Table 1

Hypothetical combinations of relative risks r_K-ras , r_wild and overall relative risk for cancer given the that the odds ratio r_K-ras/r_wild among cases is 3.7 and P_K-ras/P_wild = 1.25

r_K-ras	r_wild	Overall relative risk
1.0	0.27	0.68
1.25	0.34	0.84
1.50	0.41	1.01
1.75	0.47	1.18
2.0	0.54	1.35

The estimates of the odds ratio (3.7) and P_K-ras/P_wild (1.25) are as found by Porta and colleagues.2