Reconceptualizing the clinicopathological features, locoregional therapy and prognostic factors of occult breast cancer in the era of molecular subtyping

Figures & data

Figure 1. Flowchart of patient selection and study development.

Table 1. Clinicopathological characteristics of OBC and non-OBC patients.

		Non-OBC (n = 113,612)	OBC (n = 691)	Statistical value	P
Age (years)	<40	8,815 (7.76 percent)	26 (3.76 percent)	z = −5.71	.001
	40–49	22,856 (20.12 percent)	93 (13.46 percent)
	50–59	29,744 (26.18 percent)	188 (27.21 percent)
	60–69	28,019 (24.66 percent)	210 (30.39 percent)
	70–79	16,184 (14.24 percent)	131 (18.96 percent)
	≥80	7,994 (7.04 percent)	43 (6.22 percent)
Race	Black	14,895 (13.11 percent)	83 (12.01 percent)	χ^2 = 2.45	.293
	White	86,779 (76.38 percent)	545 (78.87 percent)
	Other	11,938 (10.51 percent)	63 (9.12 percent)
Marital status	Married	63,003 (55.45 percent)	395 (57.16 percent)	χ^2 = 2.36	.307
	Unmarried	18,735 (16.49 percent)	99 (14.33 percent)
	Other	31,874 (28.06 percent)	197 (28.51 percent)
LN metastasis	N1	87,818 (77.30 percent)	429 (62.08 percent)	z = −10.08	.001
	N2	17,010 (14.97 percent)	141 (20.41 percent)
	N3	8,784 (7.73 percent)	121 (17.51 percent)
pTNM	I	9,401 (8.27 percent)	17 (2.46 percent)	z = −5.99	.001
	II	70,132 (61.73 percent)	412 (59.62 percent)
	III	34,079 (30.00 percent)	262 (37.92 percent)
Hormone receptor	Negative	19,962 (17.57 percent)	240 (34.73 percent)	χ^2 = 139.03	.001
	Positive	93,650 (82.43 percent)	451 (65.27 percent)
HER-2	Negative	92,108 (81.07 percent)	485 (70.19 percent)	χ^2 = 52.88	.001
	Positive	21,504 (18.93 percent)	206 (29.81 percent)
Subtype	Luminal B	14,973 (13.18 percent)	126 (18.23 percent)	χ^2 = 176.88	.001
	Luminal A	78,677 (69.25 percent)	325 (47.03 percent)
	HER2-enriched	6,531 (5.75 percent)	80 (11.58 percent)
	Triple-negative	13,431 (11.82 percent)	160 (23.15 percent)
Breast surgery	No surgery	5,422 (4.77 percent)	380 (54.99 percent)	χ^2 = 3.6e + 03	.001
	BCS	45,433 (39.99 percent)	78 (11.29 percent)
	Mastectomy	62,757 (55.24 percent)	233 (33.72 percent)
Axilla surgery	No surgery	6,863 (6.04 percent)	105 (15.20 percent)	χ^2 = 127.23	.001
	PLND	33,354 (29.36 percent)	122 (17.66 percent)
	ALND	73,395 (64.60 percent)	464 (67.15 percent)
Chemotherapy	No (Unknown)	35,318 (31.09 percent)	129 (18.67 percent)	χ^2 =  49.50	.001
	Yes	78,294 (68.91 percent)	562 (81.33 percent)
Radiotherapy	No (Unknown)	46,993 (41.36 percent)	292 (42.26 percent)	χ^2 =  0.23	.634
	Yes	66,619 (58.64 percent)	399 (57.74 percent)

OBC, occult breast cancer; LN, lymph node; pTNM, pathological TNM staging; BCS, breast-conserving surgery; PLND, positive lymph node dissection; ALND, axillary lymph node dissection.

Table 2. Multivariable analysis of OS and BCSS in OBC patients (n = 651).

Variable		HR for OS (95%CI)	P	HR for BCSS (95%CI)	P
Age (years)	≥ 60 vs. < 60	1.51 (0.99–2.30)	.058	1.24 (0.75–2.04)	.405
Race	Black	Reference		Reference
	White	0.76 (0.44–1.33)	.338	0.76 (0.38–1.55)	.458
	Others	0.63 (0.26–1.57)	.323	0.49 (0.15–1.62)	.243
Marital status	Married	Reference		Reference
	Unmarried	1.99 (1.11–3.58)	.022	1.18 (0.53–2.65)	.683
	Other	1.61 (1.05–2.49)	.031	1.59 (0.95–2.67)	.078
pTNM stage	III vs. II + I	1.91 (1.26–2.89)	.002	2.57 (1.54–4.29)	.001
Subtype	Luminal B	Reference		Reference
	Luminal A	1.66 (0.83–3.32)	.151	1.46 (0.59–3.61)	.411
	HER2-enriched	2.40 (1.07–5.39)	.034	3.22 (1.20–8.63)	.020
	Triple-negative	2.96 (1.45–6.04)	.003	3.87 (1.57–9.54)	.003
Locoregional therapy	Observation	Reference		Reference
	BCT + ALD without RT	0.25 (0.14–0.44)	.001	0.23 (0.11–0.48)	.001
	BCT + ALD with RT	0.17 (0.10–0.30)	.001	0.22 (0.11–0.44)	.001
	Mastectomy + ALD without RT	0.10 (0.04–0.22)	.001	0.08 (0.03–0.25)	.001
	Mastectomy + ALD with RT	0.17 (0.09–0.34)	.001	0.15 (0.06–0.36)	.001
Chemotherapy	Yes vs. No	0.84 (0.51–1.37)	.485	0.97 (0.50–1.88)	.920

OBC, occult breast cancer; HR, hazards ratio; CI, confidence interval; LN, lymph node; pTNM, pathological TNM staging; BCT, breast-conserving treatment; ALD, axillary lymphadenectomy; RT, radiotherapy.

Data availability statement

The data that support the findings of this study are available from the corresponding author, [XC], upon reasonable request.