Amanda Pritchard suggested people may still be wary of burdening the health service as it continues to battle with the coronavirus pandemic.
But she said: “We are open and ready.”
And she added: “We know that thousands of people could be risking their lives by delaying medical attention for cancer symptoms.”
She spoke out ahead of a new campaign launching on Monday, which will seek to raise awareness of potential signs of abdominal area, urological and lung cancers.
The drive comes after research showed that 60 per cent of people in England are concerned about burdening the NHS, with 49 per cent saying they would delay seeking medical advice longer than they would have done before the pandemic.
Ms Pritchard said: “This campaign will remind people of the signs and symptoms to look out for and encourage them to get checked if something isn't quite right.
"Thanks to the hard work of NHS staff, we are back on track with cancer referrals, diagnosis and treatment so, whether you or a loved one has a routine appointment, or a potential cancer symptom, please don't delay and come forward to get yourself checked – we would rather see you sooner when any cancer would be easier to treat.”
She added it was “incredibly important” that people recognised common symptoms that can signal a cancer diagnosis.
They include ongoing abdominal discomfort, a persistent cough, diarrhoea that goes on for three weeks and returning chest infections.
Health Secretary Sajid Javid said: "NHS staff have pulled out all the stops to prioritise cancer care throughout the pandemic, with millions of diagnostic tests now being carried out a month. Thanks to their dedication, the NHS is open for us all and anyone who has concerns should come forward.
"If you suspect you might have symptoms of cancer, as highlighted by this important new campaign, don't hesitate to seek advice from your GP. The earlier we can spot cancer, the more lives we can save.”
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