Complex sentence: He claims to be able to reverse the cancer process in metastatic cancer by a success rate of complete remission in about a third of cases, and claims that almost everybody else live significantly longer with a much better quality of life.
Split into simpler sentences: He claims to be able to reverse the cancer process in metastatic cancer by a success rate of complete remission in about a third of cases. Almost everybody else live significantly longer with a much better quality of life.