Table 1.

Correlation between Ki67 labeling indexes/tumor grade and 21-gene recurrence score as categorical variables in women age < 50.

Variable	RS category based on TAILORx				Total	χ2	P value
	0–15	16–19	20–25	>25
Ki67 hotspot
<10	1	1	3	0	5 (3.3%)	30.08	0.0003
<20	23	14	0	0	37 (24.2%)
<30	20	8	4	2	34 (22.2%)
<40	20	9	7	4	40 (26.1%)
≥40	12	9	6	10	37 (24.2%)
Ki67 average
<10	37	19	6	3	65 (42.5%)	47.96	<0.0001
<20	32	17	11	5	65 (42.5%)
<30	5	5	1	1	12 (7.8%)
<40	2	0	2	4	8 (5.2%)
≥40	0	0	0	3	3(1.9%)
Ki67 hottest spot
<10	0	1	2	0	3 (1.9%)	27.76	0.0059
<20	14	10	1	0	25 (16.3%)
<30	22	11	2	1	36 (23.5%)
<40	19	7	6	4	36 (23.5%)
≥40	21	12	9	11	53 (34.6%)
Grade
1	24	9	2	1	36 (23.5%)	25.58	0.0003
2	46	29	13	7	95 (62.1%)
3	6	3	5	8	22 (14.4%)
Grade and Ki67 combined
Low risk (Grade 1 or Hotspot < 20)	36	18	5	1	60 (39.2%)	11.49	0.0094
High risk (others)	40	23	15	15	93 (60.8%)
Total	76 (49.6%)	41 (26.8%)	20 (13.9%)	16 (10.5%)	153