Additional Biomarkers beyond RAS That Impact the Efficacy of Cetuximab plus Chemotherapy in mCRC: A Retrospective Biomarker Analysis

Table 3

Efficacy outcomes according to RAS status and predictive model in validation cohort.

	RAS assessable; (n=141)		RAS wild-type; (n=123)		RAS wild-type/; Model-defined responsive group; (n=83)		RAS wild-type/; Model-defined refractory group; (n=40)
	Cetuximab plus chemotherapy; (n=67)	Chemotherapy alone; (n=74)	Cetuximab plus chemotherapy; (n=58)	Chemotherapy alone; (n=65)	Cetuximab plus chemotherapy; (n=42)	Chemotherapy alone; (n=41)	Cetuximab plus chemotherapy; (n=16)	Chemotherapy alone; (n=24)
Overall response
CR	1 (1.5%)	1 (1.4%)	1 (1.7%)	1 (1.5%)	1 (2.4%)	1 (2.4%)	0 (0%)	0 (0%)
PR	39 (58.2%)	21 (28.4%)	37 (63.8%)	18 (27.7%)	33 (78.6%)	11 (26.8%)	4 (25.0%)	7 (29.2%)
SD	16 (23.9%)	26 (35.1%)	12 (20.7%)	23 (35.4%)	6 (14.2%)	14 (34.1%)	6 (37.5%)	9 (37.5%)
PD	10 (14.9%)	25 (33.8%)	7 (12.1%)	22 (33.8%)	2 (4.8%)	14 (34.1%)	5 (31.3%)	8 (33.3%)
Not assessable	1 (1.5%)	1 (1.4%)	1 (1.7%)	1 (1.5%)	1 (2.4%)	1 (2.2%)	0 (0%)	0 (0%)
ORR, %	59.7	29.7	65.5	29.2	81.0	29.3	25.0	29.2
OR	3.50		4.60		7.45		0.59
95% CI	1.74-7.04		2.15-9.84		2.88-19.27		0.05-5.61
P (Chi-square or Fisher's)	<0.001		<0.001		<0.001		1.000
p for interaction test					0.005
Radical resection rate of LM, %	28.4	10.8	32.8	10.8	40.5	9.8	12.5	12.5
OR	3.27		4.04		6.29		1.00
95% CI	1.32-8.08		1.55-10.51		1.89-20.92		0.15-6.77
p(Chi-square or Fisher's)	0.008		0.003		0.001		1.000
PFS, months
Median	10.0	5.8	10.5	5.6	11.3	4.7	8.6	7.4
95%CI	7.5-10.5	3.7-6.3	8.2-11.8	3.7-6.3	9.0-13.0	2.1-5.9	6.7-9.3	4.6-7.5
HR	0.63		0.54		0.45		0.83
95%CI	0.44-0.91		0.37-0.80		0.28-0.74		0.44-1.59
p(log-rank)	0.004		<0.001		0.001		0.534
p for interaction test					0.094
OS, months
Median	31.7	23.7	36.8	21.6	42.0	20.3	24.8	23.0
95%CI	21.2-44.8	15.7-28.3	23.4-48.6	15.6-28.4	NE-NE	11.4-28.6	20.6-27.4	14.3-29.7
HR	0.54		0.45		0.27		0.92
95%CI	0.33-0.89		0.26-0.77		0.13-0.58		0.41-2.06
p(log-rank)	0.011		0.003		<0.001		0.828
p for interaction test					0.020

1 early death (less than 3 months) and 1 lost to follow-up before the first time evaluation by MDT.
CR, complete response; PR, partial response; SD, stable disease; PD, progressive disease; ORR, objective response rate; LM, liver metastases; PFS, progression free survival; OS, overall survival; HR, hazard ratio; OR, odds ratio; 95% CI, 95% confidence interval. MDT, multidisciplinary team; NE, not evaluable.