TABLE 5.

Parameter Estimates for the Best Fitting Model^a for the Excess Relative Risk (ERR) for All Thyroid Cancers, Papillary Tumors, and Non-Papillary Tumors

Case groupb	β	γ1	γ2	γ3	θ	P valuec	P valued	RR0.2 Gye (95% CI)	RR10 Gye (95% CI)
All thyroid cancers	5.45	0.016	−0.001	−0.281	2.58	<0.001	0.001	2.7 (2.2–3.5)	30.4 (20.9–44.4)
Papillary tumors	3.68	0.055	−0.002	−0.377	1.97	<0.001	0.009	2.4 (1.9–3.1)	22.4 (14.4–35.3)
Non-papillary tumors	10.78	−0.009	−0.0009	−0.220	2.72	<0.001	0.234	4.1 (2.4–7.7)	55.7 (21.2–148.5)

^aModel for the ERR with continuous radiation dose: ERR(d) = βd exp{γ₁d + γ₂d² + γ₃ln(d)}, with linear parameter β and the γ’s parameters defining the curvature. Models fitted with an additive adjustment for treatment with chemotherapy, x_t, RR(d, x_t) = 1 + ERR(d) + θx_t. Models also adjusted for study, sex, age and other study-specific factors (see text).

^bAmong the 1,070 thyroid cancer cases, 841 were papillary tumors, 143 cases were classified as non-papillary tumors (with 95 follicular, 8 medullary, 5 anaplastic, 17 other and 18 unspecified) and 86 cases had no information on histology.

^cP value for test of no departure from linearity, γ₁ = γ₂ = γ₃ = 0.

^dP value for test of no effect of chemotherapy (θ = 0).

^eFitted RR at 0.2 and 10 Gy, approximately the trials-weighted mean doses in exposed subjects in non-CCSS (0.22 Gy) and CCSS (9.3 Gy) studies.