252P - Adjuvant chemotherapy in T1a/bN0 breast cancer patients with high oncotype DX recurrence scores (RS>25)

Background

RS>25 is prognostic for distant recurrence and predictive for adjuvant chemotherapy (aChem) benefit in ER+HER2-negative early breast cancer (BC), independent of tumor size. For patients with tumors >0.5 cm and candidates for aChem, current NCCN guidelines recommend strongly considering OncotypeDX testing and aChem treatment for RS>25. Herein, we sought to evaluate the benefit of aChem in T1a/bN0 early BC patients with high RS>25 tested. We used the Clalit Health Services (CHS) dataset, the largest HMO in Israel, with more than 4.5 million insurers.

Methods

We identified all CHS patients tested between Feb-2006 and Dec-2019 with T1a/bN0 early breast cancer and a RS>25. Demographic, clinicopathological, and treatment data were extracted from the CHS centralized registry. A propensity score matching method based on nearest neighbor with replacements was used to balance differences. Kaplan-Meier analysis with log-rank test was used to test differences in clinicopathological characteristics. Freedom from recurrence of BC locally and at a distant site and freedom from second primary cancer and death also known as invasive disease-free survival (iDFS) between the treatment groups.

Results

159 patients were identified of which 76 patients (47.7%) received aChem. Before applying the propensity- score matching aChem was more common among younger patients >50-years-old (25%) compared with patients ≤70-years-old (7.9)%, healthier patients with Charlson comorbidity score 0-1 (70%) compared with 30.2% for score ≥2, among Oncotype RS >30 72.5%. aChem was more often omitted in invasive lobular carcinoma (75%) and grade 1 tumors (72.7%). Propensity score matching balanced discrepancies among both treatment groups and Kaplan-Meier analysis demonstrated no iDFS improvement with aChem in T1a/bN0 early BC patients with high Oncotype DX recurrence scores (RS>25).

Conclusions

Utility of aChem in T1a-bN0 tumors and RS>25 is dependent on clinocopathologic variables beyond RS. After balancing between these variables no iDFS benefit for aChem was observed.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.