A large Phase III trial, the Impassion130 trial, has produced results supporting the use of chemotherapy plus immunotherapy as first-line treatment in certain patients with triple-negative breast cancer. The trial evaluated the combination of nab-paclitaxel, which is a chemotherapy drug, and atezolizumab, which is a checkpoint inhibitor. Together, the chemotherapeutic and the checkpoint inhibitor performed better than the chemotherapeutic alone. They increased both progression-free survival and overall survival.
Detailed results were presented at the ESMO 2018 Congress, currently taking place in Munich, and in an article (“Atezolizumab and Nab-Paclitaxel in Advanced Triple-Negative Breast Cancer”) that appeared October 20 in the New England Journal of Medicine (NEJM). According to the article’s senior author, Leisha Emens, M.D., Ph.D., a researcher at the University of Pittsburgh School of Medicine, the significance of the results are as follows: a new standard of care in patients with triple-negative breast cancer who are positive for programmed death ligand 1 (PD-L1).
In triple-negative breast cancer patients, the PD-L1 protein is found mostly on immune cells that infiltrate the tumor. Blocking PD-L1 with the checkpoint inhibitor atezolizumab reinvigorates these immune cells, allowing them to attack the tumor.
“While chemotherapy is the current standard of treatment for triple-negative breast cancer, there is an urgent need for newer, more effective therapies,” says Dr. Emens. “The results of this trial showed that adding the immunotherapy drug atezolizumab to chemotherapy was well-tolerated and resulted in a clear increase in clinical benefit for some patients with triple-negative breast cancer.”
According to the article, the trial enrolled 902 patients with either metastatic or locally advanced triple-negative breast cancer that could not be surgically removed. Patients were enrolled at 246 sites in 41 countries across the world and were randomly assigned to receive either atezolizumab or a placebo, along with the chemotherapy drug nab-paclitaxel.
In the overall patient population, the researchers found a statistically significant increase in progression-free survival in patients treated with both nab-paclitaxel and atezolizumab—7.2 months when compared to 5.5 months in patients who received chemotherapy alone. In the group of patients who expressed the PD-L1 protein on tumor-infiltrating immune cells, the combination treatment had a more significant impact on progression-free survival—7.5 months versus 5 months.
Overall survival was 21.3 months in the combination treatment group as compared to 17.6 months with chemotherapy alone, though this did not reach statistical significance in this first analysis. In the group of patients who expressed PD-L1 on their tumors, the difference in survival was greater, with overall survival of 25 months, in contrast to 15.5 months in patients treated with nab-paclitaxel alone.
“A benefit with atezolizumab–nab-paclitaxel in patients with PD-L1–positive tumors that was shown in our trial provides evidence of the efficacy of immunotherapy in at least a subset of patients,” wrote the authors of the NEJM article. “It is important for patients’ PD-L1 expression status on tumor-infiltrating immune cells to be taken into consideration to inform treatment choices for patients with metastatic triple-negative breast cancer.
“The trial showed activity for the combination of atezolizumab and nab-paclitaxel in patients with metastatic triple-negative breast cancer; it remains to be determined whether these findings extend to other chemoimmunotherapy combinations.”
The adverse events observed were similar to the known adverse event profile of the two drugs. Patients who received both immunotherapy and nab-paclitaxel experienced a higher frequency of adverse events that were potentially immune-related, than those who received chemotherapy alone, at 7.5% versus 4.3%, respectively.