Imatinib efficacy by tumor genotype in Korean patients with advanced gastrointestinal stromal tumors (GIST): The Korean GIST Study Group (KGSG) study

Figures & data

Table I. Patients’ characteristics and tumor genotypes (n = 290).

Characteristic	No.	%
Age (years)
Median	60
Range	24–82
Gender
Male	163	43.8
Female	127	56.2
ECOG Performance status
0–1	256	88.3
2–3	26	9.0
Unknown	8	2.8
Disease status at start of imatinib
Locally advanced unresectable	8	3.8
Metastatic	132	45.5
Recurrent	150	51.7
Primary tumor site
Stomach	100	34.5
Small intestine	152	52.4
Colorectum	20	6.9
Extra-gastrointestinal	13	4.5
Unknown	5	1.7
Metastatic site
Liver	175	60.3
Peritoneum	122	42.1
Lymph node	9	3.1
KIT mutation
Exon 11	222	76.6
Exon 9	35	12.1
Exon 13	2	0.7
Exon 17	2	0.7
PDGFRA mutation
Exon 12	1	0.3
Exon 14	0	0
Exon 18	3	1.0
No mutation (wild type)	25	8.6

ECOG, Eastern Cooperative Oncology Group.

Table II. Responses to imatinib 400 mg daily by genotype (n = 235).

	CR		PR		SD		PD
Genotype	No. of pts	%	No. of pts	%	No. of pts	%	No. of pts	%
KIT 11 (n = 176)	15	8.5	97	55.1	61	34.7	3	1.7
KIT 9 (n = 30)	0	0	11	36.7	18	60.0	1	3.3
WT (n = 23)	0	0	16	69.6	4	17.4	3	13.0
KIT 13 (n = 2)	0	0	0	0	2	100.0	0	0
KIT 17 (n = 2)	0	0	2	100.0	0	0	0	0
PDFGRA 18 (n = 2)	0	0	0	0	1	50.0	1	50.0
Total (n = 235)	15	6.4	126	54.6	86	36.6	8	3.4

CR, complete response; KIT 9, mutation of KIT exon 9; KIT 11, mutation of KIT exon 11; KIT 13, mutation of KIT exon 13; KIT 17, mutation of KIT exon 17; PD, progressive disease; PDGFRA 18, mutation of PDGFRA 18; PR, partial response; SD, stable disease; WT, wild type (no mutation of KIT or PDGFRA).

Figure 1. Progression-free survival for all patients (A) and by tumor genotype (B). N, number of patients.

Figure 2. Overall survival for all patients (A) and by tumor genotype (B). N, number of patients; NR, not reached.

Table III. Multivariate analyses of the prognostic factors of progression-free and overall survival (n = 290).

		Progression-free survival			Overall survival
Factor		HR	95% CI	p-value	HR	95% CI	p-value
ECOG PS	0–1	1		0.005	1		0.151
	2–3	2.385	1.309–4.348		2.305	0.737–7.208
Neutrophil (/μl)	≤7500	1		0.003	1		0.034
	>7500	3.756	1.569–8.993		5.534	1.136–26.947
Tumor genotype	KIT 11	1			1
	KIT 9	2.427	1.348–4.367	0.003	2.104	0.602–7.359	0.244
	WT	2.187	1.145–4.176	0.018	3.819	1.367–10.665	0.011
	Others*	7.680	3.005–19.623	<0.001	22.930	4.600–114.298	<0.001

CI, confidence interval; ECOG PS, Eastern Cooperative Oncology Group performance status; HR, hazard ratio; KIT 9, mutation of KIT exon 9; KIT 11, mutation of KIT exon 11; WT, wild type (no mutation of KIT or PDGFRA).

*Others were KIT exon 13 mutants (n = 2), KIT exon 17 mutants (n = 2), PDGFRA exon 12 mutant (n = 1), and PDGFRA exon 18 mutants (n = 3).