Table 5.

Association Between Duration of Cigarette Smoking, Amount of Cigarette Smoking, and Years Since Quit Before and After Diagnosis and Death As a Result of Breast Cancer and All Causes

Cigarette Smoking Variable Before and After Diagnosis	No. (%) of Patients (N = 4,562)	Cause of Death
		Breast Cancer		All Causes
		No. of Deaths (n = 246)	HR* (95% CI)	No. of Deaths (n = 988)	HR* (95% CI)
Duration of smoking, years†
Never/never	2,219 (49)	116	1 (Reference)	421	1 (Reference)
Former/former
< 30	1,135 (25)	54	0.92 (0.65 to 1.30)	192	1.27 (1.06 to 1.52)
≥ 30	422 (9)	21	1.18 (0.72 to 1.93)	150	1.77 (1.45 to 2.16)
Recent/former
< 30	94 (2)	9	1.59 (0.77 to 3.27)	19	2.32 (1.42 to 3.79)
≥ 30	258 (6)	11	0.93 (0.49 to 1.78)	84	2.33 (1.81 to 2.99)
Recent/current
< 30	111 (2)	11	1.94 (0.98 to 3.85)	17	1.92 (1.14 to 3.23)
≥ 30	323 (7)	24	1.63 (1.01 to 2.64)	105	2.69 (2.13 to 3.41)
Amount of smoking, pack-years†
Never/never	2,219 (49)	116	1 (Reference)	421	1 (Reference)
Former/former
< 30	1,205 (26)	54	0.89 (0.63 to 1.25)	232	1.30 (1.10 to 1.54)
≥ 30	352 (8)	21	1.38 (0.84 to 2.26)	110	1.96 (1.56 to 2.45)
Recent/former
< 30	168 (4)	10	1.00 (0.51 to 1.97)	39	1.84 (1.30 to 2.61)
≥ 30	184 (4)	10	1.36 (0.69 to 2.67)	64	2.81 (2.12 to 3.73)
Recent/current
< 30	183 (4)	12	1.39 (0.74 to 2.62)	36	1.86 (1.30 to 2.66)
≥ 30	251 (6)	23	1.94 (1.19 to 3.17)	86	3.09 (2.39 to 4.00)

Abbreviation: HR, hazard ratio.

^*HR stratified by age at diagnosis, study phase, state of residence, and stage at diagnosis and adjusted for education, body mass index, parous status, age at first birth, menopausal status, use of postmenopausal hormone therapy, mammography history, alcohol consumption, first-degree family history of breast cancer, postdiagnosis body mass index, postdiagnosis alcohol consumption, and time from diagnosis to postdiagnosis questionnaire.

^†Duration and pack-years calculated for smoking before diagnosis.