Can serous endometrial cancer recur after treatment?

My sister 62 diagnosed with serous endometrial cancer stage 4 with peritoneal and pelvic lymph nodes mets diagnosed June 2025 and started on carboplatin + taxol+ durvalumab from June 2025 until January 2026 cancer progressed and received 2 cycles in f doxrobixin but she couldn’t tolerate then on MArch 2026 started on pembrolizumab and lenvatinib it works until July 1st started to have severe hypothyroidism and fatigue , her doctor asked us to stop for 2 weeks then she started to develop ascites she is admitted 2 times for drainage and currently she is hospitalized for same reason CT showed stable endometrial , ovarian , pelvic lymph nodes and peritoneal Mets but there is omental cacking and Mets her oncologist resumed lenvatinib at 10 mg and pembrolizumab and he said it may not work but he will repeat scan after 6-8 weeks Here CA125 was 900 when she was off medication and now it’s 600 , she is feeling much better after ascites drainage however she is so afraid from the recurrence and her oncologist 3rd line will be single chemotherapy and it’s effectiveness will be 20-30% , any one have same problem what other lines , any benefits from clinical trial knowing how aggressive is serous endometrial cancer we are so worried form this situation