For the first time, a new immunotherapy showed positive results against triple-negative breast cancer, according to a study published Saturday in the New England Journal of Medicine, prompting some providers to express cautious optimism about the drug's ability to prolong survival.
What makes triple-negative breast cancer difficult to treat?
While researchers have begun integrating immunotherapies into treatment for various types of cancer, the drugs to date have not been effective in advanced triple-negative breast cancer, the AP reports.
According to the National Breast Cancer Foundation, about one in 10 of all breast cancers are "triple-negative"—that is, their growth isn't driven by estrogen, progesterone, or the specific gene targeted by the drug Herceptin. Triple-negative breast cancer primarily affects women in their 40s and 50s and is most common among Hispanic and African American women, as well as those with a BRCA1 gene mutation.
Triple-negative breast cancers don't respond to hormonal cancer treatments, and while they do respond to chemotherapy, researchers have found that cancer cells can develop resistance quickly and spread to other parts of the body.
Peter Schmid of Queen Mary University of London, who lead the latest study, said, "We have desperately been looking for better treatment options."
A new combination chemotherapy/immunotherapy approach shows promise
For the study, the researchers tested the effectiveness of a combination of chemotherapy and Tecentriq, Roche's version of the immunotherapy drug atezolizumab.
They divided 902 women with advanced triple-negative breast cancer into two treatment groups: a "combo" treatment group, as well as a control group that received standard chemotherapy as well as a placebo instead of the immunotherapy drug.
The combo group was administered Tecentriq biweekly to trigger the patients' immune systems to attack the cancer cells, as well as chemotherapy weekly to remove the "immune-protective cloak[s]" that shielded the cancer cells from being recognized and attacked by the patients' uninhibited immune system, according to Schmid.
The study found women in the combo group showed no progression of cancer for a 7.5 months—an average of two months longer than those in the chemotherapy treatment group.
The researchers found the treatment was even more effective among women with high levels of PD-L1, the protein that is deactivated by immunotherapy. According to the study, those women experienced an additional 2.5 months without their cancer progressing, living 10 months longer on average than women who received only chemotherapy.
But there were drawbacks. While almost all participants reported common chemotherapy side effects, such as low blood cell counts and nausea, women in the combo treatment group were twice as likely to experience "serious" side effects that caused them to halt treatment. Some patient deaths, AP reports, were attributed to the treatment itself.
Study results met with 'cautious excitement' from researchers
The study marks the first time immunotherapy has demonstrated effectiveness in treating such an aggressive breast cancer, Schmid said, calling the findings "a huge step forward for these breast cancer patients."
Larry Norton, director of the Evelyn H. Lauder Breast Center at the Memorial Sloan Kettering Cancer Center, who was not involved with the study, said, "This is a real advance that is going to allow us to help more people." Norton said he's "encouraged by the fact some patients [with high levels of PD-L1] are living without recurrence for an extended period of time."
Michael Hassett, a breast cancer specialist at the Dana-Farber Cancer Institute who was not involved with the study said he views the results with "cautious excitement," AP reports.
According to the AP, it remains to be seen whether the drug's "modest" benefits outweigh the side effects and treatment costs. The immunotherapy drug costs $12,500 a month, and the chemotherapy used in the study costs $3,000 per dose, not including physician fees.
Norton and other experts said they expect the findings will spur future research. Norton said he expects to see an "explosion of well-designed studies that will push the agenda forward" (Marchione, AP/Washington Post, 10/20; LaMotte, CNN, 10/21).
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