Survival after breast cancer in women with type 2 diabetes using antidiabetic medication and statins: a retrospective cohort study

Figures & data

Figure 1. Flowchart showing how the cohort was formed.

Table 1. Distribution of baseline characteristics and outcome status in the different medication groups.

		Antidiabetic medication (ADM)					Use of statins
		Metformin^a (%)	Other oral ADM^a (%)	Metformin and other oral ADM^a (%)	Insulin (%)	No history of regular ADM^b (%)	Yes^a (%)	No^b (%)	Total (%)
Total	n	658	444	752	686	993	1,402	2,131	3,533
Age at diagnosis	Median	68	77	73	74	70	71	74	72
	IQR^c	62─77	68─83	64─80	66─80	62─79	64─78	64─81	64─80
Diagnosis age categories
	40─59	113 (17)	43 (10)	106 (14)	74 (11)	187 (19)	166 (12)	357 (17)	523 (15)
	60─69	251 (38)	95 (21)	189 (25)	185 (27)	319 (32)	499 (36)	540 (25)	1,039 (29)
	70─79	209 (32)	141 (32)	254 (34)	249 (36)	275 (28)	486 (35)	642 (30)	1,128 (32)
	80─100	85 (13)	165 (37)	203 (27)	178 (26)	212 (21)	251 (18)	592 (28)	843 (24)
Diabetes duration in years
	Median	3.4	4.9	7.3	11.9	6.5	7.1	6.1	6.5
	IQR^c	2.0─5.6	2.7─7.7	4.4─11.2	7.9─16.0	2.0─10.9	3.5─12.0	2.9─10.6	3.1─11.2
Diabetes duration categories
	0.5─<3	296 (45)	128 (29)	96 (13)	30 (4)	300 (30)	300 (21)	550 (26)	850 (24)
	3─<6	211 (32)	159 (36)	199 (26)	60 (9)	169 (17)	296 (21)	502 (24)	798 (23)
	6─<12	118 (18)	113 (25)	302 (40)	254 (37)	327 (33)	456 (33)	658 (31)	1,114 (32)
	12─<42	33 (5)	44 (10)	155 (21)	342 (50)	197 (20)	350 (25)	421 (20)	771 (22)
Stage
	Local	331 (50)	233 (52)	348 (46)	291 (42)	541 (54)	695 (50)	1,049 (49)	1,744 (49)
	Advanced	291 (44)	174 (39)	355 (47)	322 (47)	387 (39)	615 (44)	914 (43)	1,529 (43)
	Unknown	36 (5)	37 (8)	49 (7)	73 (11)	65 (7)	92 (7)	168 (8)	260 (7)
Outcome at the end of follow-up
	Breast cancer death	88 (13)	91 (21)	119 (16)	142 (21)	160 (16)	186 (13)	414 (19)	600 (17)
	Other death	75 (11)	174 (39)	221 (29)	242 (35)	221 (22)	248 (18)	685 (32)	933 (26)
	Alive	495 (75)	179 (40)	412 (55)	302 (44)	612 (62)	968 (69)	1,032 (48)	2,000 (57)

^aDuration of medication use ≥180 days.

^bDuration of medication use <180 days three years before breast cancer diagnosis.

^cInterquartile range.

Figure 2. Cumulative mortality curves for the two causes of death in the different medication groups. ADM: antidiabetic medication; M&O: metformin and other oral ADM.

Table 2. Estimation results from Cox proportional hazard models of mortality from breast cancer, other causes of death, and all causes.

Variable	Value	Mortality from breast cancer	Mortality from other causes	Mortality from all causes
		Hazard ratio (95% CI)	Hazard ratio (95% CI)	Hazard ratio (95% CI)
Year of diagnosis
	1998–2002	1	1	1
	2003–2007	0.90 (0.74–1.11)	0.93 (0.80–1.09)	0.92 (0.82–1.05)
	2008–2011	0.99 (0.78–1.24)	0.85 (0.68–1.05)	0.92 (0.79–1.07)
Age at diagnosis (years)
	40–59	0.94 (0.70–1.27)	0.57 (0.40–0.82)	0.77 (0.61–0.96)
	60–69	1	1	1
	70–79	1.62 (1.30–2.01)	3.03 (2.45–3.74)	2.31 (1.99–2.69)
	80–100	2.56 (2.02–3.25)	8.17 (6.60–10.12)	5.12 (4.38–5.98)
Duration of diabetes (years)
	0.5–<3	1	1	1
	3–<6	0.94 (0.74–1.20)	0.99 (0.80–1.23)	0.96 (0.82–1.13)
	6–<12	1.01 (0.80–1.28)	1.20 (0.98–1.46)	1.12 (0.96–1.3)
	12–<42	1.03 (0.79–1.35)	1.21 (0.96–1.51)	1.13 (0.95–1.34)
Stage
	Local	1	1	1
	Advanced	5.26 (4.28–6.46)	1.10 (0.95–1.26)	1.94 (1.74–2.16)
	Unknown	2.35 (1.62–3.41)	1.49 (1.20–1.85)	1.68 (1.4–2.02)
Prediagnostic statin use
	No	1	1	1
	Yes	0.76 (0.63–0.92)	0.75 (0.64–0.87)	0.75 (0.67–0.85)
Prediagnostic ADM group
	Metformin	0.86 (0.63–1.17)	0.73 (0.55–0.97)	0.79 (0.65–0.97)
	Other^a	1	1	1
	Metformin and other^a	0.80 (0.60–1.06)	1.01 (0.82–1.24)	0.92 (0.78–1.09)
	Insulin	1.16 (0.86–1.55)	1.45 (1.16–1.80)	1.32 (1.11–1.57)
	No history of regular ADM use	0.93 (0.71–1.21)	0.81 (0.66–0.99)	0.86 (0.73–1.01)

^aOther oral antidiabetic medication.

ADM: antidiabetic medication; 95% CI: 95% confidence interval.

Availability of data and material

The data that support the findings of this study are available from the National Institute for Health and Welfare, but restrictions apply to the availability of these data and so they are not publicly available. Data are, however, available upon reasonable request and with the permission of the National Institute for Health and Welfare, the Social Insurance Institution and Statistics Finland.