“…Among the selected trials, nine were conducted in China (11,13,15,16,(25)(26)(27)(28)(29), four in the United States (30)(31)(32)(33), three in the United Kingdom (34-36), two in Norway (37,38), two in Italy (39,40), and one each in Poland (41), Australia (42), Russia (43), Germany (44), Belgium (45), Iran (46), and the former Soviet Union (47). Of these, 11 trials investigated the effects of progestin-based combination therapy versus progestin alone or other treatments (11,13,15,16,25,27,28,31,32,42,43), another 11 trials explored the efficacy of progestin alone versus non-progestin treatments (26, 30, 33-35, 37, 40, 41, 44, 45, 47), and 5 trials compared the efficacy of different progestin treatments used alone (29,36,38,39,46). Most studies incorporated two or more outcome indicators, while a few focused solely on a single survival metric, Overall Survival (OS) (33,34,37,41,43,…”