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Pharmacol."],"abstract":"<jats:p><jats:bold>Background:<\/jats:bold> Success has been reported in PD-1\/PD-L1 blockade <jats:italic>via<\/jats:italic> pembrolizumab, atezolizumab, or avelumab monotherapy in manifold malignancies including metastatic breast cancer. Due to lack of large-scale study, here we present interim analyses to evaluate the safety and efficacy of these promising strategies in patients with advanced breast cancer.<\/jats:p><jats:p><jats:bold>Methods:<\/jats:bold> Six studies including 586 advanced breast cancer patients treated with anti-PD-1\/PD-L1 monotherapy agents before July 1, 2020, were included. The anti-PD-1\/PD-L1 agents include pembrolizumab, atezolizumab, land avelumab. Statistics was analyzed by R software and IBM SPSS Statistics 22.<\/jats:p><jats:p><jats:bold>Results:<\/jats:bold> Global analysis showed that for this monotherapy, the complete response was 1.26%, partial response was 7.65%, objective response rate (ORR) was 9.85%, and disease control rate (DCR) was 18.33%. 1-year overall survival rate and 6-month progression-free survival rate were 43.34 and 17.24%. Overall incidence of adverse events (AEs) was 64.18% in any grade and 12.94% in severe grade, while the incidence of immune-related AEs (irAEs) was approximately 14.75%: the most common treatment-related AEs of any grade that occurred in at least 5% of patients were arthralgia and asthenia; the most common severe treatment-related AEs occurred in at least 1% of patients were anemia and autoimmune hepatitis; the most common irAEs were hypothyroidism. Besides, the incidence of discontinue and death due to treatment-related AEs was about 3.06 and 0.31%, respectively. Additionally, by comparing efficacy indicators between PD-L1\u2013positive and PD-L1\u2013negative groups, an implicated correspondence between efficacy and the expression of PD-L1 biomarker was found: the PR was 9.93 vs 2.69%; the ORR was 10.62 vs. 3.07%; the DCR was 17.95 vs. 4.71%.<\/jats:p><jats:p><jats:bold>Conclusion:<\/jats:bold> Anti\u2013PD-1\/PD-L1 monotherapy showed a manageable safety profile and had a promising and durable anti-tumor efficacy in metastatic breast cancer patients. Higher PD-L1 expression may be closely correlated to a better clinical efficacy.<\/jats:p>","DOI":"10.3389\/fphar.2021.653521","type":"journal-article","created":{"date-parts":[[2021,6,29]],"date-time":"2021-06-29T05:49:50Z","timestamp":1624945790000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":21,"title":["Efficacy and Safety of Anti-PD-1\/ PD-L1 Monotherapy for Metastatic Breast Cancer: Clinical Evidence"],"prefix":"10.3389","volume":"12","author":[{"given":"Yihang","family":"Qi","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lin","family":"Zhang","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zhongzhao","family":"Wang","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiangyi","family":"Kong","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jie","family":"Zhai","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yi","family":"Fang","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jing","family":"Wang","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2021,6,29]]},"reference":[{"key":"B1","unstructured":"Breast Cancer Survival Rates2017"},{"key":"B2","doi-asserted-by":"publisher","first-page":"397","DOI":"10.1093\/annonc\/mdy517","article-title":"Pembrolizumab Monotherapy for Previously Treated Metastatic Triple-Negative Breast Cancer: Cohort A of the Phase II KEYNOTE-086 Study","volume":"30","author":"Adams","year":"2019","journal-title":"Clin. 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