Study Suggests Biweekly Treatment May Be Better For TNBC

Breast Cancer News
February 26, 2015
Erin Rowley, Writer and Content Coordinator
Reviewed By: 
Virginia Kaklamani, MD, DSc

Researchers with the Southwest Oncologyinfo-icon Group (SWOG) S0221 clinical trialinfo-icon gave similar chemotherapyinfo-icon treatments to people with high-risk, early-stage breast cancerinfo-icon. But they assigned some people to daily and weekly treatment, and others to treatment once every 2 weeks, or biweekly. They found that, overall, no treatment schedule stopped cancer from returning better than the other. However, a sub-analysis suggested people with triple-negative breast cancerinfo-icon did better with a biweekly schedule than with a daily and weekly schedule.

Background and Goals

Doxorubicininfo-icon (Adriamycin) is a member of a group of chemotherapy medicines called anthracyclinesCyclophosphamideinfo-icon (Cytoxaninfo-icon) is an alkylating agentDoxorubicin and cyclophosphamide are often given together and called an AC regimeninfo-icon. It is most often given after surgeryinfo-icon, every 2 or 3 weeks.

Paclitaxelinfo-icon (Taxolinfo-icon) is a member of a group of chemotherapy medicines called taxanes. They are often given after treatment with doxorubicin and cyclophosphamide.

Creating new medicines is an important part of breast cancer research. But researchers with the SWOG S0221 clinical trial also felt it was important to look at existing medicines. They wanted to see if giving the medicines more often would help people with high-risk, early-stage breast cancer avoid recurrenceinfo-icon, or return of cancer.

Previously released results from this study showed that weekly and biweekly paclitaxel worked equally well. But fewer side effects were seen in the weekly group than in the biweekly group. Both treatment schedules are regularly used in the U.S.


More than 2,700 people with high-risk, early-stage breast cancer took part in this trial. The cancer was considered high-risk if it affected the lymphinfo-icon nodes near the breast, small organs that help the body remove waste, bacteria or damaged cells. It was also high-risk if the main tumorinfo-icon was 2 centimeters or bigger, or if any tumor was triple-negative AND 1 centimeter or bigger.

Participants were assigned to one of two doxorubicin and cyclophosphamide schedules:

  • Standard Biweekly Plan: Every 2 weeks for a total of 6 cycles given over 12 weeks
    • Doxorubicin and cyclophosphamide, by IV, on day 1
    • pegfilgrastim (Neulasta), which helps the body make more white blood cells, by injectioninfo-icon, on day 2
  • Study Treatment Plan: For 15 weeks
    • doxorubicin, by IV, once per week
    • cyclophosphamide, by mouth, once per day
    • filgrastim (Neupogen), which helps the body make more white blood cells, by injection, once per day, except on days that the doxorubicin was given

After completing their AC treatment, participants were then randomly given paclitaxel on one of two schedules:

  • on day 1, plus pegfilgrastim on day 2, once every 2 weeks for 12 weeks
  • once a week for 12 weeks

The researchers focused on how the medicines affected disease-free survival, DFS, the time from starting the study treatment to recurrence, new breast cancer or death from any cause. They also looked at overall survival, OS, the time from starting the study treatment to death from any cause.


After a medianinfo-icon 6 years of follow-up, the researchers found no significant difference in DFS no matter which AC regimen the participants used.

However, after looking at the data by breast cancer subtype, they found that OS was highest in those who had triple-negative breast cancer and were in the biweekly AC and biweekly paclitaxel treatment group.

They also found that

  • more people on the daily/weekly study plan stopped treatment early
  • there were more side effects in the daily/weekly group

What This Means for You

If you have triple-negative breast cancer, it may be comforting to hear that taking both of these standard medicines biweekly may positively impact your treatment. The researchers recommend more studies explore biweekly treatment to find out more. If you are taking or plan to take paclitaxel weekly and are curious about taking it biweekly, talk to your doctor about why he or she recommends one schedule or the other.

These researchers hoped giving existing breast cancer medicines more often would prevent more recurrences and deaths. Unfortunately, they learned that, for most people, the new AC regimen worked about as well as the standard regimeninfo-icon, but with more side effects.

Since no treatment plan lengthened DFS better than any other, the researchers recommend doctors give these medicines based on expected side effects, cost and your preferences.

To learn about participating in studies like this, visit To learn more about what breast cancer medicines are available to you, read our Guide to Understanding Treatment Decisions.

Budd, George T.; Barlow, William E.; Moore, Halle C.F. et al. SWOG S0221: A Phase III Trial Comparing Chemotherapy Schedules in High-Risk Early-Stage Breast CancerJournal of Clinicalinfo-icon Oncology. Published online ahead of print on November 24, 2014; doi: 10.1200/JCO.2014.56.3296.

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