Table 3.
GEP Testing and Chemotherapy Use Stratified by Clinical Risk Category
| Variable | Clinical Risk Based on Clinical Characteristics (and guideline-recommended therapy)* |
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low (recommend no chemotherapy)† |
Intermediate (consider testing and chemotherapy)‡ |
High (recommend chemotherapy)§ |
||||||||||
| No. | % | OR | 95% CI | No. | % | OR | 95% CI | No. | % | OR | 95% CI | |
| No. of patients | 1,111 | 3,254 | 2,941 | |||||||||
| Proportion who had GEP testing | 13.8 | 11.8 to 15.9 | 36.8 | 35.2 to 38.5 | 5.1 | 4.3 to 6.0 | ||||||
| Proportion who received chemotherapy | ||||||||||||
| All patients | 4.9 | 3.7 to 6.3 | 37.1 | 35.4 to 38.8 | 82.3 | 80.9 to 83.6 | ||||||
| Stratified by test use¶ | ||||||||||||
| If tested | 17.0 | 11.4 to 23.9 | 33.5 | 30.9 to 36.3 | 45.3 | 37.2 to 53.7 | ||||||
| If not tested | 2.9 | 2.0 to 4.2 | 39.1 | 37.0 to 41.3 | 84.3 | 82.9 to 85.6 | ||||||
| Odds of receiving chemotherapy:tested versus not tested | ||||||||||||
| Unadjusted | 6.80 | 3.9 to 12.0 | 0.78 | 0.68 to 0.91 | 0.15 | 0.11 to 0.22 | ||||||
| Adjusted∥ | 11.13 | 5.39 to 22.99 | 0.59 | 0.49 to 0.71 | 0.11 | 0.07 to 0.17 | ||||||
NOTE. Sixty-nine patients (0.9% of the total cohort) could not be classified into a clinical risk group because of missing clinical characteristics (eg, grade or human epidermal growth factor receptor 2 [HER2] status).
Abbreviation: GEP, gene expression profile.
Consensus and evidence-based recommendations made by the National Comprehensive Cancer Network breast cancer clinical practice guidelines are based on stage and other clinical characteristics.
No chemotherapy recommended for invasive ductal/lobular cancers if stage T1aN0 or stage T1bN0 without unfavorable features (high nuclear or histologic grade, angiolymphatic invasion, or HER2 overexpression) or for tubular/colloid cancers in which the tumor is < 3 cm and nodes are not involved.
Consider testing and chemotherapy for invasive ductal/lobular cancers if stage T1bN0 with unfavorable features or if the tumor is > 1 cm, nodes are not involved, and HER2 is not overexpressed.
Recommend chemotherapy for tubular/lobular cancers in which the tumor is ≥ 3 cm and for invasive ductal/lobular cancers in which the tumor is > 1 cm, nodes are not involved, and HER2 is positive, or any node-positive cancers.
P values for χ2 test analyzing chemotherapy use among patients who did v did not have GEP testing were < .001 for the no chemotherapy, consider testing and chemotherapy, and recommend chemotherapy groups.
Multivariable logistic regression model predicting odds of receiving chemotherapy within each stratum, controlling for test use, age, race, education, insurance, employment status, comorbidity, year of diagnosis, type of cancer center, grade, HER2 status, tumor size, and number of involved nodes (recommend chemotherapy group only). Factors consistently associated with lesser odds of receiving chemotherapy across all three strata included age ≥ 50 v< 50 years; education to high school or less v beyond high school; having Medicare v indemnity insurance; having ≥ two comorbid conditions v ≤ one; having a ≤ 1-cm v > 1-cm tumor; and having a low- v high-grade cancer. Of note, there was no significant interaction between GEP testing and year of diagnosis in the model predicting chemotherapy use.