A large clinical trial published in the New England Journal of Medicine found a group of breast cancer patients who can safely skip chemotherapy and only take endocrine therapy after breast cancer surgery.
A large clinical trial published in the New England Journal of Medicine found that postmenopausal women with hormone receptor (HR) positive, human epidermal growth factor receptor 2 (HER2) negative breast cancer that has spread to at least three lymph nodes and a 21-gene recurrence score (RS) of 25 or less can safely skip chemotherapy and only receive endocrine therapy following breast cancer surgery.
The first results from S1007, the RxPONDER study, were presented last December at the San Antonio Breast Cancer Symposium. The study was conducted by the SWOG Cancer Research Network, a cancer clinical trials group funded by the National Cancer Institute (NCI), a portion of the National Institutes of Health. Additional data and research have bolstered these conclusions.
The study led by SWOG investigator Dr. Kevin Kalinsky, a breast medical oncologist at Emory University’s Winship Cancer Institute, compared rates of invasive disease-free survival (IDFS) – the percentage of women who survived five years after treatment assignment without a recurrence of their cancer or a second invasive primary cancer – among patients enrolled in the study.
They found no clinically relevant or statistically significant improvement in IDFS for women who received chemotherapy followed by endocrine therapy compared to women who received endocrine therapy alone when they looked at the entire research cohort.
However, when they looked at just the premenopausal women, who made up about one-third of the study participants, a distinct difference revealed. When compared to premenopausal women who just received endocrine therapy, those who underwent chemotherapy saw a 40% improvement in IDFS. Women in the trial who were postmenopausal, on the other hand, did not benefit from chemotherapy.
“These are clinically meaningful and impactful data,” said Kalinsky.
“As we saw that postmenopausal women with one to three positive nodes and RS 0 to 25 can likely safely forego adjuvant chemotherapy without compromising IDFS, this will save tens of thousands of women the time, expense, and potentially harmful side effects that can be associated with chemotherapy. Premenopausal patients with positive nodes and RS 0 to 25, however, likely benefit from chemotherapy.”
The five-year IDFS rates for premenopausal patients who got endocrine therapy alone were 89.0 percent versus 93.9 percent for those who had combined chemotherapy and endocrine therapy. The five-year IDFS rates in postmenopausal patients were 91.9 percent versus 91.3 percent, a statistically insignificant difference.
The 21-gene recurrence score test determines a woman’s overall risk of breast cancer recurrence by measuring the expression level of a panel of 21 particular genes in tumor tissue. The scale runs from 0 to 100, with scores of 25 or less indicating a low or intermediate risk of recurrence.
At the time of diagnosis, disease had progressed to the lymph nodes in approximately one-third of women with HR+, HER2- breast cancer. These women’s cancers are known as node-positive disease, and they have a higher chance of recurrence after treatment.
A retrospective examination of data and biospecimens from a previous SWOG research, S8814, revealed that the 21-gene RS may be used to identify which women with these features would benefit from chemotherapy in addition to endocrine therapy. In that analysis, women with an RS of less than 18 received no benefit from chemotherapy, whereas those with an RS of at least 31 received benefit.
The RxPONDER trial was designed to determine conclusively if RS could be used to predict which women with HR+, HER-, or node-positive breast cancer would benefit from chemotherapy. The researchers enrolled 5,083 women with this malignancy with an RS of 25 or less at 632 sites in nine countries, randomly assigning half to undergo chemotherapy followed by endocrine therapy following surgery and the other half to receive endocrine therapy alone following surgery.
As a secondary goal, the team examined distant disease-free survival (DDFS) in these patients and discovered a 42 percent relative improvement in DDFS in premenopausal women but no difference in DDFS in postmenopausal women due to chemotherapy. DDFS is distinct from IDFS in that it considers only distant recurrence or death, not local or regional recurrence or new invasive primary malignancies.
Additional post-hoc studies published in the paper divided premenopausal women receiving chemotherapy into four groups based on their 21-gene RS – 10, 11, 15, 16, 20, and 21-25 – and assessed their IDFS five years following randomization. While the relative benefit of chemotherapy remained constant as the RS grew from 0 to 25, the absolute benefit was greater in patients with a higher RS.
Additionally, they discovered that premenopausal women aged 50 or younger who had the lowest RS scores benefited from chemotherapy in addition to endocrine therapy.
“These data further help individualize the discussion of risk and benefit of chemotherapy with premenopausal patients with up to three lymph nodes and an RS of 25 or less,” said Kalinsky.
Source: New England Journal of Medicine
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