SUMMARY: Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. It is estimated that in the US, approximately 316,950 new cases of female breast cancer will be diagnosed in 2025, and about 42,170 women will die of the disease, largely due to metastatic recurrence.
Approximately 50% of all breast cancers are Estrogen Receptor (ER) positive, HER2-negative, axillary node-negative tumors. In the treatment of early-stage breast cancer, particularly in Hormone Receptor-positive (HR-positive) and HER2-negative cases, the standard approach to adjuvant chemotherapy has evolved, with the goal of optimizing patient outcomes while minimizing unnecessary toxicity. Historically, anthracyclines, a class of chemotherapy drugs, were combined with taxanes as part of chemotherapy regimens. However, recent studies have questioned the benefit of adding anthracyclines to treatment, for patients with HR-positive/HER2-negative breast cancer, particularly in those with lower recurrence risk. The addition of anthracyclines has not definitively demonstrated improvements in outcomes like invasive Disease-Free Survival (DFS) for patients with HR-positive/HER2-negative breast cancer who receive taxane-based chemotherapy. Anthracycline-free regimens are typically preferred for lower risk patients, as efficacy is not compromised and there is no heightened risk of long-term side effects, such as leukemia. Yet, a gap exists in the literature regarding the benefit of anthracycline therapy in patients with high-risk profiles, as identified by OncotypeDX assay.
The Oncotype DX breast cancer assay, is a multigene genomic test that analyzes the activity of a group of 21 genes and is able to predict the risk of breast cancer recurrence and likelihood of benefit from systemic chemotherapy following surgery, in women with early-stage breast cancer. Oncotype Dx assay categorizes patients based on Recurrence Scores (RS) into Low risk (0-10), Intermediate risk (11-25), and High risk (26-100) helping clinicians tailor treatment decisions. Despite the widespread clinical use of OncotypeDX, the potential benefits of anthracyclines for patients with high RS scores have not been comprehensively studied.
The Anthracyclines in Early Breast Cancer (ABC) trials demonstrated that the addition of anthracyclines to a taxane-based chemotherapy regimen did not significantly improve invasive DFS for patients with HR-positive breast cancer. As a result, HR-positive/HER2-negative patients with a lower RS or smaller tumors have generally been managed with anthracycline-free regimens.
TAILORx ((Trial Assigning Individualized Options for Treatment) is a Phase III, randomized, prospective, non-inferiority trial in which 10,273 women, 18-75 years of age, with HR-positive, HER2-negative, T1b-T2N0 early-stage axillary node-negative breast cancer were enrolled. Patients had tumors 1.1-5.0 cm in size (or 0.6-1.0 cm and intermediate/high grade). Patients were divided into three groups based on their Recurrence Score (RS). Women with a Low RS of 0-10 received endocrine therapy alone and those with a High RS of 26-100 received endocrine therapy in combination with standard adjuvant chemotherapy which included T-AC (Taxane usually Docetaxel along with anthracycline usually Doxorubicin plus Cyclophosphamide, or TC (Taxane plus Cyclophosphamide, but without an anthracycline). Patient with Intermediate RS of 11-25 (N=6711) were randomly assigned to receive endocrine therapy alone (N=3399) or endocrine therapy and adjuvant chemotherapy (N=3312).TAILORx study concluded that among patients with a Recurrence Score of 11-25, endocrine therapy alone was non-inferior to chemotherapy plus endocrine therapy.
A subset of 2,591 patients, who had a recurrence score between 11 and 100, formed the basis for this analysis. Among them, 437 patients received T-AC, while 2,091 received TC regimen. Outcomes were compared between patients who received T-AC and those who received TC, adjusting for key variables such as age, RS, tumor size, grade, and Estrogen/Progesterone Receptor status. Outcomes were stratified by RS > 31 and < 31.The study population had a median age of 55 years, and median follow up was 7.3 years. The Primary end point of this study was to evaluate Distant Recurrence-Free Interval (DRFI). Other outcomes included Recurrence-Free Survival (RFS) and Overall Survival (OS).
Impact of Recurrence Score
This analysis revealed that the addition of anthracyclines to chemotherapy provided distinct benefits for patients with a high RS, specifically those with an RS of 31 or higher. Among this high risk group, the 5-year Distant Recurrence-Free Interval (DRFI) was significantly improved with T-AC compared to TC (adjusted DRFI rate was 97.5% for T-AC versus 89.4% for TC (adjusted HR=0.27, P=0.01). Similarly, Distant Recurrence-Free Survival (DRFS) was 96.5% for T-AC versus 88.3% for TC (adjusted HR=0.45, P= 0.03), and Recurrence-Free Survival (RFS) was also superior with T-AC. There was a trend towards improved OS at 5 years. For patients with an RS of less than 31, no significant benefit was observed from the addition of anthracyclines. This was particularly true for patients with an RS between 26 and 30, where no clear advantage of T-AC over TC was seen. In these lower-risk patients, both the DRFI and DRFS were similar between the two regimens.
The benefit of T-AC over TC increased further for higher RS values indicating that patients with higher recurrence scores saw more significant benefits from the addition of anthracyclines (HR=0.60 for RS 40 and HR=0.45 for RS 50).
Effect of Tumor Size
The benefit of T-AC in high-risk patients was particularly pronounced in tumors larger than 2 cm. While the primary endpoint of DRFI showed improvement with T-AC when the recurrence score was higher than 31regardless of tumor size, secondary endpoints, including DRFS, were notably enhanced in patients with tumors above the 2 cm size threshold. In contrast, smaller tumors (2 cm or less) did not demonstrate a benefit from the addition of anthracyclines.
Effect in Premenopausal and Postmenopausal Patients
Both premenopausal and postmenopausal patients with high RS showed a benefit from the addition of anthracyclines to chemotherapy. The DRFI advantage was seen in both groups, with statistical significance for premenopausal patients (P=0.032) and a trend toward significance for postmenopausal patients (P=0.028).
Risk of Non-Breast Cancer Deaths
An important consideration when making treatment decisions are the potential risks associated with anthracycline use, especially long-term risks such as leukemia or other non-breast cancer deaths.
In conclusion, the TAILORx analysis suggests that for patients with early stage, HR-positive/HER2-negative breast cancer, OncotypeDX Recurrence Score appears to be a reliable predictor of which patients might benefit from anthracyclines. Patients with a high recurrence score (RS 31 or more) derived significant benefit from the addition of anthracyclines to chemotherapy, especially those with tumors larger than 2 cm. The study was a post-hoc analysis of the TAILORx trial, which was not specifically designed to evaluate the benefit of anthracyclines and must be interpreted with caution pending further validation in prospective trials.
Impact of Anthracyclines in High Genomic Risk Node-Negative HR+/HER2- Breast Cancer. Chen N, et al. Abstract GS3-03. Presented at: San Antonio Breast Cancer Symposium; Dec. 10-13, 2024; San Antonio, TX. Abstract GS3-03
