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Clinical trial looks at combining cancer vaccine and chemotherapy for metastatic breast cancer patients

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A phase II clinical trial has looked at whether metastatic breast cancer patients improve after receiving a combination of chemotherapy and an experimental cancer vaccine. While the results of the trial show a trend towards longer time without their cancer progressing, a larger clinical trial needs to be done to confirm this finding.

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This study is about:

A clinical trial comparing the combination of PANVAC, an experimental cancer vaccine, and chemotherapy with docetaxel to the cancer vaccine alone in people with metastatic breast cancer (cancer that has spread beyond the breast and local lymph nodes to other organs in the body).  PANVAC has undergone clinical trials for patients with breast, ovarian, and colorectal cancer but has not been approved as a treatment.  

Why is this study important?  

This study is looking at a potential new treatment for metastatic breast cancer patients. When used alone, cancer vaccines have not been shown to improve patients’ progression-free survival (PFS). PFS is the amount of time a patient lives with the diseases without the disease getting worse.  The researchers reasoned that using docetaxel, a standard chemotherapy for metastatic breast cancer, in combination with the experimental cancer vaccine PANVAC would improve PFS by giving the patient time for the vaccine to take effect. 

Study finding: 

There is a trend towards increased progression-free survival for women who got both the cancer vaccine and chemotherapy compared to the women who got chemotherapy alone.

What does this mean for me?  

While researchers found a trend towards improved progression-free survival with both the vaccine and chemotherapy, the results were not statistically significant. However, promising results from this clinical trial justify designing a larger study using a similar combination of treatments to provide more answers about whether this combination can improve survival in people with metastatic breast cancer.

Questions to ask your health care provider:

  • How can I get involved in a clinical trial?


Study background:

This is a randomized phase II clinical trial. Phase II clinical trials are conducted to determine the effectiveness of a treatment and to evaluate its safety.

Researchers of this study wanted to know:

Whether the combination of the experimental cancer vaccine (PANVAC) and the approved chemotherapy docetaxel improves progression-free survival for metastatic breast cancer patients.  

Population(s) looked at in the study:

The study included 48 participants.

  • All had metastatic breast cancer—cancer that has spread beyond the breast and local lymph nodes to other organs.
  • The patients did not have active brain metastases.
  • Participants were either from the National Cancer Institute (NCI) or the University of Texas MD Anderson Cancer Center (MDACC).

In this phase II trial, 25 patients received both the cancer vaccine and chemotherapy, while 23 other patients received chemotherapy alone.

Study findings: 

  1. The median progression-free survival (PFS) for patients who received both the cancer vaccine and chemotherapy was approximately 8 months, while the median PFS for patients who received chemotherapy alone was approximately 4 months. These results are not statistically significant.


The number of participants in this study was small, which is why although there was an improvement in progression-free survival, we cannot conclude with certainty that it can be attributed to the combination of vaccine and chemotherapy treatments. Additionally, the study included patients with metastatic breast cancer of any subtype (ER/PR+, triple negative, HER2+), who had received any previous treatment except docetaxel.

Further complicating this study, metastatic breast cancer patients who received the vaccine at the National Cancer Institute were also given GM-CSF (granulocyte-macrophage colony-stimulating factor), which improves white blood cell recovery after treatment, while participants at the University of Texas MD Anderson Cancer Center did not. Because not all patients received GM-CSF, and data on the effect and effectiveness of administering GM-CSF with vaccines was mixed, it may have had an unknown effect on the study results.


As a phase II study, this study was designed to only detect improvement in progression-free survival (PFS) and to guide the design of a larger clinical trial. So while the researchers did find what they were looking for (a trend for improved PFS), the only conclusion they can draw is that a larger, more specified clinical trial is needed to determine the true effect of the combination of cancer vaccine and chemotherapy on patients with metastatic breast cancer.  


Heery CR, Ibrahim NK, Arlen PM et al. “Docetaxel Alone or in Combination With a Therapeutic Cancer Vaccine (PANVAC) in Patients with Metastatic Breast Cancer: A Randomized Clinical Trial.” JAMA Oncology, published online first on August 20th, 2015.

Posted 10/27/15

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