Injection of a new gene therapy into breast tumors, in combination with chemotherapy, shows impressive therapeutic effects in locally advanced breast cancers, according to the results of a preliminary new study.

The gene therapy, called Advexin, is made by Introgen Therapeutics and contains the naturally occurring human form of a tumor suppressor gene called p53, Dr. Massimo Cristofanilli from The M. D. Anderson Cancer Center in Houston told participants at the 27th annual San Antonio Breast Cancer Symposium on Wednesday.

The chemotherapy treatment included the drugs docetaxel and doxorubicin.

About half of all women with locally advanced breast cancer have mutations in the tumor suppressor gene p53, Cristofanilli explained in a telephone interview with Reuters Health. Advexin therapy uses a virus to shuttle high concentrations of normal p53 to breast tumors.

In the current study, 12 women with locally advanced breast cancer (stage IIIB) received up to six cycles of Advexin injections plus chemotherapy before they underwent surgery. This treatment led to a greater than 50 percent reduction in tumor size, from an average of 8 centimeters to 1.78 centimeters, in all of the women.

“Every patient who received Advexin plus chemotherapy responded to the treatment; and this is an uncommon finding with locally advanced disease,” Cristofanilli said.

Examination of the breast tumors after removal showed significant infiltration of T-lymphocytes, a type of white blood cell, suggesting that Advexin produced an extensive immunological local response in the breast, Cristofanilli reported. “This is obviously a finding that is quite new for a local treatment for the breast, and we think this constitutes actually the benefit of the treatment itself,” he said.

The investigators also observed an increase in p53 RNA with Advexin therapy indicating, “this therapy is producing biologically what we expect it to,” Dr. Cristofanilli noted.

The next step will be to determine “how superior Advexin plus chemotherapy is to chemotherapy alone,” Dr. Cristofanilli said. “Based on the fact that we have only one death so far, and we are approaching 28 months of follow-up, I would say that this appears to be very promising.”

If a 75 percent to 85 percent survival rate after five years is achieved, he noted, “obviously this is much superior to what we can see with chemotherapy.”