Article continues below advertisementOK! can reveal how David Bowie kept his 18-month battle with liver cancer hidden as he recorded his final album, Blackstar.The iconic singer-songwriter, who died at age 69 in January 2016, is remembered in the upcoming documentary Bowie: The Final Act - which is set to be released just ahead of the 10th anniversary of his passing - and we can report it contains moving footage of his longtime producer Tony Visconti recalling the moment he realized the horrific scale of Bowie's illness.