Effect and Safety of Anti-PD-1/PD-L1 Monotherapy for Metastatic Breast Cancer: A meta-analysis

Abstract

Background. Given that no approved targeted agents for metastatic triple-negative breast cancer (mTNBC) and no opportunity of surgery for metastatic breast cancer (MBC), new treatment options are urgently to be discovered. The anti-PD-1/PD-L1 immunotherapy may be effective, and what we should be aware of is the response rate and adverse events. Methods. The PUBMED, EMBASE, Cochrane and www.clinicaltrials.gov databases were searched to find potential studies using the following strategies: anti-PD-1/PD-L1; metastatic; breast cancer. R© package Meta was used to pool incidence. Results. Six studies including 586 advanced breast cancer patients treated with anti-PD-1/PD-L1 agents were included in this meta-analysis. The anti-PD-1/PD-L1 agents include pembrolizumab, atezolizumab and avelumab. Among these patients, CR was 1.26%, PR was 7.65%, ORR was 9.85% and DCR was 18.33%. We also found that the response rate was closely associated with the expression of PD-L1 biomarker (PD-L1+ vs PD-L1-): the CR was 2.71% vs 0.00%; the PR was 9.93% vs 2.69%; the ORR was 10.62% vs 3.07%; the DCR was 17.95% vs 4.71%. 1-year overall survival rate and 6-months progression-free survival rate were 43.34% and 17.24%. Respectively, the overall incidence of AEs was 64.18% in any grade and 12.94% in severe grade. The incidence of irAEs was 14.75%. Besides, the incidence of discontinue and death due to treatment-related AEs was about 3.06% and 0.31% respectively. When the detailed AEs were analyzed, most treatment-related AEs of any grade were arthraigia, asthenia, decreased appetite; most common treatment-related AEs of severe grade were anemia, autoimmune hepatitis, diarrhea; the most common irAEs were hypothyroidism , followed by hyperthyroidism, pneumonitis and infusion-related reaction. Conclusions. Anti-PD-1/PD-L1 monotherapy showed a manageable safety profile and had a durable anti-tumor clinical activity in a subset of patients with mTNBC or MBC. PD-L1 expression may be correlated to a higher probability of clinical response.