Complex sentence: After being in remission, the cancer returned around 2005 and spread to Nielsen's liver and bones, and in October 2008, Nielsen announced that her cancer had returned in the form of a brain tumour.
Split into simpler sentences: After being in remission, the cancer returned around 2005 and spread to Nielsen's liver and bones. In October 2008, Nielsen announced that her cancer had returned in the form of a brain tumour.