Chemoimmunotherapy in the Treatment of Breast Cancer − Final Results of the IMpassion130 Study
According to international recommendations, treatment with the immune checkpoint inhibitor atezolizumab in combination with the cytostatic nab-paclitaxel is used for patients with locally advanced or metastatic breast cancer where PD-L1 protein expression is detected on the surface of tumor-infiltrating immune cells (IC). The final results regarding overall survival and long-term safety of this treatment in patients who participated in the registration study IMpassion130 were presented at this year's European Society for Medical Oncology (ESMO) congress, which was held virtually due to circumstances.
Study Methodology
Patients with previously untreated metastatic triple-negative breast cancer were randomized in a 1:1 ratio to receive nab-paclitaxel in combination with atezolizumab or placebo. The treatment continued until disease progression or unacceptable toxicity occurred. Patients were stratified based on prior (neo)adjuvant taxane therapy, the presence of liver metastases at study entry, and PD-L1 expression (positive vs. negative). The primary endpoints of the study were progression-free survival (PFS) and overall survival (OS).
Results
Therapy Effectiveness
185 patients treated with atezolizumab and 184 in the placebo group had positive PD-L1 expression, with a median OS for this group of 25.4 months (95% confidence interval [CI] 19.6–30.7) in the atezolizumab arm and 17.9 months (95% CI 13.6–20.3) in the placebo arm.
As of April 14, 2020, 666 of 902 participants (73.8%) had died, with a median follow-up time of 18.8 months. At the end of the follow-up period, 6% of patients in the atezolizumab arm and 2% in the placebo arm remained on any treatment. The median OS for the entire intention-to-treat (ITT) population was 21.0 months (95% CI 19.0–23.4) in the atezolizumab arm and 18.7 months (95% CI 16.9–20.8) in the placebo arm.
Safety Profile
The safety profile analysis was possible for 460 patients in the atezolizumab arm and 430 in the placebo arm. Grade 3–4 adverse events occurred in 51% of patients in the atezolizumab-treated group and 43% in the placebo arm. Approximately 1% of patients in each arm experienced a grade 5 adverse event; however, no new grade 5 events or new safety trends were observed since the last analysis.
Treatment was discontinued due to adverse events in 19% of patients in the atezolizumab arm and 8% in the placebo arm. The most common reason was neuropathy, and treatment discontinuation was more related to nab-paclitaxel administration.
Conclusion
It has been confirmed that the combination of atezolizumab with nab-paclitaxel is safe and well-tolerated. The results of this final IMpassion130 analysis are consistent with previous analyses. Although the difference in overall survival for the ITT population between the study arms was not statistically significant, the OS difference for patients with positive PD-L1 expression was clinically significant.
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Sources:
1. Emens L. A., Adams S., Barrios C. H. et al. IMpassion130: final OS analysis from the pivotal phase III study of atezolizumab + nab-paclitaxel vs placebo + nab-paclitaxel in previously untreated locally advanced or metastatic triple-negative breast cancer. Ann Oncol 2020; 31 (suppl_4): S1142–S1215, doi: 10.1016/annonc/annonc325.
2. Schmid P., Adams S., Rugo H. S. et al. Atezolizumab and nab-paclitaxel in advanced triple-negative breast cancer. N Engl J Med 2018; 379 (22): 2108–2121, doi: 10.1056/NEJMoa1809615.
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