Table 2.

Overall distribution of covariates and striated by breast cancer specific mortality and other cause mortality. Multivariable adjusted relationship between time-varying surveillance mammography and death

	Total		Breast cancer specific mortality			Other cause mortality
	N (%)	Follow-up Person-years (per 1,000)	Cases	IR	HRa (95% CI)	Cases	IR	HRa (95% CI)
Overall	1,235	9,015	120	13.3		393	43.6
Time-varying surveillance mammography		5,140	54	10.5	0.82 (0.56, 1.19)	185	36.0	0.95 (0.78, 1.17)
Age at year 6
70-74	456 (37)	3,804	41	10.8	Reference	92	24.2	Reference
75-79	383 (31)	3,017	34	11.3	1.12 (0.71, 1.77)	97	32.2	1.34 (1.01, 1.79)
80+	396 (32)	2,194	45	20.5	2.09 (1.34, 3.26)	204	93.1	3.44 (2.66, 4.44)
Time-varying Charlson Comorbidity Index
0		3,882	37	9.5	Reference	72	18.6	Reference
1		3,486	50	14.3	1.44 (0.94, 2.22)	172	49.3	2.35 (1.78, 3.10)
>1		1,647	33	20.0	1.94 (1.19, 3.15)	149	90.5	4.27 (3.19, 5.70)
Tumor stage at diagnosis
I	747 (60)	5,574	50	9.0	Reference	250	44.9	Reference
IIA	369 (30)	2,613	43	16.5	2.13 (1.45, 3.14)	115	44.0	1.11 (0.89, 1.38)
IIB	119 (9.6)	827	27	32.6		28	33.8
Primary surgery
BCS	603 (49)	4,430	49	11.1	0.96 (0.65, 1.41)	194	43.8	0.99 (0.80, 1.22)
Mastectomy	632 (51)	4,585	71	15.5	Reference	199	43.4	Reference
Year of diagnosis
1990	218 (18)	1,559	17	10.9		81	52.0
1991	213 (17)	1,547	24	15.5		67	43.3
1992	263 (21)	1,967	22	11.2		89	45.2
1993	285 (23)	2,067	27	13.1		87	42.1
1994	256 (21)	1,874	30	16.0		69	36.8
Race/ethnicity
White non-Hispanic	1007 (82)	7,214	101	14.0		317	44.0
Asian	32 (2.6)	306	1	3.3		9	29.4
African-American	125 (10)	943	12	12.7		44	46.7
Hispanic	70 (5.7)	552	6	10.9		23	41.7
Other/unknown	1 (0.1)	0	0	-		0	-
Charlson Comorbidity 5 year post-index
0	660 (53)	5,336	60	11.2		149	27.9
1	445 (36)	3,015	45	14.9		178	59.1
>1	130 (11)	664	15	22.6		66	99.4
ER/PR status
ER or PR +	936 (76)	6,877	96	14.3		299	43.5
ER/PR-	153 (12)	1,123	16	14.0		44	39.2
unknown	146 (12)	1,015	8	7.9		50	49.3
Radiation therapy complete
Yes	515 (42)	4,004	37	9.2		139	34.7
No	720 (58)	5,011	83	16.6		254	50.7
Adjuvant therapy
Tamoxifen, chemotherapy or both	859 (70)	6,353	102	16.1		263	41.4
Neither	376 (30)	2,662	18	6.8		130	48.9
Months since last surveillance mammogram at 5 years post-diagnosis
Median (Min, Max)	9.7 (0.01-60.9)		10.0 (0.01- 60.9)			10.5 (0.04-60.9)
Surveillance mammogram in year 4-5 following diagnosis
Yes	828 (67)	6,402	77	12.0		239	37.3
No	407 (33)	2,613	43	16.5		154	59.0
Number of surveillance mammograms in years 6+ following diagnosis
0	272 (22)	1,095	38	34.7		138	126.0
1	171 (14)	822	29	35.3		83	101.0
2	161 (13)	992	22	22.2		70	70.6
3	109 (8.8)	892	12	13.5		29	32.5
4	105 (8.5)	893	8	9.0		27	30.2
5	79 (6.4)	736	3	4.1		20	27.2
6	78 (6.3)	795	3	3.8		10	12.6
7	88 (7.1)	917	4	4.4		9	9.8
8	74 (6.0)	799	1	1.3		6	7.5
9	73 (5.9)	800	0	-		1	1.3
10	25 (2.0)	299	0	-		0	-
Median (Min, Max)	3 (0-10)		1 (0-8)			1 (0-9)

^aStratified by follow-up cycle and adjusted for: site, age at year 6, stage (I/IIA or IIB), primary surgery type, time-dependent Charlson comorbidity