Experimental Iniparib Plus Chemo Can Help Treat Metastatic, Triple-Negative Disease

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A small study found that iniparib -- one of several new, experimental medicines called PARP inhibitors -- improved survival when combined with chemotherapy to treat metastatic, triple-negative breast cancer. The results were presented at the 2010 annual meeting of the European Society for Medical Oncology (ESMO).

Metastatic breast cancer is cancer that has spread to other parts of the body away from the breast, such as the bones or liver.

Triple-negative breast cancer is:

  • estrogen-receptor-negative
  • progesterone-receptor-negative
  • HER2-negative

About 15% to 20% of breast cancers are triple-negative. Triple-negative cancers are usually more aggressive, harder to treat, and more likely to come back (recur) than cancers that are hormone-receptor-positive and/or HER2-positive. Hormonal therapy and the targeted therapies Herceptin (chemical name: trastuzumab) and Tykerb (chemical name: lapatinib) usually don't work on triple-negative breast cancer.

Because triple-negative breast cancer is aggressive and there are a limited number of treatment choices, doctors are looking for new ways to treat it. They are looking at new combinations of standard chemotherapy medicines and newer targeted therapies such as the experimental PARP inhibitor in this study.

DNA carries genetic information in both healthy and cancer cells. The PARP (poly ADP-ribose polymerase) enzyme fixes DNA damage in cells, including DNA damage caused by chemotherapy medicines. Scientists developed PARP inhibitors based on the idea that a medicine that interferes with or inhibits the PARP enzyme might make it harder for cancer cells to fix damaged DNA, which could make chemotherapy more effective.

In this study, 123 women diagnosed with metastatic, triple-negative breast cancer already had received one or two previous treatments that had stopped working. Half the women got iniparib (given intravenously) and a combination of Gemzar (chemical name: gemcitabine) and carboplatin (brand name: Paraplatin), a common chemotherapy regimen. The other women got only Gemzar and carboplatin.

The researchers wanted to see how adding iniparib to the chemotherapy combination affected median survival time. Median survival time is the amount of time that half the women lived longer than and half the women lived shorter than. Median survival for women treated with iniparib and chemotherapy was 12.3 months compared to 7.7 months for women treated only with chemotherapy.

Adding iniparib to chemotherapy also improved progression-free survival. Progression-free survival is the amount of time the women lived without the cancer growing. Progression free survival was 5.9 months for women who got iniparib and chemotherapy compared to 3.6 months for women who got only chemotherapy.

About half of the women who got iniparib and chemotherapy had one or more signs that the treatment weakened the cancer. Only 32.5% of the women who got only chemotherapy had signs that the cancer was weakened. These statistics are called response rates.

Slightly more than half of the women who got iniparib and chemotherapy got some benefit from the treatment. Only 33.9% of the women who got only chemotherapy got some benefit. These statistics are called clinical benefit rates.

Most of the women had side effects that were bothersome but expected with these chemotherapy medicines, including hair loss, mouth sores, low blood cell counts, intestinal upset, and pain in the hands and feet. There were no differences in the type or severity of side effects in the two treatment groups:

  • 28% of women who got iniparib and chemotherapy had serious side effects
  • 29% of women who got only chemotherapy had serious side effects

Because the results of this study were promising, the researchers believe a larger study on using iniparib and chemotherapy to treat metastatic, triple-negative breast cancer should be done.

If you're being treated for metastatic, triple-negative breast cancer, you and your doctor may be considering a number of options, especially if the cancer has stopped responding to standard treatments. You may have other choices, including a PARP inhibitor such as iniparib, if you're willing to participate in a clinical trial. Ask your doctor if there are any clinical trials that might be a good fit for you and your unique situation. Visit the Breastcancer.org Clinical Trials pages for more information.

Stay tuned to Breastcancer.org Research News to learn about the latest information on new ways to more effectively treat breast cancer.

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