Researchers from Luton and Dunstable NHS Trust said poor GP access to tests and a lack of symptom awareness among patients meant many cases presented too late and often as emergencies.
They suggested NICE may need to lower the referral threshold so more patients have X-rays to catch cancers earlier.
The researchers presented a study of 144 lung cancer patients at the European Respiratory Society annual congress 2012 in Vienna last week. This showed cases presenting as inpatients had later-stage disease and poorer outcomes and survival chances than those referred by their GP as outpatients.
Presenting the findings, co-author Dr Laura Succony said: 'While we acknowledge there is a possibility that patients presenting to A&E have more rapidly progressing disease, we feel that it is much more likely explained by delays in the system, with patients being missed earlier on in the disease pathway leading to later presentation in the disease course.'
Dr Succony said primary care may not offer enough chest X-rays because the threshold – to urgently refer patients who have symptoms for at least three weeks – is set too high.
'There is limited access to diagnostics in primary care,’ said Dr Succony. ‘We have NICE guidelines, but are they perhaps too stringent? Should we be X-raying more patients?'
But she added: 'I appreciate it is very difficult for GPs, who are seeing a huge amount of patients with symptoms.’
The DH has pledged to boost GP access to diagnostics as part of its cancer strategy. But Yorkshire GP Dr Nick Summerton, a DH cancer adviser, said the NHS should offer more low-dose CT scans for suspected lung cancer despite the extra cost instead of cheaper X-rays.
'It's not a particularly good way of diagnosing early-stage cancer,' he said. 'There are problems with validity and reliability. Some GPs are reassured by a normal chest X-ray, but this can delay diagnosis. It's a cost issue at the end of the day.'
US research has suggested low-dose CT could be a cost-effective way to offer targeted screening for lung cancer.