Clinical evidence for the Oncotype DX® test in node-positive patients

The retrospective analysis of the SWOG-8814 trial, in which HR+, node-positive, postmenopausal patients were randomised to chemoendocrine therapy vs endocrine therapy alone, established that the Recurrence Score result is predictive of chemotherapy benefit in node-positive patients¹, consistent with the findings in the node-negative setting in the NSABP B-20 clinical trial.^4-5

The Recurrence Score^® result was a predictive factor of chemotherapy benefit for disease-free survival (P interaction = 0.029), overall survival and breast cancer-specific survival in the first five years.¹

RxPONDER (SWOG S1007) is a prospective, randomised trial to determine the effect of chemotherapy in patients with hormone receptor-positive (HR+), HER2-negative breast cancer with 1-3 positive axillary lymph nodes. For this purpose, eligible patients with Recurrence Score^® (RS^®) results 0-25 were randomised to adjuvant chemotherapy followed by endocrine therapy or to endocrine therapy alone³.

RxPONDER study design: node-positive (1-3 nodes) patients with Recurrence Score results 0–25 were randomised to endocrine therapy alone or chemoendocrine therapy³

At a prespecified interim analysis in September 2020, the Data Safety Monitoring Committee advised the study investigators to report the available findings of the clinical trial. Preliminary results were presented at the San Antonio Breast Cancer Symposium on 10 December 2020³. A total of 5,015 patients were included in the analysis with a 5.1-year median follow up.

Postmenopausal patients

Stratified by menopausal status, 5-year invasive disease-free survival (IDFS) was similar for postmenopausal patients treated with endocrine therapy with or without chemotherapy (hazard ratio 0.97; 95% CI 0.78 to 1.22; p=.82)³. The lack of benefit from chemotherapy was observed regardless of clinicopathological factors such as patient age, tumour grade, tumour size, number of positive nodes, type of surgery, or Recurrence Score group (RS results 0-13 vs results 14-25)³. No significant difference in overall survival (OS) was observed (5-year OS 96.2% for CET vs 96.1% for ET; hazard ratio 0.96; 95% CI: 0.70-1.31; p=.79).³

Based on this interim analysis, the authors concluded that the majority of N1 postmenopausal patients do not benefit from adjuvant chemotherapy, independent of clinical pathological parameters and thus can likely forgo adjuvant chemotherapy without compromising IDFS based on Recurrence Score® results 0-25.³

N1 postmenopausal patients with RS® results 0-25 did not benefit from the addition of chemotherapy to endocrine therapy on any endpoint reported³

Premenopausal patients

For premenopausal patients, 5-year invasive disease-free survival (IDFS) differed significantly by treatment (chemotherapy hazard ratio 0.54; 95% CI 0.38 to 0.76; p=.0004)³, with a 2.9% absolute difference in rate of distant recurrence as first site. The benefit of chemotherapy was observed regardless of clinicopathological factors such as patient age, tumour grade, tumour size, number of positive nodes, axillary surgery, or Recurrence Score group (RS results 0-13 vs RS results 14-25)³. Notably, 5-year overall survival (OS) was significantly greater in premenopausal patients treated with chemotherapy plus endocrine therapy vs endocrine therapy alone (98.6% vs 97.3%; hazard ratio 0.47; 95% CI: 0.24-0.94; p=.032).³

Based on this interim analysis, the authors suggested that premenopausal patients with N1 breast cancer and Recurrence Score results 0-25 do benefit significantly from adjuvant chemotherapy. Data for the secondary endpoints will be reported in the future.³

N1 premenopausal patients with RS® results 0-25 did significantly benefit from the addition of chemotherapy with a 2.9% benefit in terms of distant recurrence³

CET=chemo-endocrine therapy

CI=confidence interval

CT=chemotherapy

DDFS=distant-disease free survival

ER= Endocrine therapy

HER2–=human epidermal growth factor receptor 2 negative

HR+=hormone receptor positive

N+=node-positive

N0=node-negative

N1mi=lymph node micrometastases

N1=1–3 positive nodes

RS=Recurrence Score result

RxPONDER=Rx for Positive Node, Endocrine Responsive Breast Cancer

TAILORx=Trial Assigning IndividuaLized Options for Treatment (Rx)