Table 1.

Clinicopathological characteristics of study population according to stage at initial diagnosis.

Characteristic	Stage at initial diagnosis				All (n=926)		p-value
	Stage 0-III (n=714)		Stage IV (de novo MBC) (n=212)
	N	%	N	%	N	%
Age at initial diagnosis, median (range)	47.6a (17.7–82.7)		50.6 (18.4–83.8)		48.1 (17.7–83.8)		9.55e–05
Race
Caucasian	627	87.8	188	88.7	815	88.0	0.066
African American	26	3.6	12	5.7	38	4.1
Asian or Pacific Islander	21	2.9	8	3.8	29	3.1
Other	22	3.1	0	0.0	22	2.4
Unknown	18	2.5	4	1.9	22	2.4
Sex
Female	710	99.4	209	98.6	919	99.2	0.418
Male	4	0.6	3	1.4	7	0.8
Ethnicity
Spanish/Hispanic	28	3.9	7	3.3	35	3.8	0.264
Non-Spanish; non-Hispanic	630	88.2	195	92.0	825	89.1
Unknown	56	7.8	10	4.7	66	7.1
Histologic Subtype
DCIS	14	2.0	0	0	14	1.5	0.006
Invasive Ductal (IDC)	533	74.6	146	68.9	679	73.3
Invasive Lobular (ILC)	71	9.9	35	16.5	106	11.4
Mixed (IDC and ILC)	54	7.6	26	12.3	80	8.6
Tubular	2	0.3	0	0	2	0.2
Mucinous	4	0.6	1	0.5	5	0.5
Other	9	1.3	1	0.5	10	1.1
Unknown	27	3.8	3	1.4	30	3.2
Histologic Grade
Well differentiated	41	5.7	11	5.2	52	5.6	0.175
Moderately differentiated	255	35.7	88	41.5	343	37.0
Poorly differentiated	365	51.1	105	49.5	470	50.8
Unknown	53	7.4	8	3.8	61	6.6
Subtype according to HR/HER2 status at initial diagnosis (primary)
HER2+/HR+	72	10.1	35	16.5	107	11.6	2.65e–08
HER2+/HR−	36	5.0	16	7.5	52	5.6
HER2−/HR+	379	53.1	136	64.2	515	55.6
TNBC	154	21.6	25	11.8	179	19.3
Unknown	73	10.2	0	0	73	7.9
Subtype according to HR/HER2 status at metastatic diagnosisb
HER2+/HR+	39	5.5	35	16.5	74	8.0	<2.2e–16
HER2+/HR−	41	5.7	16	7.5	57	6.2
HER2−/HR+	340	47.6	136	64.2	476	51.4
TNBC	142	19.9	25	11.8	167	18.0
Unknown	152	21.3	0	0	152	16.4
Stage at initial diagnosis
DCISc	14	2.0	0	0	14	1.5	-
Stage I	128	17.9	0	0	128	13.8
Stage II	329	46.1	0	0	329	35.5
Stage III	237	33.2	0	0	237	25.6
Stage IV	0	0	212	100.0	212	22.9
Unspecifiedd	6	0.8	0	0	6	0.6
Disease-free interval (until diagnosis of metastatic recurrence)
De novo MBC (stage IV at diagnosis)	0	0	212	100.0	212	22.9	-
≤2 years	191	26.8	0	0	191	20.6
>2 years	523	73.2	0	0	523	56.5
Type of sample tested
Primary	418	58.5	168	79.2	586	63.3	4.13e–07
Metastatic Recurrence	273	38.2	44	20.8	317	34.2
Local Recurrence	11	1.5	0	0	11	1.2
Unspecified	12	1.7	0	0	12	1.3
OncoPanel Version
1.0	150	21.0	40	18.9	190	20.5	0.561
2.0	564	79.0	172	81.1	736	79.5
Vital status
Alive	476	66.7	159	75.0	635	68.6	0.027
Dead	238	33.3	53	25.0	291	31.4

^a.Median age at initial diagnosis of breast cancer was 47.6 years in patients who later developed rMBC. In this group, the median age at diagnosis of metastatic recurrence was 53.6 years.

^b.In three patients who presented with initial diagnosis of HR+/HER2− dnMBC, OncoPanel was performed on a metastatic site of disease (collected > 180 days after initial diagnosis) that was TNBC (n=2) or HR+/HER2+ (n=1). In two patients with HR+/HER2+ dnMBC at initial diagnosis, OncoPanel was performed on a metastatic sample (collected >180 days after initial diagnosis) that was found to be HR−/HER2+.

^c.Patients with history of DCIS prior to the diagnosis of metastatic breast cancer (n=14) had a metastatic site of disease tested with OncoPanel.

^d.Cases are confirmed as early-stage invasive breast cancers, however, there was insufficient information available to classify by anatomic stage.