Patients say they would delay seeing a GP
Nearly 40% of Britons would delay going to a GP with cancer symptoms because they would be worried about wasting the doctor's time, a survey suggests.
The Cancer Research UK poll of 2,200 people also found 37% would be put off because they were frightened, while one in five said they would be embarrassed.
The charity said such attitudes could be "dangerous" as late diagnosis lowered the chances of survival.
GPs said people needed more convincing that cancer was not a "death sentence".
Cancer survival rates have been rising over recent decades.
However, the UK still lags behind many European countries, partly because of late diagnosis.
The government has responded to this by introducing some of the NHS's shortest waiting times for cancer care.
But the poll, which will be published at the National Cancer Research Institute conference in Birmingham later, suggests even guaranteeing quick treatment may not be the solution.
Professor Jane Wardle, from Cancer Research UK, said: "It's typically British to think 'I mustn't bother the doctor'.
"But when this etiquette stops us talking to the GP about potentially serious symptoms, it can be dangerous.
"A lot of work needs to be done to help people feel like they can go to their doctor as soon as they find something that could be a symptom of cancer."
Interestingly, among the survey sample, women were most likely to put off going to see a GP - it is commonly assumed men are worse.
In total, 41% admitted they would delay a visit because they would be worried about wasting their doctor's time, compared with 36% of men.
And 40% of women said fear would stop them, compared with 34% of men.
Meanwhile, one in five of all respondents said they would be too embarrassed to seek help and more than one in four said they would be too busy.
However, awareness of cancer symptoms was much more encouraging.
Well over 90% recognised that swelling or a lump could be a sign of the disease and 60% said they knew that a less obvious problem, such as a sore not healing, was also a sign.
Professor Steve Field, president of the Royal College of GPs, agreed the findings were concerning.
He added: "We must do more to convince people that cancer is not a death sentence."
A Department of Health spokesman said: "It is vital that anyone with cancer symptoms sees their GP urgently to get checked out. We know that, generally, the earlier a cancer is diagnosed, the greater the chance that it can be treated successfully."