This finding is expected to save "tens of thousands of postmenopausal women the time, expense and potentially harmful side effects that can be associated with chemotherapy infusions," said Dr. Kevin Kalinsky, with the Winship Cancer Institute of Emory University, in Atlanta, during a media briefing at the virtual 2020 San Antonio Breast Cancer Symposium (SABCS).
In contrast to postmenopausal women, premenopausal women with positive nodes do benefit significantly from chemotherapy, the results suggest.
The RxPONDER trial follows the "landmark" TAILORx trial, which demonstrated that postmenopausal women with lymph node-negative, HR-positive, HER2-negative breast cancer and recurrence scores of 25 or less on a genomic tumor tissue test (Oncotype DX) did not benefit from the addition of chemotherapy to hormone therapy compared with hormone therapy alone, Dr. Kalinksy explained.
But TAILORx left open the question of the most effective way to treat women diagnosed with more advanced breast cancer that has spread to the lymph nodes - a question addressed in RxPONDER, he said.
The RxPONDER trial enrolled more than 5,000 women with HR-positive, HER2-negative stage 2-3 breast cancer with one to three positive lymph nodes and an Oncotype DX recurrence score of 25 or lower.
Half were randomly allocated to endocrine therapy alone and half to endocrine therapy plus chemotherapy. Roughly two-thirds of the women were postmenopausal. All women were followed for a median of five years.
When evaluating the entire study population including both premenopausal and postmenopausal women, there was no association between chemotherapy benefit and low recurrence score values of less than 25.
However, there was a significant association between chemotherapy benefit and menopausal status.
In postmenopausal women with recurrence scores of 25 or lower, there was no difference in the five-year invasive-disease-free survival (IDFS) between women who received chemotherapy and those who did not (91.6% vs. 91.9%).
"The results clearly showed no benefit to adding chemotherapy to standard endocrine therapy in postmenopausal patients, despite having a positive node," Dr. Kent Osborne, SABCS co-director, commented during the briefing.
This emphasizes that "node positivity, while an important prognostic marker, is not a predictive marker of chemotherapy sensitivity," said Dr. Osborne, with Baylor College of Medicine, Houston.
Premenopausal women, however, did benefit from chemotherapy. In this group, IDFS at five years was significantly better with chemotherapy than without (94.2% vs. 89.0%) - a benefit seen regardless of recurrence risk score.
Premenopausal women also appeared to have a small overall survival benefit with chemotherapy at five years (98.6% vs. 97.3%), although the overall survival data should be considered early due to the limited number of events at the time of this interim analysis.
Commenting on the results, Dr. Charles L. Shapiro, director of Translational Breast Cancer Research, Icahn School of Medicine at Mount Sinai, told Reuters Health the RxPONDER trial is "practice-changing."
"The trial de-escalates treatment, sparing postmenopausal women with one to three positive nodes and Oncotype Dx recurrence scores 25 or less, adjuvant chemotherapy. Furthermore, it's a victory for most women who are long-term survivors of breast cancer without the late and long-term effects of adjuvant chemotherapy," he said by email.
That postmenopausal women with one to three positive axillary nodes could be spared chemotherapy is "a great advance, as these women would automatically receive adjuvant chemotherapy in the past," he added. "Knowing who does and does not benefit from adjuvant chemotherapy precisely is powerful information for the individual women and cannot be overemphasized."
"There are several caveats in the RxPONDER trial, as in all randomized trials," he noted.
"First, this was an interim analysis with half the number of events projected for the final analysis (410 events now versus 832 events for the final analysis). In estrogen receptor-positive, HER2-negative, or luminal breast cancers, more than 50% of recurrences occur after five years. Further follow-up in the trial for 15 years is planned," said Dr. Shapiro.
SOURCE: https://www.sabcs.org/ 2020 San Antonio Breast Cancer Symposium, presented December 9, 2020.
By Megan Brooks
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