Sifting through a patient's prescriptions could help lead to earlier identification of those with cancer, experts say.
It is hoped that looking for patterns in prescriptions, or other data, may lead GPs to diagnose the disease earlier.
A new study has been launched to look at the links between medication use and subsequent diagnosis of cancer.
Small studies from Denmark have suggested that many lung cancer patients have a history of being given prescriptions for antibiotics.
The new study is being led by Health Data Insight, which has created an anonymous dataset with Public Health England and the NHS Business Services Authority.
This dataset will look at around 80 million medications being prescribed each month across England.
The researchers will then link this information to data in the National Cancer Registration and Analysis Service to look for trends in medications given to patients before they were diagnosed with cancer.
Only around half of those with the most common cancers have "red-flag" symptoms, such as blood in the stools of bowel cancer patients or lumps among breast cancer patients.
Cancers with poor survival rates such as pancreatic, stomach, ovarian and brain cancer, can also often have very few symptoms.
In April, research published in the British Journal of General Practice found that thousands of people diagnosed with cancer in A&E every year have visited their GP three times or more with symptoms.
The study showed that 71% of all patients diagnosed as an emergency had seen their GP at least once with symptoms that turned out to be cancer. The remainder had never visited their GP.
Of the group that did see their GP with symptoms, 41% had sought help three or more times, while 59% had seen their GP once or twice.
Some of these had difficult-to-spot cancers, such as lung cancer or multiple myeloma, and tended to be younger or female.
But the group also included people with common cancers such as breast cancer (31% of breast cancer patients had visited their GP three or more times), bowel cancer (41% had visited three or more times) and prostate cancer (37% had visited three or more times).
Dr Jem Rashbass, medical director at Health Data Insight, said of the new study: "We want to develop a tool that helps GPs diagnose cancer earlier in the hope of saving more lives.
"It can be very difficult for GPs to know which patients to refer for further tests.
"Large studies like this are only possible because anonymous data on large numbers of cancer patients is available for research through the NHS.
"Our idea is to use this unparalleled information on prescription data and other information to better identify patients for referrals or follow-up."
Dr Iain Foulkes, director of research and innovation at Cancer Research UK, which provided funding for the study, said: "Cancer survival in the UK lags behind other countries in Europe, in part because people are diagnosed later when the disease is more advanced and harder to treat.
"Dr Jem Rashbass is collecting a wealth of data which he can then mine for new ways to diagnose cancer earlier.
"This is a potentially powerful study that could transform the way cancer is detected and is made possible because of the unique strengths of the UK health system."
Professor Helen Stokes-Lampard, chairwoman of the Royal College of GPs, welcomed the study.
She said: "Some of the most common and most dangerous cancers don't have 'red flag' symptoms and can have very similar symptoms to more common, non life-threatening conditions.
"This makes diagnosis in general practice incredibly difficult, especially within the constraints of the standard 10-minute consultation, and currently we have one of the lowest access rates to diagnostic tests in Europe.
"Nevertheless, GPs are already doing a good job of appropriately referring our patients that we suspect of having cancer."
She said the proportion of cancers diagnosed as an emergency had dropped from 25% to 20%, and a higher proportion of patients were diagnosed at an earlier stage.