Table 4.

Relationship between radiation dose and risk of second primary solid tumors by time since the first primary cancer diagnosis

Colon dose, Gy	Number of 2nd primary cases	RR*	95% CI
Second primary diagnosed 180 days to 5 years after the first primary cancer
<0.005	194	1.00	ref
0.005–0.49	238	1.08	0.89–1.31
0.50–0.99	28	1.12	0.75–1.67
1.00–1.99	30	1.88	1.28–2.76†
≥2.00	10	1.44	0.76–2.73
ERR per gray		0.37	0.10–0.71†
Second primary diagnosed 5 to 10 years after the first primary cancer
<0.005	62	1.00	ref
0.005–0.49	104	1.40	1.02–1.93†
0.50–0.99	11	1.18	0.62–2.25
1.00–1.99	17	3.19	1.85–5.49†
≥2.00	13	5.25	2.86–9.65†
ERR per gray		1.25	0.64–2.09†
Second primary diagnosed >10 years after the first primary cancer
<0.005	145	1.00	ref
0.005–0.49	133	0.73	0.57–0.92
0.50–0.99	16	0.76	0.45–1.29
1.00–1.99	15	1.48	0.84–2.53
≥2.00	15	2.59	1.49–4.41†
ERR per gray		0.45	0.13–0.87†

^*Relative risks (RR) and excess RR per Gray (ERR/Gy) are adjusted for sex, city, attained age, age at time of bombing, and age at first cancer diagnosis.

^†p<0.05.