Up to 85% of women with early ER-positive, HER2-negative, node-negative breast cancer can be spared chemotherapy, according to results presented at the 2018 American Society of Clinical Oncology (ASCO) Annual Meeting.

The TAILORx trial of more than 10,000 women found endocrine therapy alone was non-inferior to endocrine therapy plus chemotherapy in women with a midrange Oncotype DX Breast Recurrence Score of 11 to 25.

This group represent the majority of participants (69%) in the trial of more than 10,000 women.

The addition of chemotherapy did not improve invasive disease-free survival or secondary outcomes such as distant recurrence, local-regional recurrence or overall survival.

The findings clarify the interpretation of a midrange Recurrence Score.

High-risk women (RS≥ 26) are known to benefit from chemotherapy despite having poorer outcomes overall while low-risk women (RS ≤10) do not benefit from chemotherapy in addition to endocrine therapy.

However age does appear to mediate the likely benefit of chemotherapy.

Chief investigator Dr Joseph Sparano, from New York’s Montefiore Medical Center, told the meeting there was some benefit from chemotherapy in terms of lower rates of distant recurrence in the women aged 50 years or younger with mid-range recurrence scores.

The trial concluded that adjuvant chemotherapy may be spared in all women older than age 50 with an RS of 11 to 25.

“Application of this test in clinical practice in this population could be estimated to spare chemotherapy in 69% and to select chemotherapy in 31%, on average,” Dr Sparano concluded.

The trial, also published in the NEJM, said the use of adjuvant chemotherapy had decreased substantially on the basis of previous information regarding the utility of the Recurrence Score.

“The results of our trial suggested that the 21-gene assay may identify up to 85% of women with early breast cancer who can be spared adjuvant chemotherapy, especially those who are older than 50 year of age and have a recurrence score of 25 or lower, as well as women 50 years of age or younger with a recurrence score of 15 or lower,” it said.

Speaking at an ASCO press conference, Dr Harold Burstein from the Dana-Farber Cancer Institute, said that the vast majority of women who have the genomic test can be reassured that they don’t need chemotherapy.

“The goal of this study was not to just use less treatment. The goal was to tailor treatment. They chose the title very aptly, with the idea that some women are going to need more of some type of therapy and less of another, and others will get a different treatment based on the biology of their tumor.”