Impact of Oncotype DX risk categorization and receipt of chemotherapy on survival outcomes among patients with small...

The application of genomic assays, such as Oncotype DX, in patients with small (T1mi/a/b) clinically node-negative (N0-N1mi) hormone receptor positive breast cancer (HR+BC) is becoming increasingly popular in real-world clinical practice. Whether these results can be reliably prognostic among this clinically low-risk population and can be used to make decisions on the application of adjuvant chemotherapy remains unknown.

Data from the National Cancer Database (NCDB) were examined for those diagnosed with small, node-negative HR+BC between 2010 and 2020. Oncotype DX recurrence score (RS) data were classified as low (RS < 11), intermediate (RS = 11-25), or high risk (RS = 26-100). Our primary objective was comparing overall survival (OS) based on chemotherapy receipt for those with high-risk scores. Kaplan-Meier methods and multivariable Cox proportional hazard models were used. Propensity score matching was additionally performed.

Of the 350 911 patients with T1mi/a/b N0/N0(i+)/N1mi HR+BC, 102 357 (29.2%) underwent Oncotype DX testing and had available RS data. Among them, 32 158 (31.4%) had low, 58 891 (57.5%) had intermediate, and 11 308 (11.0%) had high-risk. Chemotherapy receipt was documented in 1.2% (n = 402) of low-risk, 6.8% (n = 4000) of intermediate-risk, and 66.3% (n = 7496) of high-risk patients. Among high-risk patients, those who received chemotherapy had a lower risk of death compared with those in the chemotherapy omission arm, both on univariate (HR, 0.55; 95% CI, 0.52-0.72; P < 0.001) and multivariable (HR, 0.61; 95% CI, 0.52-0.72; P < 0.001) analyses. This finding remained true following propensity score matching (univariate HR, 0.63; 95% CI, 0.52-0.76; aHR, 0.71; 95% CI, 0.59-0.86; P < 0.001 for both). Factors associated with a high RS included higher tumor grade, Black race, and lymphovascular invasion.

Our findings suggest that risk stratification through a genomic assay such as Oncotype DX may be advantageous, even among otherwise clinically low-risk individuals with HR + BC.