Cancer referrals vary widely between patients, a study has found.
While the majority of patients (77%) who visited their doctor with suspicious symptoms were referred to hospital after just one or two consultations, almost a quarter had to meet their GP a number of times before a specialist referral was made.
The Cambridge-led study also revealed that patients who were female, young, or elderly and from an ethnic minority - as well as those with less common forms of the disease - had the highest number of GP appointments before being referred to hospital.
The earlier cancer is detected and treated the higher the chances of a full recovery, which raises concerns over the impact of these delays.
Lead investigator Dr Georgios Lyratzopoulos, clinical senior research associate at the University of Cambridge, said, as reported by the Press Association: "These findings highlight limitations in current scientific knowledge about these cancers.
"Medical research in recent decades has prioritised improving cancer treatments, but knowledge about the 'symptom signature' of common cancers and practical solutions on how best to diagnose them is still emerging.
"Hopefully, our study will stimulate investment into research, focusing on patients with cancers and characteristics where the potential to improve the experience of diagnosis of cancer is greatest."
Jessica Harris, health information manager at Cancer Research UK, warns of the challenges facing family doctors in diagnosing cancer.
She said in a statement: "This study highlights some of the difficulties in diagnosing cancer in primary care. A GP will see only around eight cases of cancer a year, on average, among hundreds of people with symptoms that might indicate cancer, so making appropriate referral decisions can be challenging, especially for rarer cancers or those with symptoms that are vague or common to other diseases."
Harris also stresses the importance of patients being vigilant with their own symptoms and taking action where necessary.
She added: "As part of the National Awareness and Early Diagnosis Initiative, Cancer Research UK is working hard to achieve earlier diagnosis of cancer, and funding research into how referral decisions can be made more easily in primary care. But it's also very important for people to get to know their body and what is normal for them, and go to see the GP if they notice any persistent or unusual change. And do go back if your symptom has changed, not gone away or got worse."
The study looked at data from 41,000 adults with 24 different types of cancer, from the 2010 National Cancer Patient Experience Survey.
They found more common types of cancer, such as breast, melanoma, testicular and endometrial cancers were more likely to be referred to a specialist after just one or two consultations.
In comparison, patients with multiple myeloma, pancreatic, stomach, ovarian, lung and colon cancers - which are notoriously more difficult to spot - were more likely to require three or more GP consultations before they were referred to a hospital specialist.
A Department of Health spokesman said: "Around a third of people diagnosed with cancer in England die within a year. We have committed £450 million to help diagnose cancer earlier, and achieve our goal of saving 5,000 extra lives every year. This money will give GPs direct access to tests to allow quicker diagnosis.
"This extra investment will also fund awareness campaigns of signs and symptoms for GPs and the public, as well as the extra costs for secondary care as more people are referred for specialist treatment."