Table 4.

Univariable and multivariable Cox regression analysis with local recurrence as the primary endpoint

	Univariable analysis		Multivariable analysis
	HR (95% CI)	p value	HR (95% CI)a	p value
DIEP
Immediate	1.00 (reference)		1.00 (reference)
Delayed	0.804 (0.483–1.337)	0.400	2.890 (1.536–5.437)	0.001
Age at operation
≤ 40	1.00 (reference)	< 0.001	1.00 (reference)	< 0.001
41–50	0.274 (0.142–0.527)	< 0.001	0.044 (0.016–0.121)	< 0.001
≥ 51	0.330 (0.187–0.582)		0.102 (0.045–0.232)	< 0.001
Histological tumor type
In situ	1.00 (reference)b		1.00 (reference)b
Invasive
T stage
0	1.00 (reference)b		1.00 (reference)b
In situ
1
2
3
4
N stage
0	1.00 (reference)b		1.00 (reference)b
1
2
3
y stage
Yes	1.00 (reference)		1.00 (reference)
No	2.640 (1.141–6.110)	0.023	1.405 (0.496–3.980)	0.522
Bloom Richardson grade
1	1.00 (reference)b		1.00 (reference)
2			0.677 (0.349–1.314)	0.249
3			0.148 (0.049–0.448)	0.001
Axillary treatment
No treatment	1.00 (reference)b		1.00 (reference)b
SLN
ALND
SLN + ALND
Chemotherapy
Yes	1.00 (reference)		1.00 (reference)
No	2.976 (1.801–4.918)	< 0.001	7.404 (3.146–17.425)	< 0.001
Radiation therapy
Yes	1.00 (reference)		1.00 (reference)
No	0.583 (0.365–0.932)	0.024	0.347 (0.180–0.669)	0.002
Endocrine therapy
Yes	1.00 (reference)		1.00 (reference)
No	1.098 (0.672–1.793)	0.710	1.835 (0.955–3.526)	0.068
Immunotherapy
Yes	1.00 (reference)		1.00 reference
No	1.628 (0.703–3.769)	0.256	1.036 (0.370–2.900)	0.947

y neoadjuvant therapy before mastectomy; SLN sentinel lymph node; ALND axillary lymph node dissection

^aAdjusted for immortal time bias, age at operation, histological tumor type, TN stage, y stage, Bloom Richardson grade, axillary treatment, chemotherapy, radiation therapy, endocrine therapy and immunotherapy

^bToo few events to validly estimate associations