TABLE II.

Pituitary and thyroid dosimetry and corresponding risk of hypothyroidism, stratified by radiotherapy exposure and adjusted for diagnosis year and age, race/ethnicity, and sex.

Treatment group	Pituitary dose, Gy median (IQR)	Thyroid dose, Gy median (IQR)	Hypothyroid – all individuals			Hypothyroid – on supplementation
			n	HR	(95% CI)	n	HR	(95% CI)
Chemotherapy only	0 (-)	0 (-)	10	1	ref	4	1	ref
Cranial <20 Gy, no spinal radiotherapy	16.8 (8.8–17.0)	0.7 (0.5–0.8)	12	1.5	(0.7, 3.6)	2	0.6	(0.1, 3.2)
Cranial ≥20 Gy, no spinal radiotherapy	22.5 (21.6–24.0)	0.8 (0.6–1.1)	16	1.7	(0.7, 4.2)	10	2.1	(0.6, 7.9)
Cranial <20 Gy, any spinal radiotherapy	17.8 (12.5–18.2)	12.0 (10.1–14.4)	1	2.0	(0.2, 16.0)	1	4.5	(0.5, 43.3)
Cranial ≥20 Gy, any spinal radiotherapy	24.3 (23.9–27.0)	16.6 (11.0–19.8)	17	8.3	(3.3, 20.5)	9	11.1	(2.9, 41.7)
Siblings, males*			5	0.2	(0.04, 1.02)	2	0.2	(0.01, 2.5)
Siblings, females*			45	0.7	(0.3, 1.7)	23	1.2	(0.2, 6.3)

IQR, interquartile range; HR, hazard ratio;

^*adjusted only for race/ethnicity and compared with same-sex survivors who received chemotherapy only.