Table 2.
Odds ratios and 95% confidence intervals for completion of 5 years or more of tamoxifen for chemoprevention according to Sister Study participant characteristics
| Participant characteristics | Tamoxifen ≥5 y | Tamoxifen <5 y | OR (95% CI)* | OR (95% CI)† |
|---|---|---|---|---|
| No. (%) | No. (%) | |||
| Total | 237 (100.0) | 318 (100.0) | N/A | N/A |
| Age at tamoxifen initiation, y | ||||
| 26–44 | 50 (21.1) | 72 (22.6) | 0.84 (0.51 to 1.37) | 0.75 (0.44 to 1.28) |
| 45–49 | 62 (26.2) | 74 (23.3) | 1.01 (0.63 to 1.63) | 0.98 (0.59 to 1.60) |
| 50–54 | 63 (26.6) | 76 (23.9) | 1.0 (reference) | 1.0 (reference) |
| 55–59 | 34 (14.3) | 47 (14.8) | 0.87 (0.50 to 1.52) | 0.93 (0.52 to 1.66) |
| 60–73 | 28 (11.8) | 49 (15.4) | 0.69 (0.39 to 1.22) | 0.79 (0.43 to 1.46) |
| Race | ||||
| Non-Hispanic white | 222 (93.7) | 279 (87.7) | 1.0 (reference) | 1.0 (reference) |
| Black | 9 (3.8) | 20 (6.3) | 0.57 (0.25 to 1.27) | 0.61 (0.27 to 1.40) |
| Hispanic | 3 (1.3) | 10 (3.1) | 0.38 (0.10 to 1.39) | 0.33 (0.09 to 1.24) |
| Smoking status at tamoxifen initiation | ||||
| Never | 121 (51.1) | 151 (47.5) | 1.0 (reference) | 1.0 (reference) |
| Former | 94 (39.7) | 129 (40.6) | 0.91 (0.64 to 1.30) | 0.90 (0.62 to 1.30) |
| Current | 21 (8.9) | 37 (11.6) | 0.71 (0.39 to 1.27) | 0.75 (0.41 to 1.39) |
| Menopausal status at tamoxifen initiation | ||||
| Premenopausal | 109 (46.0) | 125 (39.3) | 1.0 (reference) | 1.0 (reference) |
| Postmenopausal | 76 (32.1) | 118 (37.1) | 0.74 (0.50 to 1.09) | 0.77 (0.48 to 1.23) |
| BCRAT score at enrollment‡ | ||||
| <1.67 | 1 (0.4) | 15 (4.7) | 0.10 (0.01 to 0.81) | 0.08 (0.01 to 0.67) |
| 1.67–2.99 | 35 (14.8) | 53 (16.7) | 1.0 (reference) | 1.0 (reference) |
| 3.00–5.99 | 115 (48.5) | 156 (49.1) | 1.13 (0.69 to 1.83) | 1.19 (0.72 to 1.95) |
| ≥6.00 | 85 (35.9) | 92 (28.9) | 1.41 (0.85 to 2.36) | 1.60 (0.94 to 2.72) |
| Mean score (SD), continuous trend | 5.4 (2.3) | 5.1 (2.7) | 1.04 (0.97 to 1.11) | 1.07 (1.00 to 1.15) |
| Raloxifene | ||||
| Never | 197 (83.1) | 236 (74.2) | 1.0 (reference) | 1.0 (reference) |
| Yes, prior to tamoxifen start age | 14 (5.9) | 15 (4.7) | 1.12 (0.53 to 2.37) | 1.19 (0.55 to 2.60) |
| Yes, after tamoxifen start age | 26 (11.0) | 67 (21.1) | 0.47 (0.29 to 0.76) | 0.45 (0.27 to 0.75) |
| Sister(s) diagnosed with breast cancer before starting tamoxifen | ||||
| No | 87 (36.7) | 90 (28.3) | 1.0 (reference) | 1.0 (reference) |
| Yes, one sister | 117 (49.4) | 179 (56.3) | 0.67 (0.46 to 0.98) | 0.71 (0.48 to 1.04) |
| Yes, more than one sister | 33 (13.9) | 49 (15.4) | 0.70 (0.41 to 1.18) | 0.76 (0.44 to 1.32) |
| BRCA1/2 testing | ||||
| No | 208 (87.8) | 262 (82.4) | 1.0 (reference) | 1.0 (reference) |
| Yes | 27 (11.4) | 55 (17.3) | 0.62 (0.38 to 1.02) | 0.61 (0.36 to 1.02) |
| BRCA1/2 mutation carrier§ | ||||
| No | 25 (10.5) | 31 (9.7) | 1.0 (reference) | 1.0 (reference) |
| Yes | 2 (0.8) | 19 (6.0) | 0.13 (0.03 to 0.62) | N/A |
* Odds ratio and 95% confidence interval among 555 women who reported formerly using tamoxifen (n = 515) or currently using tamoxifen and starting five or more years before study enrollment (n = 40). BCRAT = Breast Cancer Risk Assessment Tool; CI = confidence interval; N/A = not applicable; OR = odds ratio.
† Mutually adjusted for other variables in the table except BCRAT score (a composite variable) or BRCA1/2 mutation testing or carrier status (because of small sample sizes).
‡ Adjusted for smoking status, menopausal status, and raloxifene use.
§ Among women who reported undergoing BRCA1/2 testing.