Table 2.
Predictors of Gene Expression Profile Testing, Multivariable Logistic Regression Analysis
| Variable | OR | 95% CI | P |
|---|---|---|---|
| Age at diagnosis, years | < .001 | ||
| < 50 | 0.88 | 0.75 to 1.03 | |
| 50-59 | Ref | ||
| 60-69 | 0.79 | 0.65 to 0.95 | |
| 70+ | 0.26 | 0.19 to 0.35 | |
| Race/ethnicity | .018 | ||
| White non-Hispanic | Ref | ||
| African American non-Hispanic | 0.70 | 0.54 to 0.92 | |
| Other/unknown* | 0.86 | 0.70 to 1.06 | |
| Education | .014 | ||
| Above high school | Ref | ||
| High school degree or less | 0.63 | 0.52 to 0.76 | |
| Other/unknown† | 1.06 | 0.90 to 1.24 | |
| Health insurance | < .001 | ||
| Managed care | 0.64 | 0.51 to 0.81 | |
| Indemnity | Ref | ||
| Medicare | 0.66 | 0.49 to 0.89 | |
| Other/unknown‡ | 0.59 | 0.43 to 0.80 | |
| Year of diagnosis | < .001 | ||
| 2006 | Ref | ||
| 2007 | 1.59 | 1.34 to 1.88 | |
| 2008 | 2.68 | 2.27 to 3.18 | |
| Type of cancer center | < .001 | ||
| Comprehensive | Ref | ||
| Community-based | 0.59 | 0.48 to 0.72 | |
| Size of primary tumor, cm§ | < .001 | ||
| ≤ 1 | 0.32 | 0.28 to 0.38 | |
| 1.1-2 | Ref | ||
| ≥ 2.1 | 0.43 | 0.36 to 0.51 | |
| Unknown | 0.14 | 0.04 to 0.47 | |
| No. of nodes involved | < .001 | ||
| 0 | Ref | ||
| 1-3 | 0.11 | 0.09 to 0.14 | |
| 4+ | 0.03 | 0.02 to 0.06 | |
| Unknown | 0.19 | 0.08 to 0.43 | |
| Hormone receptor status | < .001 | ||
| ER positive/PR positive | Ref | ||
| ER positive/PR negative | 0.80 | 0.66 to 0.97 | |
| ER negative/PR positive | 0.25 | 0.12 to 0.54 | |
| ER positive or PR positive/the other unknown | 0.55 | 0.10 to 2.96 | |
| HER2 status | < .001 | ||
| Not overexpressed | Ref | ||
| Overexpressed | 0.20 | 0.16 to 0.27 | |
| Unknown | 0.24 | 0.10 to 0.56 | |
| Histologic or nuclear grade | .043 | ||
| Low | Ref | ||
| Intermediate or high | 1.15 | 0.98 to 1.34 | |
| Unknown/missing | 0.70 | 0.43 to 1.14 | |
| Lymphovascular invasion | .019 | ||
| Absent | Ref | ||
| Present | 0.81 | 0.66 to 0.95 | |
| Unknown/missing | 1.46 | 0.95 to 2.26 | |
| Histologic type | .010 | ||
| Ductal and/or lobular | Ref | ||
| Other ¶ | 0.66 | 0.48 to 0.90 |
NOTE. A sensitivity analysis excluding all patients with any missing values yielded similar results, except that race/ethnicity, type of cancer center, histologic/nuclear grade, and lymphovascular invasion were no longer significant predictors.
Abbreviations: ER, estrogen receptor; HER2, human epidermal growth factor receptor 2; OR, odds ratio; PR, progesterone receptor; Ref, reference group.
Other race/ethnicity includes Hispanic, African American Hispanic, Asian, American Indian-Aleut, Eskimo, and unclassified. There were 69 patients with unknown race/ethnicity.
Other/unknown includes 41 patients with unclassified education status and 2,366 with unknown values.
Other/unknown includes 556 patients with unclassified health insurance status and 130 with unknown values.
Size categories based on pathologic data, unless pathologic data were unavailable or patients received neoadjuvant chemotherapy, in which case clinical data were used.
Other histology includes tubular, colloid, medullary, adenocystic, and papillary.