TKIs based on genetic results via ddPCR and NGS.

Characteristics	n	%
Age (Median/IQR)
Gender
Male	16	40.0
Female	24	60.0
Smoking status
Current/former	11	27.5
Never	29	72.5
ECOG-PS
0	24	60.0
1	14	35.0
2	2	5.0
EGFR mutation at diagnosis
Exon 19 deletion	20	50.0
Exon 21 mutation (L858R)	17	42.5
Exon 18 mutation	3	7.5
EGFR mutation retained at progression
Present	23	57.5
Absent	17	42.5
Coexistance of EGFR sensitive mutation at progression via NGS
Present	25	62.5
Exon 19 deletion	15	37.5
Exon 21 L858R	10	25.0
Absent	15	37.5
T790M status at progression
Positive via NGS (Group A)	12	30.0
Negative via NGS	28	70.0
Positive by ddPCR (Group B)	11	39.3*
Negative by ddPCR (Group C)	17	60.7*
Previous TKI treatment
First-generation TKIs	26	65.0
Second-generation TKIs	14	35.0
Duration on initial EGFR-TKIs (median, range)	16.3 months	3.8–77.2 months
Metastatic mode of previous TKI treatment
Intracranial metastases only	11	27.5
Extracranial metastases only	29	72.5
BOR to prior EGFR-TKI
CR/PR	20	50.0
SD/PD	9	22.5
No measurable lesions	11	27.5
Lines of prior systemic therapy
1	31	77.5
2	7	17.5
3	2	5.0
Brain metastasis prior to third-generation TKI
Present	14	35.0
Absent	26	65.0
Third-generation regimen
Osimertinib	35	87.5
Aumolertinib	3	7.5
Furmonertinib	2	5.0

n, number; IQR, interquartile range.

*The percentage of patients with or without the T790M mutation via ddPCR in those who were T790M-negative via NGS (n = 28).

The percentages might not equal 100% on account of rounding.

Figure 1. The flowchart and the categorization of all advanced NSCLC patients with EGFR-sensitizing mutations included for analysis of the efficacy of subsequent third-generation TKIs based on different statuses of T790M mutation.

Figure 2. Survival analysis based on T790M status via liquid biopsy prior to subsequent third-generation EGFR-TKIs, which was categorized as follows: group A, T790M-positive via NGS (n=12); group B, T790M-negative via NGS, while tested positive via ddPCR (n=11); group C, T790M-negative via NGS/ddPCR (n=17). (a) survival analysis in patients with T790M-positive and -negative via NGS; (b) survival analysis in group A, B, and C.

Figure 3. Survival analysis based on coexistance of EGFR sensitive mutation via NGS prior to subsequent third-generation EGFR-TKIs. (a) survival analysis in T790M-negative patients tested via NGS; (b) survival analysis in patients with T790M-negative tested via NGS while positive via ddPCR (group B).

Figure 4. A typical example in an advanced NSCLC patient successfully treated with osimertinib 80mg QD, subsequent to first-line gefitinib treatment and second-line therapy. This patients had a negative EGFR or T790M mutation status prior to third-line osimertinib via NGS in peripheral blood, while tested T790M-positive (0.03%) in a further ddPCR test using ctDNA.

(a) The CT scan of primary lesion at the right lung at baseline. The metastatic sites included multiple lesions in each lung.

(b) The CT scan of primary lesion at the right lung after first-line gefitinib. The patient has achieved a partial response per RECIST 1.1, with a shrinkage rate of 30.5% in the targeted lesion.

(c) The CT scan of primary lesion at the right lung at progression of first-line TKI. Progression disease occurred in the primary lesion, and gene test via NGS in peripheral blood indicated no mutations in EGFR.

(d) The CT scan of primary lesion at the right lung at progression of combining gefitinib and bevacizumab as second-line treatment for 2 cycles. Another gene test via NGS and ddPCR in ctDNA was conducted concurrently. The NGS testing was negative, while the ddPCT testing showed a positive T790M status (0.03%). The patients then received osimertinib as third-line treatment based on the genetic results.

(e) The CT scan of primary lesion at the right lung after third-line osimertinib treatment. The patient had a partial response per RECIST 1.1, with a shrinkage size in the primary tumor and the metastatic lesions in both lungs. The duration of response has been 13months until last follow-up at September, 2022.

Table 2. The overall best response to third-generation TKIs in 32 included patients with at least one target lesion.

Overall best response	N (%) All patients (n=32)	N (%) Group A (n=11)	N (%) Group B (n=7)	N (%) Group C (n=14)
CR	0 (0.0)	0 (0.0)	0 (0.0)	0 (0.0)
PR	8 (25.0)	4 (36.4)	2 (28.6)	2 (14.3)
SD	17 (53.1)	7 (63.6)	4 (57.1)	6 (42.9)
PD	7 (21.9)	0 (0.0)	1 (14.3)	6 (42.9)
ORR	8 (25.0)	4 (36.4)	2 (28.6)	2 (12.5)
DCR	25 (78.1)	11 (100.0)	6 (85.7)	8 (57.1)

n, number.

Table 3. The overall best response to third-generation TKIs in T790M-negative patients via NGS with at least one measurable lesion.

Overall best response	N (%)All T790M- patients (n=21)	N (%)Patients with EGFR sensitive co-mutations (n=7)	N (%)Patients without EGFR sensitive co-mutations (n=14)	P value
CR	0 (0.0)	0 (0.0)	0 (0.0)	-
PR	4 (19.0)	0 (0.0)	4 (28.6)	-
SD	10 (47.6)	2 (28.6)	8 (57.1)	-
PD	7 (33.3)	5 (71.4)	2 (14.3)	-
ORR	4 (19.0)	0 (0.0)	2 (28.6)	0.326
DCR	14 (66.7)	2 (28.6)	12 (71.4)	0.033

n, number.