Table 3.

Relationship of Clomiphene and Gonadotropin Use to Breast Cancer Risk

	Breast cancers (n=749)	Person-Years	HR1	95% CI
Never Use of Clomiphene or Gonadotropins	450	173,457	1.00	referent
Clomiphene Use
Ever Use	284	107,036	1.05	0.90–1.22
Dosage (mg)
1–900	99	36,338	1.06	0.85–1.32
901–2250	77	34,323	0.88	0.69–1.12
≥2251	108	36,375	1.20	0.97–1.48
p for trend			0.39
Cycles
<6	175	69,954	0.97	0.81–1.15
6–11	73	25,670	1.15	0.89–1.48
≥12	36	11,412	1.37	0.97–1.92
p for trend			0.21
Age at first use
<30	116	49,620	1.07	0.87–1.32
30–34	90	36,504	0.92	0.73–1.16
≥35	62	13,927	1.31	1.00–1.73
Unknown	16	6,985	0.87	0.53–1.44
Gonadotropin Use
Ever Use	82	26,639	1.14	0.89–1.44
Dosage (ampules)2
1–25	30	8,927	1.26	0.87–1.83
26–64	25	8,907	1.03	0.69–1.54
≥65	27	8,805	1.12	0.76–1.66
p for trend			0.40
Cycles
<6	67	22,001	1.12	0.87–1.46
≥6	15	4,638	1.19	0.71–2.00
p for trend			0.33
Age at first use
<30	24	7,993	1.33	0.88–2.02
30–34	25	11,150	0.85	0.56–1.27
≥35	31	7,123	1.32	0.91–1.92
Unknown	2	373	1.83	0.45–7.36
Combination of Clomiphene and Gonadotropins
Clomiphene only	217	85,236	1.02	0.87–1.21
Gonadotropins only	15	4,839	1.12	0.67–1.88
Both	67	21,800	1.14	0.88–1.48

¹HRs adjusted for study site, calendar year of first infertility evaluation, gravidity at first clinic visit.

²One ampule = 75 IU of gonadotropins.