. 2017 Mar 8;102(7):2575–2583. doi: 10.1210/jc.2016-3529

Table 2.

Evaluation of Effect Modification for the Thyroid Cancer Radiation Dose Response, Including Numbers of Radiation-Exposed Cases and Fitted RR at 0.2 Gy Under an Additive Adjustment for Treatment With Chemotherapy

Modifier	Data With Doses <0.2 Gy			Data With Doses <0.1 Gy
Modifier	Cases	RR_{0.2 Gy}^a	θ	Cases	RR_0.2Gy^a	θ
None	252	3.2	2.84	184	2.9	2.17
Sex
Male	58	4.2	2.93	44	5.0	2.31
Female	194	3.0		140	2.4
P value^b		0.35			0.15
Age at exposure (y)
<1	40	1.6	3.49	30	0.4	2.77
1–4	64	4.2		31	2.9
5–9	84	3.9		71	3.9
10–14	42	3.5		35	3.7
15–19	22	1.6		17	0.6
P value^c		0.01			0.05
Attained age (y)
<20	17	9.4	3.72	10	7.5	2.49
20–29	43	5.5		25	4.1
30–39	48	2.6		33	2.0
40–49	60	2.2		48	2.6
50–59	62	3.1		52	3.2
60⁺	22	2.5		16	1.9
P value^c		0.01			0.13
Time since exposure (y)
<20	37	5.3	3.16	22	4.2	2.41
20–29	49	3.5		36	3.5
30–34	33	3.4		22	1.7
35–39	33	3.3		22	2.3
40–44	36	2.4		28	2.2
45⁺	64	2.3		54	3.2
P value^c		0.02			0.26
Number of treatments^d
1	226	3.5	2.80	170	3.4	2.13
≥2	20	2.4		8	0.4
P value^b		0.25			0.25

Pooled data limited to doses <0.2 Gy or <0.1 Gy.

Fitted RRs from a linear model in radiation dose with an additive effect for chemotherapy treatment, c, $RR (d, x_{t}) = 1 + β d + θ c$ . Models adjusted for study, sex, age, and study-specific factors (see text). For modifiers, $({\sum^{}}_{j} β_{j} z_{j}$ d) replaced βd where z_j was an indicator variable for category j and β_j was a linear parameter. There were 142 with nonexposed cases. For <0.2 Gy and <0.1 Gy, β estimates with 95% CI were 11.1 (6.6, 19.7) and 9.6 (3.7, 17.0), respectively.

^{^a}

Fitted RR at 0.2 Gy.

^{^b}

P value for likelihood ratio test of no variation based on a binary modifier.

^{^c}

P value for likelihood ratio test of no variation based on continuous modifier.

^{^d}

The definition of fractionation, which involved time between fractions, dose per fraction, and reason, varied by study. One treatment included all dose fractions received within 6 months in most studies and within 1 year for the Tinea Capitis Study.