One in three people with cancer feels lonely and isolated, with most putting "a brave face" on their situation, a poll has found.
The survey of more than 1,000 people for Macmillan Cancer Support found one in three people affected by cancer recently felt lonely or isolated.
Of these, 88% did not want to burden other people with their feelings.
One in seven said they were embarrassed to talk about loneliness, while one in 12 worried they would be viewed differently.
Around one in 10 said they did not know where to turn for support.
Macmillan has re-launched its online community forums to help people share experiences about living with cancer.
Jacqui Graves, head of health and social care at Macmillan Cancer Support, said: "We know that if you're living with cancer and feeling lonely, it can have a devastating impact, with many people forced to skip meals or attend vital appointments alone.
"At worst this can result in patients refusing treatment altogether. That's why it's so important that people reach out and get support. There is an army of people within thecancer community who can help, no one has to face cancer alone.
"If I've got one piece of advice, it's don't suffer in silence."
Dave Rundle, 65, from Devon, was diagnosed with prostate cancer in 2014.
He said: "I was in pieces when I got my diagnosis. The only experience of cancer before this was watching my first wife die from it.
"My family and friends were there, but you can't imagine how lonely it is to struggle with everyday tasks you take for granted.
'I turned not only to Macmillan's support line but to the online community as I knew it'd be the place where I'd find others going through exactly the same problems and issues.
"There was always somebody there to listen."