https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3059315/
没时间就读2.1即可。
如果这也太多，就读下面一段。
"Despite the limitations, single-arm trials may be the only (or one of few) options for trials evaluating therapies for which placebos are not ethical and options for controlled trials are limited. Single-arm trials have been commonly implemented in oncology."
