Breast conserving surgery versus mastectomy: overall and relative survival—a population based study by the Danish Breast Cancer Cooperative Group (DBCG)

Figures & data

Figure 1. Overall survival in the three groups: patients primarily assigned to mastectomy, patients primarily assigned to BCS, and patients primary assigned to BCS but who finally had mastectomy (BCS & Mast).

Table 1. Characteristics of 58,331 Danish breast cancer patients surgically treated in the period 1995–2002.

Characteristic	Mastectomy (final)		BCS (final)		BCS and mastectomy
	N	%	N	%	N	%	Total
	27,143	44.4	26,958	44.1	4230	6.9	58,331
Year of inclusion
1995–2001	12,735	47	4846	18	2249	53	19,830
2002–2007	9030	33	8907	33	1148	27	19,085
2007–2012	5378	20	13,205	49	833	20	19,416
Age at operation
18–44	2598	10	2631	10	672	16	5901
45–54	5227	20	6446	24	1239	29	12,912
55–64	6869	25	9497	35	1167	28	17,533
65–74	6656	25	6496	24	823	20	13,975
75+	5793	21	1888	7	329	8	8010
CCI
0	21,172	78	22,210	82	3572	84	46,954
1	3443	13	2907	11	375	9	6725
2	1565	6	1275	5	185	4	3025
3+	963	4	566	2	98	2	1627
Tumor size (mm)
0–10	2304	9	7063	26	1133	27	10,500
11–20	8842	33	13,893	52	1592	38	24,327
21–30	8371	31	4879	18	808	19	14,058
31–50	5471	20	949	4	443	11	6863
51+	1807	7	47	0	129	3	1983
Unknown	342	1	117	0	125	3	584
Positive lymph nodes
0	11,640	43	17,656	66	2409	57	31,705
1–3	8825	33	7333	27	1194	28	17,352
4–9	3936	15	1427	5	402	10	5765
10+	2742	10	542	2	225	5	3509
Histological type
Ductal	21,744	80	22,143	82	3204	76	47,091
Lobular	3487	13	2277	8	632	15	6396
Other	1699	6	2357	9	359	9	4415
Unknown	213	1	181	1	35	1	429
Grade (ductal and lobular)
I	6159	24	8776	36	990	256	15,925
II	10,624	42	9969	41	1532	40	22,125
III	6177	25	4861	20	761	20	11,799
Unknown	2271	9	814	3	553	14	3638
Estrogen receptor
Negative (0–9%)	6068	22	4023	15	905	21	10,996
Positive (10–100%)	19,999	74	22,412	83	3104	73	45,515
Unknown	1076	4	523	2	221	5	1820
HER2 receptor
Normal	7046	76	15,003	88	1063	78	23,112
Positive	2228	24	1999	12	302	22	4529
Unknown	17,869		9956		2865		30,690
Lymphovascular invasion
No	19,919	73	23,893	89	3162	75	46,974
Yes	5108	19	1952	7	488	12	7548
Unknown	2116	8	1113	4	580	14	3809
Multifocality
Multifocal	4302	16	741	3	832	20	5875
Unifocal	20,897	77	25,170	93	2878	68	48,945
Unknown	1944	7	1047	4	520	12	3511

BCS and mastectomy = patients initially assigned to BCS, but finally having mastectomy. Differences between groups were statistically significant for all variables with p values <.0001.

Table 2. Univariate and multivariate risk estimates for overall mortality and SMR.

	Unadjusted values				Adjusted values
	Overall mortality		SMR		Overall mortality		SMR
	RR	95% CI	RR	95% CI	RR	95% CI	RR	95% CI
M (ITT) versus BCS (ITT)	2.43	2.36–2.51	1.38	1.34–1.42	1.21	1.17–1.26	1.19	1.15–1.23
M (final) versus BCS (final)	2.46	2.38–2.54	1.44	1.39–1.48	1.23	1.18–1.28	1.20	1.15–1.25
BCS&M versus BCS (final)	1.51	1.43–1.60	1.28	1.21–1.36	1.10	1.03–1.17	1.08	1.01–1.15
M (ITT) versus BCS (final)	2.64	2.55–2.72	1.46	1.41–1.50	1.25	1.20–1.31	1.22	1.17–1.27

M = mastectomy; M (ITT) = patients primary allocated to mastectomy; M (final) = patents finally having mastectomy; BCS (ITT) = patients primary allocated to BCS; BCS (final) = patients finally having BCS; BCS&M  = patients initially allocated to BCS but finally having mastectomy.

Table 3. The impact on mortality of the patient, tumor, and treatment variables evaluated in a multivariate Poisson model on the intention to treat populations.

Variable	Overall mortality			SMR
	RR	95% CI	p value	RR	95% CI	p value
Operation			<.0001			<.0001
Mastectomy versus BCS	1.21	1.17–1.26		1.19	1.15–1.23
Age at operation			<.0001			<.0001
Age at operation 18–44 versus 55–64	0.71	0.67–0.76		4.13	3.88–4.40
Age at operation 45–54 versus 55–64	0.70	0.67–0.74		1.56	1.49–1.64
Age at operation 65–74 versus 55–64	1.56	1.50–1.62		0.62	0.60–0.65
Age at operation 75+ versus 55–64	2.45	2.34–2.57		0.34	0.33–0.36
Treatment program			<.0001			<.0001
Year of inclusion 2002–2007 versus 1995–2001	0.80	0.77–0.83		1.02	0.99–1.06
Year of inclusion 2008–2012 versus 1995–2001	0.56	0.53–0.59		0.90	0.86–0.95
CCI			<.0001			<.0001
CCI 1 versus 0	1.49	1.44–1.55		1.51	1.45–1.57
CCI 2 versus 0	1.66	1.58–1.75		1.72	1.63–1.81
CCI 3+ versus 0	2.33	2.18–2.48		2.53	2.37–2.69
Tumor size			<.0001			<.0001
Tumor size 0–10 versus 11–20^a mm	0.79	0.75–0.83		0.82	0.78–0.86
Tumor size 20–30 versus 11–20^a mm	1.19	1.15–1.23		1.19	1.15–1.23
Tumor size 30–50 versus 11–20^a mm	1.33	1.27–1.38		1.32	1.27–1.38
Tumor size 50+ versus 11–20^a mm	1.54	1.44–1.64		1.56	1.46–1.66
Positive lymph nodes			<.0001			<.0001
Positive lymph nodes 1–3 versus 0	1.38	1.33–1.43		1.35	1.30–1.40
Positive lymph nodes 4–9 versus 0	2.12	2.02–2.22		2.20	2.10–2.30
Positive lymph nodes 10+ versus 0	3.12	2.96–3.29		3.47	3.29–3.65
Estrogen receptor (ER) status			<.0001			<.0001
ER negative versus positive	1.20	1.14–1.25		1.19	1.14–1.25
ER unknown versus positive	1.06	0.99–1.13		1.07	1.00–1.15
Lymphovascular invasion			<.0001			<.0001
Lymphovascular invasion yes versus no^a	1.22	1.18–1.27		1.26	1.21–1.31
Histological type			.0001			<.0001
Lobular versus ductal	0.99	0.95–1.04		0.99	0.95–1.03
Other type^a versus ductal	0.89	0.84–0.94		0.87	0.83–0.92
Grade			<.0001			<.0001
Grade 2^a versus 1	1.14	1.10–1.19		1.14	1.10–1.18
Grade 3 versus 1	1.38	1.32–1.45		1.40	1.33–1.46
Focality			<.0001			.04
Multifocal versus unifocal	1.01	0.97–1.06		1.04	1.00–1.09
Unknown versus unifocal	1.17	1.11–1.22		1.05	1.00–1.11
RT			<.0001			<.0001
Unknown versus no	1.11	1.04–1.19		1.14	1.07–1.22
Yes versus no	0.83	0.80–0.87		0.93	0.89–0.97
Chemotherapy			<.0001			<.0001
Unknown versus no	1.65	1.53–1.78		1.94	1.79–2.09
Yes versus no	0.81	0.77–0.85		0.95	0.90–1.00
Endocrine therapy			<.0001			<.0001
Unknown versus no	1.70	1.58–1.83		1.78	1.65–1.91
Yes versus no	0.78	0.75–0.82		0.84	0.81–0.88

^a Unknown included in group.

Figure 2. Forrest plot showing interactions between selected risk factors and the risk of mortality (SMR) and the final surgical procedure.