Table 3.
Breast Cancer Risk Assessment Tool’s discrimination (c-statistics and 95% confidence intervals) among Nurses’ Health Study (n = 71 293) and the Women’s Health Initiative Extension study (n = 79 611) participants
| Discrimination | NHS* | WHI-ES* | ||||||
|---|---|---|---|---|---|---|---|---|
| Overall (n = 71 293) |
57–74 y† (n = 52 111) |
75+ y (n = 19 182) |
P‡ age comparison | Overall (n = 79 611) |
55–74 y (n = 57 009) |
75+ y (n = 22 602) |
P‡ age comparison |
|
| Primary analyses‡,§ | ||||||||
| BCRAT c-statistic (95% CI) | 0.565 (0.549 to 0.580) |
0.564 (0.546 to 0.582) |
0.569 (0.538 to 0.600) |
.78 | 0.578 (0.563 to 0.592) |
0.577 (0.560 to 0.594) |
0.579 (0.552 to 0.606) |
.91 |
| Sensitivity analyses | ||||||||
| Limited to women who underwent mammography in past 2 y (NHS = 52 380, WHI = 67 457) | 0.567 (0.549 to 0.585) |
0.567 (0.547 to 0.588) |
0.564 (0.529 to 0.599) |
.86 | 0.582 (0.567 to 0.597) |
0.581 (0.563 to 0.599) |
0.585 (0.556 to 0.614) |
.82 |
| Limited to women without significant illness|| (NHS = 55 567, WHI = 63 437) | 0.563 (0.545 to 0.581) |
0.563 (0.543 to 0.584) |
0.563 (0.527 to 0.599) |
1.00 | 0.571 (0.555 to 0.587) |
0.573 (0.554 to 0.592) |
0.563 (0.532 to 0.595) |
.60 |
| Limiting outcome to estrogen receptor–positive breast cancers (NHS = 70 295, WHI = 79 343) | 0.568 (0.550 to 0.587) |
0.562 (0.541 to 0.583) |
0.598 (0.562 to 0.635) |
.09 | 0.578 (0.563 to 0.594) |
0.576 (0.557 to 0.594) |
0.586 2
(0.556 to 0.616) |
.56 |
| Sensitivity analyses (changing SEER incidence)§ | ||||||||
| Using SEER incidence rates from 2006–2010 (NHS = 71 293, WHI = 79 611) |
0.567 (0.551 to 0.583) |
0.566 (0.548 to 0.585) |
0.569 (0.538 to 0.599) |
.90 | 0.575 (0.561 to 0.590) |
0.575 (0.559 to 0.592) |
0.576 (0.549 to 0.603) |
.99 |
* Nurses’ Health Study included participants alive in 2004. Women’s Health Initiative Extension Study began in 2005. CI = confidence interval; NHS = Nurses’ Health Study; SEER = Surveillance, Epidemiology, and End Results; WHI-ES = Women’s Health Initiative Extension Study.
† The youngest women in NHS in 2004 were age 57 years.
‡ To assess discrimination in each cohort, we calculated the c-statistic or area under the receiver operating characteristic (ROC) curve and its standard error (21). To test if c-statistics differed by age within cohort, we used the normal approximation z-test.
§ For our primary analyses, we used SEER breast cancer incidence rates from 1983–1987 for whites, from 1994–1998 for blacks, from 1990–1996 for Hispanics, and from 1988–2002 for Asians. In sensitivity analyses, we used SEER incidence rates from 2006–2010 for whites, blacks, and Hispanics.
|| Significant illnesses included: history of diabetes, myocardial infarction, congestive heart failure, stroke, emphysema, and peripheral artery disease.