Men drink and smoke more than women — but that is not the reason they have a higher cancer risk.
A major study suggests biological differences are the real reason behind the disparity between the sexes.
Understanding these differences could help to improve prevention and treatment, researchers say.
The study looked at 300,000 middle-aged and older Americans who did not have cancer over 15 years.
Men were more than twice as likely to develop the disease compared to women — even when lifestyle factors were ruled out.
‘This suggests that there are intrinsic biological differences between men and women that affect susceptibility to cancer,’ said lead researcher Dr Sarah Jackson, an epidemiologist at the National Cancer Institute.
Researchers suggested differences in genes, hormones and the immune system all play a role.
Scientists have thought men’s propensity to enjoy a few more drinks and take more smoke breaks than women was why they had higher rates of cancer in general. But now a major study of 300,000 Americans by the National Cancer Institute suggests biology makes men more vulnerable to cancer, not bad health habits
FACTORS THAT INCREASE CANCER RISK
For most people, increasing age is the biggest risk factor for developing cancer. In general, people over 65 have the greatest risk of developing cancer. People under 50 have a much lower risk.
Cancer is very common and most people have relatives who have had cancer. People often worry that a history of cancer in their family greatly increases their risk of developing it. But fewer than 1 in 10 cancers are associated with a strong family history of cancer.
In the UK, more than 1 in 4 cancer deaths (over 25 per cent) are caused by smoking.
Breathing in other people’s smoke (passive smoking) also increases your risk of developing cancer.
Drinking alcohol increases your risk of mouth and throat cancers. But it is also linked to other cancers.
In general, the more you drink, the higher your risk. Your risk is even higher if you also smoke.
BEING OVERWEIGHT OR OBESE
Being overweight increases the risk of many types of cancer, including cancers of the bowel, kidney, womb and gullet (oesophagus). Women who are overweight and have been through the menopause also have a higher risk of breast cancer.
Keeping to a healthy body weight reduces your risk of cancer and other health problems, such as heart disease and diabetes.
Some 182,000 women are diagnosed with cancer in the UK every year, rising to 193,000 among men.
In the US, 970,000 men and 928,000 women have cancer confirmed annually.
Researchers from the NCI examined the rates of 21 types of cancer in 171,274 men and 122,826 women.
Participants were aged 50 to 71 and their records were monitored between 1995 and 2011.
The findings, published in the journal CANCER, show 17,951 cancers were detected among men, while just 8,742 were diagnosed among women.
Rates of thyroid and gallbladder cancer were higher among women, but the prevalence of all other cancers were higher among men.
They did not look at cancers that are sex-specific – like womb cancer or prostate cancer.
Men were 11 times more likely to develop oesophageal cancer and four times more at risk of stomach or throat cancer.
They also had a three times greater chance of being diagnosed with bladder cancer.
Further analysis found men were still more likely to develop cancer overall when other risk factors like smoking, alcohol intake and exposure to carcinogens were accounted for.
Scientists have previously pointed to higher rates of smoking, alcohol consumption and exposure to chemicals like asbestos in factories.
They also said men may be less likely to seek medical advice.
The team suggested the male sex hormone testosterone may increase the likelihood of skin, prostate and liver cancer among men by promoting cell growth.
Meanwhile, they said women appear to mount a stronger immune response against oncogenic infections — those which can cause cancer, such as hepatitis and HPV — which could lower their risk of some cancers in comparison to men.
And research suggests women have an extra copy of genes that protect against cancer compared to men, which could offer them further protection.
Study leader Dr Sarah Jackson, an epidemiologist at the National Cancer Institute, said: ‘Our results show that there are differences in cancer incidence that are not explained by environmental exposures alone.’
It comes as scientists today called for the NHS to offer all cancer patients genetic profiling to determine which drugs will be most effective against their tumour.
Biomarker tests should be offered to Britons as soon as they are diagnosed to shape their care and track how their illness evolves, according to a consensus statement from the Institute of Cancer Research and nine other organisations.
The tests look for genetic, protein or imaging ‘markers’ that identify weaknesses in cancers and can match patients to the treatment they are most likely to respond to.
It is ‘crucial’ that medics can use these tests but ‘regulatory processes and resources have not kept pace with the science’ so they are not always carried out.
Cancer Research UK, the Association of the British Pharmaceutical Industry, AstraZeneca and Leukemia UK also signed the statement.
The group called for genetic profiling at diagnosis and at regular intervals to become ‘standard’ within the NHS so patients receive personalized treatment.