Table 2

Distribution of clinical and tumour characteristics by ER status and receipt of tamoxifen among the 5959 participants in a population-based cohort of premenopausal women diagnosed with first primary breast cancer, ProBe CaRe study

Patient and tumour characteristics	ER+/TAM+		ER−/TAM−
Patient and tumour characteristics	N	%	N	%
Total	4600	100	1359	100
Age at diagnosis
<35	222	4.8	182	23
35–39	487	11	229	27
40–44	1123	24	321	24
45–49	1668	36	385	28
50+	1100	24	242	18
Menopausal status at diagnosis
Premenopausal	4600	100	1359	100
Stage at diagnosis
Stage I	1184	26	402	29.6
Stage II	2476	54	702	51.7
Stage III	917	20	246	18.1
Unknown stage	23	0.5	9	0.7
Tumour size
<2 mm	2646	58	677	50
2≤5 mm	1780	39	632	47
>5 mm	156	3.4	44	3.2
Unknown	18	0.4	6	0.4
No of metastatic lymph nodes
0	1704	37	695	51
1	1148	25	238	17
2	583	13	116	9
3+	1152	25	306	23
Unknown	13	0.3	4	0.3
Lymph node evaluation
No	8	0.2	3	0.2
Yes	4592	100	1356	100
Histological grade
Unsuitable	10	0.2	13	1
I	955	21	21	1.5
II	2391	52	216	16
III	950	21	884	65
Unknown	294	6.4	225	17
Type of primary surgery
Mastectomy	2033	44	627	46
Lumpectomy	2567	56	732	54
Progesterone receptor status
PR−	383	8.3	1121	83
PR+	2680	58	19	1.4
Unknown/not measured	1537	33	219	16
HER2 status
HER2−	2887.00	63	692	51
HER2+	619	14	354	26
Unknown/not measured	1094	24	313	23
Intention to treat with chemotherapy
No	144	3	14	1
Yes	4456	97	1345	99
Chemotherapy
No	437	9	109	8
Yes	4163	91	1250	92
Intention to treat with tamoxifen
No	70	1.5	1351	99
Yes	4530	98	8	0.6
Radiation therapy
No	655	14	267	20
Yes	3945	86	1092	80
Anti-HER2 therapy
No	2887	63	692	51
Yes	619	13	354	26
Unknown	1094	24	313	23
Recurrence
No	4204	91	1143	84
Yes	396	8.6	216	16
Another malignancy
No	4544	99	1341	99
Yes	56	1.2	18	1.3
Dead at end of follow-up
No	4239	92	1115	82
Yes	361	8	244	18
Charlson Comorbidity Score
0	4587	99	1344	99
1	4	0.1	4	0.3
2	2	0	3	0.2
3+	7	0.2	8	0.6

ER, oestrogen receptor; HER, human epidermal growth factor receptor 2; ProBe CaRe, Predictors of Breast Cancer Recurrence; PR, progesterone receptor; TAM, tamoxifen therapy.