Lorna Luft, the daughter of US actress Judy Garland, has been diagnosed with a brain tumour after collapsing following a performance in London.
The singer, 65, was “forgetting lyrics and monologue” before she collapsed back stage at the Pizza Express Jazz Club on Friday night.
She was rushed to hospital by her husband, Colin Freeman, who had been concerned for Luft during her performance, spokeswoman Victoria Varela said.
Luft, an Emmy-winning TV producer and Broadway star, is currently in remission from breast cancer which she has been battling for more than six years.
Ms Varela said: “Luft was rushed to hospital by Colin Freeman, her husband, who was also concerned that she was forgetting lyrics and monologue.
“Following admission to hospital, Luft has been initially diagnosed with a brain tumour.
“Further information will be available following additional medical tests and examinations.”
Luft’s performance at the Jazz Club on Friday was the second of four sold-out shows at the venue.
Her father is producer Sidney Luft and she is the half-sister of actress and singer Liza Minnelli.