TABLE 1

Risk of concordant histology-specific lung cancer

Histologic type	Negative family history	One lung cancer case in the family		At least two lung cancer cases in the family		Trend test p-value
Histologic type	Negative family history	Cases	RR (95% CI)	Cases	RR (95% CI)	Trend test p-value
Overall	21 602	2598	2.11^# (2.00–2.23)	177	3.75^# (3.07–4.57)	<0.0001^¶
Adenocarcinoma	9342	334	2.37^# (2.08–2.69)	11	5.83^# (2.93–11.61)	<0.0001^¶
SCC	3894	147	2.40^# (1.95–2.94)	5	7.81^# (2.63–23.23)	<0.0001^¶
Small cell	2513	25	2.56^# (1.56–4.21)	0		0.0013^¶
Large cell	2981	31	2.80^# (1.91–4.09)	0		<0.0001^¶

RR: relative risk; SCC: squamous cell carcinoma. ^#: significantly increased RR at the two-sided 5% level, 1% level and 0.1% level; ^¶: statistically significant.