An immunotherapy drug has shown promise for the first time in a form of aggressive breast cancer.
Researchers found that combining the immune-boosting drug atezolizumab (Tecentriq) with routine chemotherapy extended the lives of some women with triple negative breast cancer by 10 months.
But the treatment didn’t work for everyone. The benefits were most clearly seen for women whose tumour samples contained high levels of a molecule, called PD-L1.
The immunotherapy drug blocks this molecule so that immune cells can attack the cancer.
Professor Charlie Swanton, Cancer Research UK’s chief clinician, said that the results suggest immunotherapy could be a potential new option for women with triple negative breast cancer.
“For some women on the trial, whose tumours contained high levels of a particular molecule, survival increased by nearly a year which is very hopeful indeed,” he said.
The results were published in the New England Journal of Medicine and presented at the European Society of Medical Oncology congress in Munich, Germany.
What did the trial show?
The trial involved 902 women with untreated, triple negative breast cancer that had spread to other parts of the body.
Patients received either atezolizumab plus the chemotherapy drug nab-paclitaxel, or chemotherapy plus a dummy drug.
Atezolizumab didn’t significantly improve patient survival overall, but there were encouraging signs in patients whose tumour samples carried high levels of PD-L1, as measured by lab tests.
Women with high levels of this marker who had immunotherapy lived around 25 months on average, compared to 15 months for women who didn’t.
Severe side effects were more common in women taking the combined immunotherapy and chemotherapy, with twice as many women stopping treatment due to side effects than those taking chemotherapy alone.
Around half the women on the trial were deemed to have high levels of the PD-L1 molecule in their tumour samples.
Aggressive form of cancer
Triple negative breast cancer is an aggressive form of cancer that often affects younger women, with many patients diagnosed in their 40s and 50s.
It is not a common type of breast cancer, but it is particularly hard to treat.
The trial combined patients’ regular weekly chemotherapy with fortnightly immunotherapy, which boosts the immune system’s ability to see and kill cancer cells.
Swanton said that while the treatment didn’t represent a cure, the results could offer patients the potential of more time with their friends and families in the future.
Atezolizumab is already available to treat some advanced lung and bladder cancers in the UK. It has not been approved as a treatment for breast cancer and will need to be reviewed separately before it can be used to treat women with this type of breast cancer.
Schmid, et al. (2018) Atezolizumab and Nab-Paclitaxel in Advanced Triple-Negative Breast Cancer. NEJM. DOI: 10.1056/NEJMoa1809615