Metastatic breast cancer is breast cancer that has spread beyond the breast area to other places in the body, such as the bones, lungs, liver, or brain. Metastatic breast cancer is considered advanced-stage disease.
Researchers wanted to know if an experimental chemotherapy medicine, called S-1, offered the same benefits as taxane chemotherapy medicines as the first chemotherapy treatment for metastatic, HER2-negative breast cancer. The results showed that women who were treated with S-1 had the same overall survival as women who were treated with a taxane.
The study was published in the January 2016 issue of The Lancet Oncology. Read the abstract of “Taxanes versus S-1 as the first-line chemotherapy for metastatic breast cancer (SELECT BC): an open-label, non-inferiority, randomized phase 3 trial.”
S-1 belongs to a class of chemotherapy medicines called antimetabolites. Xeloda (chemical name: capecitabine), fluorouracil, Gemzar (chemical name: gemcitabine), and methotrexate are other antimetabolites. Antimetabolities kill cancer cells by acting as false building blocks in a cancer cells’ genes, causing the cancer cell to die as it gets ready to divide.
S-1 is a pill taken by mouth.
Taxane chemotherapy medicines are:
- Taxol (chemical name: paclitaxel)
- Taxotere (chemical name: docetaxel)
- Abraxane (chemical name: albumin-bound or nab-paclitaxel)
Taxanes work by interfering with the ability of cancer cells to divide.
All the taxanes are given intravenously.
In this Japanese study, 618 women diagnosed with metastatic, HER2-negative breast cancer that hadn’t been treated with chemotherapy yet were randomly assigned to get either:
- taxane chemotherapy (309 women)
- S-1 chemotherapy (309 women)
The researchers analyzed results from 286 women who were treated with taxane chemotherapy and 306 women treated with S-1 chemotherapy. The women were followed for about 3 years.
Median overall survival was:
- 35 months for women treated with S-1
- 37.2 months for women treated with a taxane
Overall survival is how long the women lived, whether or not the cancer grew. Median overall survival means half the women lived longer than that amount of time and half the women lived for less than that amount of time.
The most common side effects were:
- neutropenia (low white blood cell count) -- 7% of women treated with S-1 and 3% of women treated with a taxane had neutropenia
- fatigue -- 3% of women treated with S-1 and 4% of women treated with a taxane had fatigue
- fluid retention -- less than 1% of women treated with S-1 and 4% of women treated with a taxane had fluid retention
The researchers concluded that S-1 offered the same overall survival benefits as the taxanes and should be considered a new option as the first chemotherapy to treat HER2-negative, metastatic breast cancer.
If you’ve been diagnosed with HER2-negative, metastatic breast cancer that hasn’t yet been treated with chemotherapy, you might want to talk to your doctor about this study. If you’re willing to participate in the clinical trial, you may have the option of being treated with S-1. Talk to your doctor about clinical trials that may be a good fit for you. You can visit the Breastcancer.org Clinical Trial pages for more information.
And stay tuned to Breastcancer.org’s Research News for the latest information on new treatments for metastatic breast cancer.
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