By Joyce Bichler, Deputy Director
Recent news that some patients with metastatic triple negative breast cancer live longer with immunotherapy plus chemotherapy was cheered by many in the breast cancer community and sparked renewed excitement about the potential of immunotherapy. At Breast Cancer Action, we celebrate anytime a new breast cancer treatment helps patients live longer. And all the more when that treatment helps patients with a particularly poor prognosis.
Despite much hype over the years, and significant benefit of immunotherapy in melanoma and lung cancer, this is the first time researchers have found a survival benefit of immunotherapy in breast cancer. And yet there are important unanswered questions about the findings.
Let there be no question: we urgently need better treatments for triple negative breast cancer, which is an aggressive cancer subtype. In fact, in some ways you could say triple negative breast cancer is defined by the lack of targeted treatment options. Unlike some other breast cancer subtypes, triple negative breast cancer is not responsive to hormone therapy or HER-2 therapies, which can be used in addition to or instead of chemotherapy. Around 15 percent of all breast cancers are triple negative, and African American women and young women are more likely to be diagnosed with triple negative breast cancer. Without targeted therapies, the main treatment for triple negative breast cancer is chemotherapy and most patients with metastatic disease develop resistance to chemotherapy within a few months. When triple negative breast cancer spreads to other parts of the body, or metastasizes, average survival is just a year to a year and a half.
The new study trial reported at the ESMO 2018 Congress in Munich has found that the combination of an immune therapy and chemotherapy can help some patients with triple negative breast cancer live longer.
More than 900 patients who were newly diagnosed with metastatic triple negative breast cancer were enrolled in the IMpassion130 trial, which provided all patients with first-line treatment with the chemotherapy nab-paclitaxel (produced by Celgene under the brand name Abraxane). Half of the patients were randomly allocated to receive this standard chemotherapy plus placebo, while the other half received the chemotherapy with an immune therapy atezolizumab (produced by Genentech under the brand name Tecentriq), which selectively targets the protein PD-L1.
The initial analysis found a small benefit, around 3 months, in progression free survival, or time that the cancer does not grow. The hope is that this points to benefit in overall survival, which is after all the only way to know if patients live longer as a result of treatment. The overall survival data was not statistically significant, but the researchers found a benefit to overall survival for all patients in the study – 21.3 months with the combination versus 17.6 months with chemotherapy alone. A larger survival benefit—though also statistically insignificant—was found from an interim subgroup analysis which showed 10 months survival improvement in patients with PD-L1 positive tumors. The median overall survival for patients in this subgroup was 25 months with the combination compared to 15 ½ months with standard chemotherapy alone. Forty-one percent of patients in the study had positive PD-L1 expression.
The addition of the immunotherapy comes with somewhat worse side effects including grade 3-4 peripheral neuropathy, which was more common in the atezolizumab group (6 percent versus 3 percent of patients), and the likelihood of a decreased neutrophil count (5 percent versus 3 percent).
We look forward to final analysis and the results of longer follow up with the patients in this study. And we recognize questions have been raised about the best chemotherapy to be paired with atezolizumab. We also need to answer some of the concerns about PD-L1 testing and to better know to whom this treatment needs to be targeted for best results. And most of all, we need to know that as treatments are developed, the women who need them will have access to them. Atezolizumab costs over $100,000 a year for treatment—we cannot have women being forced to choose between a chance for longer life or bankruptcy.
While this preliminary analysis suggests this treatment may be very promising for some women with triple negative breast cancer—specifically those with PD-L1 expression—until, and unless, final analysis shows statistically significant overall survival benefit, this treatment remains experimental. We hope to celebrate a new treatment option for women who until now did not have any good options. And we will work to make sure that everyone who needs life-saving healthcare and treatment can access and afford them.