TABLE 5.

Models for Excess Absolute Risk per 10,000 Person-Years (EAR) as a Function of Radiation Dose to the Thyroid Gland in the Childhood Cancer Survivor Study Cohort

Model number	Description	Equation	β1	β2	β3	Deviance	Referent model	P valuea
1	Baselineb	αc	_	_	_	1532.5
2	Linear	α + β1d	0.458	_	_	1478.1	1	<0.001
3	Quadratic	α + β1d 2	0.00805	_	_	1516.1	1	<0.001
4	Linear exponential	α + β1d × exp(β2d)	2.547	−0.0582	_	1439.8	2	<0.001
5	Linear exponential quadratic model-1	α + β1d × exp(β2d2)	1.830	−0.00151	_	1429.4	2	<0.001
6	Linear exponential quadratic model-2	α + β1d × exp(β2d + β3d2)	0.759	0.100	−0.00381	1425.0	5	0.04
7	Linear quadratic	α + β1d + β2d2	1.030	−0.0156	_	1448.9	2	<0.001
8	Linear quadratic exponential	α + (β1d + β2d2) × exp(β3d)	2.351	−0.0370	−0.0327	1436.5	7	<0.001
9	Linear quadratic exponential quadratic	α + (β1d + β2d2) × exp(β3d2)	0.284	0.169	−0.00270	1424.1	5	0.02
10	Quadratic exponential quadratic	α + β1d2 × exp(β2d2)	0.197	−0.00284		1424.3	3	<0.001

Note. Italics represent the most parsimonious models with the lowest deviance and compatibility with radiobiological theory.

^aLikelihood ratio test comparing to referent model.

^bBaseline function includes natural logarithm of attained age, sex and type of childhood cancer (Hodgkin lymphoma, leukemia or other).

^cα represents the baseline function as described in footnote b.