Table 6.

Relationship between colon radiation dose and risk of second primary solid cancer among survivors of various types of cancer within the LSS cohort

Stomach cancer survivors
Colon dose, Gy	Number of 2nd primary cases	RR*	95% CI
<0.005	101	1.00	ref
0.005–0.49	93	0.78	0.58–1.04
0.50–0.99	8	0.80	0.39–1.65
1.00–1.99	8	1.28	0.62–2.64
≥2.00	6	2.34	1.02–5.39†
ERR/Gy*		0.39	−0.01–0.96
Colon cancer survivors
Colon dose, Gy	Number of 2nd primary cases	RR*	95% CI
<0.005	39	1.00	ref
0.005–0.49	51	1.23	0.79–1.91
0.50–0.99	5	1.31	0.51–3.38
1.00–1.99	4	1.52	0.53–4.30
≥2.00	1	1.16	0.16–8.55
ERR/Gy*		0.27	NE‡-1.27
Thyroid cancer survivors
Colon dose, Gy	Number of 2nd primary cases	RR*	95% CI
<0.005	15	1.00	ref
0.005–0.49	19	0.80	0.40–1.59
0.50–0.99	9	2.05	0.87–4.87
1.00–1.99	7	3.36	1.32–8.57†
≥2.00	5	2.79	0.99–7.85
ERR/Gy*		1.24	0.27–3.10†
Lung cancer survivors
Colon dose, Gy	Number of 2nd primary cases	RR*	95% CI
<0.005	15	1.00	Ref
0.005–0.49	24	1.38	0.69–2.75
0.50–0.99	1	0.33	0.04–2.62
1.00–1.99	3	1.95	0.55–6.96
≥2.00	1	3.42	0.43–27.04
ERR/Gy*		0.12	NE‡-1.36
Female breast cancer survivors
Colon dose, Gy	Number of 2nd primary cases	RR*	95% CI
<0.005	35	1.00	Ref
0.005–0.49	59	1.30	0.85–1.99
0.50–0.99	9	1.12	0.54–2.34
1.00–1.99	10	2.45	1.21–4.95†
≥2.00	11	4.17	2.08–8.35†
ERR/Gy*		1.05	0.42–2.01†
Thyroid cancer survivors
Colon dose, Gy	Number of 2nd primary cases	RR*	95% CI
<0.005	17	1.00	Ref
0.005–0.49	24	0.87	0.46–1.63
0.50–0.99	3	1.24	0.36–4.29
1.00–1.99	5	3.80	1.34–10.75†
≥2.00	3	3.40	0.97–11.93
ERR/Gy*		1.25	0.21–3.26†

^*Relative risk (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 (second primary cancer risk estimates only).

^†p<0.05

^‡The lower bound of the confidence interval could not be estimated (NE) by the statistical model.