Table 1. Characteristics of full cohort, breast cancer recurrence cases and matched controls.
| Characteristic | Full cohort (n=1376) | Casesa (n=94) | Controlsa,b (n=458) |
|---|---|---|---|
|
Patient details | |||
|
Age—mean (s.d.) | |||
| Years |
65.0 (10.2) |
64.3 (10.0) |
64.3 (10.1) |
|
Comorbidity—mean (s.d.) | |||
| Drug classes |
8.4 (6.3) |
9.0 (7.1) |
8.1 (6.1)c |
|
Smoking status (%) | |||
| Current | 319 (23.2) | 23 (24.5) | 98 (21.6) |
| Never | 706 (51.3) | 40 (42.6) | 241 (52.6)c |
| Past | 160 (11.6) | 15 (16.0) | 53 (11.4)c |
| Unspecified |
191 (13.9) |
16 (17.0) |
66 (14.4) |
|
Deprivation index (%) | |||
| 1—least deprived | 183 (13.3) | 14 (14.9) | 57 (12.1) |
| 2 | 139 (10.1) | 11 (11.7) | 49 (10.5) |
| 3 | 168 (12.2) | 10 (10.6) | 62 (13.2) |
| 4 | 238 (17.3) | 19 (20.2) | 74 (15.8) |
| 5—most deprived | 542 (39.4) | 30 (31.9) | 183 (41.3)c |
| Not assigned |
106 (7.7) |
10 (10.6) |
33 (7.0)c |
|
Tumour details | |||
|
Tumour stage (%)d | |||
| I | 446 (32.4) | 13 (13.8) | 65 (13.8) |
| IIa / IIb | 447/316 (32.5/23.0) | 28/29 (29.8/30.9) | 140/145 (29.8/30.9) |
| IIIa / IIIb-c |
79/88 (5.7/6.4) |
11/13 (11.7/13.8) |
48 / 60 (11.7/13.8) |
|
Tumour grade (%) | |||
| Low | 173 (12.6) | 6 (6.4) | 42 (9.0) |
| Intermediate | 743 (54.0) | 41 (43.6) | 246 (53.2)c |
| High | 342 (24.9) | 38 (40.4) | 125 (28.2)c |
| Unspecified |
118 (8.6) |
9 (9.6) |
45 (9.6) |
|
PR (%) | |||
| Negative | 197 (14.3) | 20 (21.3) | 68 (14.8) |
| Positive | 919 (66.8) | 54 (57.4) | 300 (65.6)c |
| Unspecified |
260 (18.9) |
20 (21.3) |
90 (19.7)c |
|
HER-2 (%) | |||
| Negative | 797 (57.9) | 50 (53.2) | 258 (56.7) |
| Positive | 128 (9.3) | 11 (11.7) | 43 (9.1) |
| Unspecified |
451 (32.8) |
33 (35.1) |
157 (34.2) |
|
Treatment details | |||
| Chemotherapy (%)e | 449 (32.6) | 39 (41.7) | 187 (41.5) |
| Radiation (%)f |
936 (68.0) |
60 (63.8) |
318 (69.6)c |
|
First hormonal therapy (%) | |||
| Tamoxifen | 685 (49.8) | 59 (62.8) | 261 (56.8) |
| Toremifene | 0 (0.0) | 0 (0.0) | 0 (0.0) |
| Anastrozole | 586 (42.6) | 29 (30.9) | 166 (36.6) |
| Letrozole | 99 (7.2) | 6 (6.4) | 28 (6.0) |
| Exemestane |
6 (0.4) |
0 (0.0) |
3 (0.6) |
|
Other drug exposures (%) | |||
| Aspirin | 357 (25.9) | 23 (24.5) | 117 (25.7) |
| Statin hydrophilic | 302 (21.9) | 18 (19.1) | 89 (19.2) |
| Statin lipophilic |
36 (2.6) |
1 (1.1) |
17 (3.6)c |
|
Recurrence details | |||
|
Follow-up—mean (s.d.) | |||
| Years | 2.70 (1.14) | 1.86 (1.01) | 1.86 (1.04) |
| Breast cancer recurrences (%) | 95 (6.9) | — | — |
| Woman-years |
3716 |
— |
— |
|
Breast cancer recurrence rate | |||
| Recurrence/1000 years |
25.6 |
— |
— |
|
Recurrence sites (%)g | |||
| Liver | 11 (11.6) | — | — |
| Lung | 8 (8.4) | — | — |
| Bone | 46 (48.4) | — | — |
| Brain | 7 (7.4) | — | — |
| Other sites | 20 (21.1) | — | — |
| Unspecified | 11 (11.6) | — | — |
Abbreviations: HER-2=human epidermal growth factor receptor 2; PR=progesterone receptor; s.d.=standard deviation.
Cases: women with a breast cancer recurrence within 4 years of hormonal therapy initiation. Controls: women without a breast cancer recurrence at the time of a matched case's recurrence. Controls were randomly matched to cases in a ratio of 5 : 1, on tumour stage at diagnosis and age within a calliper of 5 years, using incidence density sampling without replacement.
Means and percentages for controls are weighted by the inverse number of controls matched to each case; 89 cases had 5 matched controls, 1 case had 4 matched controls, 2 cases had 3 matched controls, 1 case had 2 matched controls and 1 case had 1 matched control.
Weighted standardized difference (d) between cases and controls >0.1.
AJCC Cancer Staging Manual 6th Edition. Springer (Greene et al, 2002).
Chemotherapy received prior to hormonal therapy initiation.
Radiation received in the year post diagnosis.
Seven women had more than one simultaneous site of recurrence.