Luminal A breast cancer is cancer that is estrogen-receptor positive and/or progesterone-receptor positive, HER2-negative, and has low levels of the protein Ki-67, which helps control how fast cancer cells grow.
A study has found that premenopausal women diagnosed with luminal A breast cancer had the same disease-free survival rates whether or not they were treated with chemotherapy after breast cancer surgery. This means that chemotherapy offered no benefits to these women.
The research, “High risk premenopausal luminal A breast cancer patients derive no benefit from adjuvant chemotherapy: Results from DBCG77B randomized trial,” (Abstract S1-08) was presented on Dec. 9, 2015 at the 2015 San Antonio Breast Cancer Symposium.
Disease-free survival is how long a woman lives without the cancer coming back (recurrence).
Treatments given after surgery for breast cancer are called adjuvant treatments. Adjuvant treatments are given to destroy any cancer cells that may have been left behind after surgery, making recurrence less likely.
“Luminal A is a relatively common subtype of breast cancer,” said Torsten Nielsen, M.D., Ph.D., professor of pathology at the University of British Columbia. “It is the form of breast cancer with the best prognosis.
“We wanted to address the clinical question of whether or not women with molecularly low-risk luminal A breast cancer actually benefit from chemotherapy,” he continued. “Instead of starting a new trial and waiting for 10 years to find answers, we used an older, completed trial that had saved tissue samples for future studies.”
To do this study, Dr. Nielsen and his colleagues analyzed tissue samples from 709 premenopausal women who were part of the Dutch Breast Cancer Cooperative Group (DBCG) 77B trial. All the women were diagnosed with what was considered high-risk disease: the cancers were large, grade 3, and had spread to one or more lymph nodes. The study was done in the 1970s and 1980s -- before modern chemotherapy and hormonal therapy regimens had been well-established.
The researchers found that 165 of the samples were luminal A breast cancer.
In the DBCG77B trial, the women were randomly assigned to receive either:
- Cytoxan (chemical name: cyclophosphamide) chemotherapy
- a combination of Cytoxan, methotrexate, fluorouracil chemotherapy
- no chemotherapy
All the women also were treated with radiation therapy. None of the women were treated with hormonal therapy, even though some of the cancers were hormone-receptor positive.
The researchers found there were no differences in 10-year disease-free survival rates between women diagnosed with luminal A breast cancer who got chemotherapy and women who didn’t get chemotherapy.
Women who were diagnosed with one of the other subtypes of breast cancer who were treated with chemotherapy were 50% less likely to have a recurrence after 10 years than women who weren’t treated with chemotherapy.
The other subtypes of breast cancer are:
- luminal B: estrogen-receptor positive and/or progesterone-receptor positive and either HER2-positive, or HER2-negative with high levels of ki-67
- triple negative/basal-like: estrogen-receptor negative, progesterone-receptor negative, and HER2-negative
- HER2-enriched: estrogen-receptor negative, progesterone-receptor negative, and HER2-positive
Dr. Nielsen explained that because none of the women in the study were treated with hormonal therapy after surgery, even though luminal A breast cancer is hormone-receptor positive, the treatment in the study doesn’t reflect the current standard of care. Still, he also explained that hormonal therapy is known to make cancers less susceptible to chemotherapy.
“Given that women with luminal A subtype of breast cancer did not benefit from chemotherapy in our study, it would certainly be expected that women with similar tumor characteristics getting [hormonal] therapy would also receive no benefit from chemotherapy,” Dr. Neilsen said.
It’s important to know that the tissue samples for this study were collected before the Oncotype DX test and other genomic assays were created. The Oncotype DX test analyzes the activity of a group of genes that can affect how a cancer is likely to behave and respond to treatment. It’s used to help doctors figure out a woman’s risk of recurrence of early-stage, estrogen-receptor-positive breast cancer, as well as how likely she is to benefit from chemotherapy after surgery.
The Oncotype DX test results assign a Recurrence Score -- a number between 0 and 100 -- to the cancer:
- Recurrence Score lower than 18: The cancer has a low risk of recurrence. The benefit of chemotherapy is likely to be small and will not outweigh the risks of side effects.
- Recurrence Score of 18 up to and including 30: The cancer has an intermediate risk of recurrence. It’s unclear whether the benefits of chemotherapy outweigh the risks of side effects.
- Recurrence Score greater than or equal to 31: The cancer has a high risk of recurrence, and the benefits of chemotherapy are likely to be greater than the risks of side effects.
Dr. Neilsen and his colleagues plan to do Oncotype DX testing on the tumor samples to see if the cancers had a low Recurrence Score. If this is the case, then it makes sense that there were no chemotherapy benefits.
If you’re a premenopausal woman who has been diagnosed with luminal A breast cancer, the results of this study suggest that it’s possible you might not benefit from chemotherapy, even if the cancer is considered aggressive. If you can’t tolerate or would prefer not to have chemotherapy, the results of this study may offer some reassurance.
You and your doctor will consider a number of factors when deciding on a treatment plan after surgery, including:
- your age
- your menopausal status
- the size of the cancer
- cancer grade
- Oncotype DX or other genomic test results
- any other health issues you have
- your preferences
Together, you will develop a treatment plan that is right for you and your unique situation.
Read more Research News from the 2015 San Antonio Breast Cancer Symposium:
- Treating Residual Disease With Xeloda Improves Survival in Women With Early-Stage, HER2-Negative Disease
- Kadcyla Improves Survival in Women Diagnosed With Metastatic, HER2-Positive Disease That’s Stopped Responding to Herceptin and Tykerb
- Arimidex or Tamoxifen Reduce Recurrence Risk After DCIS Equally Well in Postmenopausal Women, Choice Depends on Age, Side Effects
- Lumpectomy Plus Radiation May Offer Survival Benefits for Early-Stage Disease
- Prolia Reduces Recurrence Risk of Hormone-Receptor-Positive Disease in Women Taking Aromatase Inhibitors
- Triple-Negative Disease May Have New Treatment Option