Is age just a number? Oncotype DX testing and chemotherapy use in the post-TAILORx era

Trial Assigning Individualized Options for Treatment (TAILORx) redefined the Oncotype DX (ODX) risk stratification scores. This study describes the clinical application of ODX in the post-TAILORx era in relation to chemotherapy.

A cohort of 8017 early-stage breast cancer patients considered guideline-eligible for ODX testing were identified between 2015 and 2021. Clinical factors associated with ODX testing and adjuvant chemotherapy were found through descriptive analysis and multivariable logistic regression modeling. Models were adjusted for age, race/ethnicity, tumor size and grade, progesterone (PR) status, and Charlson Comorbidity Index. The Cochran-Armitage test was used to evaluate the probability of ODX testing during the study period.

ODX testing increased over time (from 45% in 2015 to 80% in 2021; p < .0001). The likelihood of chemotherapy use increased by an estimated 5% annually (adjusted odds ratio [aOR], 1.05; 95% CI, 1.01-1.09). Testing was more likely in younger than older patients (e.g., aOR 1.90 among 18 to <40 vs. 0.30 among 70 to <80 as compared to 60 to <70). The association of ODX testing with chemotherapy was modified by age. Although younger patients were more likely to receive chemotherapy, testing was associated with less chemotherapy use in younger patients and more chemotherapy in older patients (p value for interaction <.001).

In the post-TAILORx era, younger age was associated with substantially more ODX testing. The association of testing with chemotherapy varied substantially by age. The impact of age on ODX testing and use of chemotherapy is substantial and warrants further study.