More women with early-stage breast cancer may safely forgo chemotherapy, suggests an interim analysis that had a median follow-up of five years of the large-scale phase-s RxPONDER trial, presented at the San Antonio Breast Cancer Symposium (SABCS) 2020.
The investigators reported that adding chemotherapy to endocrine therapy did not improve outcomes for postmenopausal women with low-risk, node-positive, hormone receptor–positive (HR+), human epidermal growth factor receptor 2–negative (HER2-) breast cancer in comparison to endocrine therapy alone.The results are akin to those from the TAILORx trial. The results of that trial were first presented in 2018 and have changed practice for women with early-stage disease who have no lymph node involvement.
MedPage Today reported that invasive disease-free survival (iDFS) at 5 years was virtually identical whether patients received hormonal therapy alone (91.9%) or with chemotherapy (91.6%). In contrast, premenopausal women had significantly higher iDFS at 5 years with chemoendocrine therapy (94.2%) versus endocrine therapy only (89.0%, P=0.0004), Dr Kevin Kalinsky, of Emory University in Atlanta, reported at the virtual meeting.
The results in postmenopausal women, who accounted for about two thirds of the study population, drove the overall results, which also showed no chemotherapy benefit. Overall survival (OS) improved slightly but significantly in premenopausal women who received chemotherapy (1.3% absolute difference at 5 years) but not in postmenopausal women (96% with or without chemotherapy).
The results have immediate implications for thousands of older breast cancer patients, according to Kalinsky. "Postmenopausal women with one to three positive nodes and a recurrence score of 0 to 25 can likely safely forgo adjuvant chemotherapy without compromising invasive disease-free survival," he said during a press briefing prior to SABCS. "This will save tens of thousands of women the time, expense, and potentially harmful side effects that can be associated with chemotherapy infusions.
"Premenopausal women with positive nodes and recurrence score 0 to 25 likely significantly benefit from chemotherapy."
Kalinsky summarized findings from the multicenter, phase III, randomized RxPONDER trial, which investigated the role of adjuvant chemotherapy in genomically low-risk, node-positive early-stage cancer at low risk of recurrence, as defined by a score of ≤25 by the Oncotype DX 21-gene assay. The study extends a narrative started with the TAILORx trial, which showed that postmenopausal women with node-negative HR-positive breast cancer and a low risk of recurrence derived no benefit from chemotherapy whereas premenopausal women with a risk score of 16-25 might benefit from it.
"In the United States, about 20% of patients with nonmetastatic, hormone receptor-positive, HER2-negative breast cancer present with one to three positive lymph nodes," said Kalinsky. "It has been unclear whether the TAILORx results can be extrapolated to node-positive breast cancer."
RxPONDER included approximately 5,015 patients, all of whom had stage II-III, HR-positive breast cancer, one to three positive lymph nodes, and a recurrence score ≤25. Following surgery, they were randomized to standard endocrine therapy with or without chemotherapy. The primary endpoint was 5-year iDFS.
At a planned interim analysis (after about 50% of iDFS events), the data showed no significant benefit of chemotherapy in the overall population. Prespecified analyses by menopausal status showed the iDFS hazard was nearly halved among premenopausal women who received chemotherapy (HR 0.54, 95% CI 0.38-0.76). In the postmenopausal subgroup, the 5-year iDFS did not differ significantly between treatment arms (HR 0.97, 95% CI 0.78-1.22).
A small absolute difference in OS favored chemotherapy for premenopausal patients (HR 0.47, 95% CI 0.24-0.94, P=0.32). OS in the premenopausal patients was almost identical in the two treatment arms (96.2% with chemotherapy, 96.1% without).
The interim findings of the RxPONDER Trial are not yet available online.
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