In the four-part show, archival footage and personal videos and photos are intertwined with present-day interviews and scenes of the group embarking on their 2022 tour
Walters, who rose to prominence for her portrayal of a mature student learning beside an alcoholic professor played by Michael Caine in the 1983 film Educating Rita, said she was now "really well".
She described the shock at being told by a doctor that she had cancer.
"He said: 'Well I,'m worried it is cancer,'" Walters, 69, told the BBC. "The impact: "Shock. First of all, shock."
"I've just had a scan, and I know that [I'm] clear," she said.
The illness meant she had to be cut from certain scenes in the soon-to-be-released film The Secret Garden, in which she stars alongside Colin Firth, the BBC said.