Shortly before O'Sullivan was to begin rehearsals in Wales, she was diagnosed with cancer. The stage 2 leg tumour was discovered by her
beautician during a waxing session. O'Sullivan had previously dismissed the lump as
cellulite. The diagnosis did not affect her performances, as she received initial radiotherapy treatment in Ireland and then in Wales, continuing to work throughout, performing 20 times in 14 weeks. O'Sullivan had
nodules removed from her
vocal cords at the private
Blackheath Hospital, London. After the operation, she recuperated at
Glenstal Abbey, where she was completely silent for one week. In 2018, O'Sullivan was diagnosed with early-onset
dementia which led to her retirement from professional singing. Celebratory concerts were organised in her honour in Cork and Dublin. On 26 January 2021, it was announced that Cara O'Sullivan had died. Her death was marked by an outpouring of tributes to her talent and her outstanding contribution to music in Ireland and internationally, ==Legacy==