New England Journal of Medicine December 01, 2021

21-Gene Assay to Inform Chemotherapy Benefit in Node-Positive Breast Cancer

Kevin Kalinsky, William E. Barlow, Julie R. Gralow, et al.

Bottom Line

In women with HR-positive, HER2-negative breast cancer with 1 to 3 positive lymph nodes and an Oncotype DX Recurrence Score of 0 to 25, adjuvant chemotherapy significantly improved invasive disease-free survival in premenopausal women, but provided no benefit to postmenopausal women.

Key Findings

1. At a median follow-up of 5.3 years, premenopausal women receiving chemoendocrine therapy had a significantly higher 5-year invasive disease-free survival (94.2%) compared to those receiving endocrine therapy alone (89.0%), representing an absolute benefit of 5.2 percentage points (HR 0.60; 95% CI, 0.43 to 0.83).

2. Among postmenopausal women, 5-year invasive disease-free survival was equivalent between the chemoendocrine arm (91.6%) and the endocrine-only arm (91.9%), with a hazard ratio of 0.97 (95% CI, 0.78 to 1.22), confirming no benefit from added chemotherapy.

3. There was a highly significant interaction between menopausal status and chemotherapy benefit (P=0.008).

4. In premenopausal women, the relative benefit of chemotherapy did not progressively increase with higher recurrence scores; rather, the hazard ratio remained consistent across the 0-25 range.

Study Design

Design

Randomized Controlled Trial

Open-Label

Sample

5,018

Patients

Duration

5.3 yr

Median

Setting

Multicenter, International

Population Women with early-stage, HR-positive, HER2-negative breast cancer involving 1 to 3 axillary lymph nodes and an Oncotype DX Recurrence Score of 25 or lower.

Intervention Adjuvant chemotherapy containing a taxane and/or anthracycline, followed by standard endocrine therapy.

Comparator Adjuvant standard endocrine therapy alone.

Outcome Invasive disease-free survival (IDFS).

Study Limitations

• The biological mechanism driving the chemotherapy benefit in premenopausal women remains ambiguous; it is unclear if it stems from direct cytotoxic tumor eradication or secondary chemotherapy-induced ovarian function suppression (OFS).

• Only 16% of premenopausal women in the endocrine-alone arm underwent active ovarian function suppression, leaving it unknown whether optimal endocrine therapy with OFS would have matched the efficacy of chemotherapy.

• The median follow-up of 5.3 years is relatively short for HR-positive, HER2-negative breast cancer, which is characterized by a steady risk of late distant recurrences over 10 to 20 years.

• The trial safely excluded patients with 4 or more positive lymph nodes, meaning the findings cannot be extrapolated to this higher-risk population where adjuvant chemotherapy remains standard.

Clinical Significance

RxPONDER transformed clinical guidelines for early-stage, node-positive breast cancer. It definitively established that postmenopausal women with 1 to 3 positive lymph nodes and an Oncotype DX recurrence score of 0 to 25 can safely omit adjuvant chemotherapy, sparing approximately two-thirds of this population from severe cytotoxic toxicities. Conversely, it reaffirmed that premenopausal women in the same genomic and nodal risk cohort derive a substantial survival benefit from chemotherapy, cementing chemoendocrine therapy as their standard of care until future trials evaluate whether ovarian function suppression can safely replace it.

Historical Context

Prior to RxPONDER, the landmark TAILORx trial proved that the 21-gene recurrence score could successfully identify node-negative, HR-positive breast cancer patients who could safely omit chemotherapy. However, because nodal involvement inherently increases clinical recurrence risk, patients with node-positive disease were historically treated with aggressive adjuvant chemotherapy regardless of tumor genomics. The SWOG S1007 (RxPONDER) trial was designed to evaluate whether the genomic precision medicine paradigm could be extended to patients with limited nodal involvement (1-3 positive nodes), hypothesizing that a low genomic risk profile could predict a lack of chemotherapy benefit even in node-positive disease.

Guided Discussion

High-yield insights from every perspective

Med Student

Medical Student

What is the biological rationale for using the 21-gene recurrence score (Oncotype DX) to guide chemotherapy decisions in estrogen receptor-positive breast cancer?

Key Response

The Oncotype DX assay measures the expression of 21 genes involved in proliferation, estrogen signaling, and HER2 pathways. In HR-positive, HER2-negative breast cancers, highly proliferative tumors with higher scores are more likely to respond to cytotoxic chemotherapy, which targets rapidly dividing cells. Conversely, low-score tumors are driven primarily by estrogen signaling and derive more benefit from endocrine therapy alone, sparing the patient chemotherapy toxicity.

Resident

A 55-year-old postmenopausal woman presents with HR-positive, HER2-negative breast cancer with 2 positive axillary lymph nodes and a Recurrence Score of 18. Based on the RxPONDER trial, what is the most appropriate systemic adjuvant therapy?

Key Response

Endocrine therapy alone. Prior to RxPONDER, patients with any node-positive disease were often reflexively offered chemotherapy. This trial demonstrated that postmenopausal women with 1 to 3 positive nodes and a Recurrence Score of 0 to 25 derive no invasive disease-free survival benefit from the addition of chemotherapy. Thus, she can safely avoid chemotherapy and its associated toxicities, proceeding directly to aromatase inhibitor therapy.

Fellow

In the RxPONDER trial, premenopausal women with a Recurrence Score of 0 to 25 experienced an invasive disease-free survival benefit from chemotherapy. How does the hypothesis of chemotherapy-induced ovarian function suppression complicate the interpretation of a direct cytotoxic benefit in this subgroup?

Key Response

The chemotherapy benefit in premenopausal women could be largely due to ovarian suppression caused by the chemotherapy itself, rather than a direct cytotoxic effect on micrometastases. Since trials like SOFT and TEXT demonstrated the profound benefit of ovarian function suppression in high-risk premenopausal women, it is debated whether combining GnRH agonists with standard endocrine therapy might achieve the same RxPONDER benefit without the risks of chemotherapy.

Attending

How should we counsel premenopausal patients with 1 to 3 positive nodes and a low Recurrence Score about the choice between chemotherapy versus aggressive endocrine therapy with ovarian suppression?

Key Response

RxPONDER established chemotherapy followed by endocrine therapy as the standard of care for premenopausal women with 1 to 3 positive nodes and a Recurrence Score of 0 to 25, showing a clear absolute benefit. However, because the trial did not mandate ovarian function suppression in the endocrine-alone arm, we cannot definitively tell a patient that ovarian suppression plus an aromatase inhibitor is equivalent to chemotherapy. Shared decision-making is essential, but the evidence-based recommendation remains chemotherapy.

Scholarly Review

Critical appraisal through the lens of expert reviewers and guideline development

PhD

The RxPONDER trial utilized invasive disease-free survival as its primary endpoint. What are the statistical and clinical tradeoffs of using this endpoint versus overall survival in a trial involving HR-positive, HER2-negative breast cancer with an anticipated low event rate?

Key Response

Using invasive disease-free survival allows the trial to read out much earlier than overall survival, given the long natural history and late recurrences typical of HR-positive breast cancer. However, this endpoint includes events like contralateral breast cancers and non-breast primary cancers, which may dilute the signal of the chemotherapy intervention. Furthermore, the low overall event rate reduces the statistical power to detect small overall survival differences, making it difficult to confirm if the benefit in premenopausal women translates to a mortality reduction.

Journal Editor

A significant critique of the RxPONDER trial relates to the variable use of ovarian function suppression in the control arm for premenopausal women. How does this confounding variable threaten the internal validity of the study conclusions regarding the premenopausal cohort?

Key Response

In the endocrine-alone arm, only about 16 percent of premenopausal women received ovarian function suppression. Because this suppression is highly effective in this population, the control arm may have been under-treated compared to modern optimal standards. This disparity introduces a major confounding factor: the apparent superiority of the chemotherapy arm might merely reflect the unmasking of suboptimal endocrine therapy in the control arm rather than a true need for cytotoxic therapy.

Guideline Committee

Based on the findings from RxPONDER, how should NCCN and ASCO guidelines formulate recommendations regarding genomic assay testing and chemotherapy in node-positive early-stage breast cancer?

Key Response

NCCN and ASCO guidelines should strongly recommend 21-gene recurrence score testing for patients with 1 to 3 positive lymph nodes. Based on Level 1 evidence from RxPONDER, guidelines must state that for postmenopausal women with 1 to 3 positive nodes and a Recurrence Score of 0 to 25, chemotherapy is not recommended. For premenopausal women with the same nodal status and score, chemotherapy is recommended due to the proven survival benefit, representing a major paradigm shift away from a strictly anatomical staging approach to a combined clinico-genomic algorithm.

Clinical Landscape

Noteworthy Related Trials

2010

SWOG S8814

n = 367 · Lancet Oncol

Tested

CAF chemotherapy plus tamoxifen

Population

Postmenopausal women with node-positive, ER-positive breast cancer

Comparator

Tamoxifen alone

Endpoint

Disease-free survival

Key result: The 21-gene recurrence score was highly prognostic, and only patients with a high recurrence score benefited from the addition of chemotherapy.

2016

MINDACT

n = 6,693 · NEJM

Tested

Chemotherapy omission based on 70-gene signature (MammaPrint)

Population

Women with early-stage breast cancer and high clinical but low genomic risk

Comparator

Chemotherapy administration based on clinical risk

Endpoint

5-year distant metastasis-free survival

Key result: Among patients with high clinical risk and low genomic risk, the rate of survival without distant metastasis was 94.7% without chemotherapy.

2018

TAILORx

n = 10,273 · NEJM

Tested

Endocrine therapy alone

Population

HR-positive, HER2-negative, node-negative breast cancer with midrange recurrence score (11-25)

Comparator

Chemoendocrine therapy

Endpoint

Invasive disease-free survival

Key result: Endocrine therapy was noninferior to chemoendocrine therapy in patients with a recurrence score of 11 to 25, though some benefit was seen in women under 50.

Tailored to your role

Want this tailored to you?

Add your specialty or training stage to get role-specific takeaways and more questions.

Personalize this analysis