Table 5.

Rate of subsequent breast cancer among survivors diagnosed between 1996 and 2006 with ER+ or PR+ receptor status and followed through 2008 by adjuvant hormonal treatment groups among women with invasive disease and not exposed to chemotherapy

Type	N	Person-years of exposure	Number of subsequent BCa	Rate per 1000 P-Y (95% CI)	Crude HR	95% CI	Adjusted HR1	95% CI
Women with MPR3 ≥80%	8720	43,507	979	22.50 (21.11–23.96)
Tamoxifen only	2964	21,196	314	14.81 (13.22–16.55)	0.37	0.32–0.43	0.40	0.34–0.46
AI only	1611	5083	118	23.22 (19.22–27.80)	0.51	0.41–0.62	0.35	0.28–0.43
Switchers2	1294	4308	60	13.93 (10.63–17.93)	0.50	0.38–0.67	0.37	0.27–0.50
No hormones	2851	12,921	487	37.69 (34.42–41.19)	1.00	Reference	1.00	Reference
Women with MPR3 ≥80%	5869	30,586	492	16.09 (14.70–17.57)
Tamoxifen only	2964	21,196	314	14.81 (13.22–16.55)	1.00	Reference	1.00	Reference
AI only	1611	5083	118	23.22 (19.22–27.80)	1.47	1.18–1.83	0.96	0.72–1.29
Switchers2	1294	4308	60	13.93 (10.63–17.93)	1.06	0.79–1.41	0.87	0.64–1.19

¹Adjusted for age at diagnosis, year of diagnosis, race/ethnicity, household income, health-care visits, hospitalizations, comorbidity, stage at diagnosis, primary treatment, histology, grade, tumor size, lymph nodes, ER, PR, and HER2/neu status, menopause.

²Switched from tamoxifen to aromatase inhibitor.

³MPR, medication possession ratio.