"Of course I've been affected by my brother's death," Smith told the Radio Times. "It makes me value life, cherish my loved ones and be grateful for every day I have with them."
The feature-length BBC drama is based on the life of journalist Lisa Lynch who was diagnosed with breast cancer at 28 and wrote a blog about her journey, which was eventually turned into bestselling book The C Word. Lisa underwent a mastectomy, chemotherapy and radiotherapy and was given the all-clear from a 2009 mammogram. But the cancer returned two years later and it was terminal. In October 2012 Lisa was told the cancer had spread to her brain and that she only had months to live. She died five months later at the age of 33.
The television adaptation of Lisa's book was already underway before she died and she contacted Sheridan herself to ask her to take on the lead role.
"Lisa contacted me via Twitter," Sheridan told the Daily Mail. "She said I was the only person she wanted to play her in a TV version of her book and would I do it? So I read it and my first thought was, 'You must be joking!' I was worried about upsetting members of her family, I thought she was everything I'm not: incredible, funny, amazing, strong. I'm a wuss and she's not. I wasn't sure I could do her justice."
Sheridan hopes the TV drama will encourage people to be more willing to discuss cancer and death.
"Lisa's blog was her way of dealing with it, so that when she was around her family they didn't have to constantly talk about 'it' but at the same time, it raises awareness of breast cancer in a really positive way," she said. "I'm hoping the film will raise an even wider awareness, because if people haven't been affected by cancer, they might not pick the book up, but if it's on television there's a chance they'll tune in and get the message."
Sheridan told the BBC: "My favourite line [in the drama] is when [Lisa] goes: 'I'm British. We just don't talk about things like that.' And it gets me every time, because we don't. And it's cancer. It touches one in three and every single one of us will, if we haven't experienced it, know a friend who has. We should talk about it. It's not a taboo subject. It should be spoken about."
Video credit: BBC/YouTube
The C Word is on BBC1 on Sunday, May 3 at 8:30 p.m.
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