By studying the genetic changes undergone by women who smoke, scientists in the UK have figured out how to detect several types of cancer around the body with almost perfect sensitivity, just by analysing a person's cheek cells.

The team wanted to investigate how epigenetic changes - changes to a person's DNA that switch genes on and off, caused by environmental factors such as exposure to cigarette smoke - can be identified early on in epithelial cancers, which encompass 80 to 90 percent of all known cancer types. They say that easily accessible cheek cells could make detecting the early warning signs of well-hidden cancers like ovary, breast and endometrial much simpler in the future.

"Our work shows that smoking has a major impact on the epigenome of normal cells that are directly exposed to the carcinogen," lead researcher Andrew Teschendorff, from the University College London Cancer Institute, said in a press release. "Of particular significance is that these epigenetic changes are also seen in both smoking-related and non-smoking related cancers, pointing towards a universal cancer program. This research gets us closer to understanding the very first steps in carcinogenesis and in future may provide us with much-needed tests for risk prediction and early detection."

Teschendorff and his team looked at the epigenetic changes that were occurring in cheek - or buccal - samples taken from 790 women all born in 1946. They found that those who smoked were more likely to display alterations in their epigenomes that were associated with several types of cancers, even those that are not usually linked to smoking. Through their analysis, they were able to come up with an epigenetic 'signature' for smoking.

"By looking for this signature, the researchers found they could differentiate between normal and cancerous tissue with near absolute certainty, including cancers in other parts of the body," Esha Dey reports at Live Science. "The signature could also be used to predict if a pre-cancerous lesion would progress to a full-blown invasive cancer, the researchers said."

Publishing in the journal JAMA Oncology, the team says that compared to blood samples taken from the female volunteers, the cheek cell samples showed a 40-fold increase in abnormal genetic activities, which makes them a better and more reliable indicator of these early warning signs. They report in the press release that their cheek cell test is able to discriminate between normal and cancerous tissue with almost 100 percent sensitivity and 100 percent specificity, regardless of the organ in which the cancer arose.

"These are significant results for our core interest, which is decoding women's cancers. We are a big step closer now to unravelling how environmental factors cause cancer," said Teschendorff. "These results pave the way for other studies in which easily accessible cells can be used as proxies to highlight epigenetic changes that may indicate a risk of developing cancer at a site where cells are inaccessible. This is incredibly exciting for women's cancers such as ovary, breast and endometrial cancer where predicting the cancer risk is a big challenge."

The good news for ex-smokers is that the team’s results showed that smoking-related damage experienced by the women in their analyses had been reversed in those who had quit smoking 10 years before the samples were collected, which means it’s never too late to lower your cancer risk if you’re thinking about quitting.