Unmarried people also have poorer prospects of surviving the disease. NCRI researchers speculate that the difference may be due to “pester power” — married people have someone to help them demand treatment and provide support.

“It seems to be quite consistent across the cancers — that being married makes you more likely to have treatment and seems to improve your survival chances,” said Dr Harry Comber, NCRI director. “Even those who were widowed tend to do better than those who were never married. If there is another person in the equation, be it a spouse or a child, you’re more likely to be treated.”

The organisation collects information about every case of cancer diagnosed in Ireland. It is due to publish a report next month on the patterns of care and survival in the four types of cancer that cause the most deaths. Between them, lung, breast, prostate and bowel cancers account for almost half of cancer mortality. For each type, married patients tend to receive more treatment and have a better survival chance.

“One can speculate that having another person with you as an advocate is more likely to improve your access to care,” said Comber. “From my experience of being a GP, people with children probably have a different level of communication with the GP because there are a number of people engaged in the conversation rather than just two.

“Very often it is a tight decision whether to treat or not. Relatively small factors, such as a request by a family member, might well play an important part in that position.”

An investigation by the registry into cancer of the oesophagus, or gullet, which causes about 300 deaths a year, found that unmarried patients were 35% less likely to undergo surgery and 18% less likely to receive radiotherapy.

Comber said: “It may be that there are different cultural valuations on the lives of people with children, as against people who don’t have children.”

Deirdre Cronin-Fenton, the lead author of the study, which is published in the European Journal of Cancer, said: “Maybe it’s because a family is involved in treatment planning, or the support from a family could encourage someone to go for treatment. I would like to think that if it was my own parents in that situation, a doctor would listen to me shouting and roaring outside the room.”

The research was based on all upper gastrointestinal cancers diagnosed from 1994 to 2001, comprising more than 3,000 patients.

John Thaw, the British actor who played Inspector Morse, and Humphrey Bogart both died from oesophageal cancer. Those who contract the illness have a poor prognosis — the five-year survival rate is 9-13%.

The study found that older people are less likely to receive treatment. Only 20% of patients aged over 70 received surgery, compared with 51% of those under 70. Patients aged 60-69 were 26-43% less likely to be treated than those under 60.

Referring to differences in treatment due to marital status or age, the study concluded: “Inequitable treatment reduces survival and costs lives unnecessarily. Such disparities need to be addressed if survival and mortality rates for these cancers are to improve.”

It says apparent lower rates of surgery in Ireland, particularly in older patients, compared with America may be partly attributable to the lack of centralisation and specialisation of cancer services in the past. Between 1994 and 2001, patients were diagnosed and treated in many hospitals across the country, a large proportion of which had no specific expertise in oesophageal or gastric surgery, says the report.

Thirty-five per cent of patients received surgery, 35% radiotherapy and 24% chemotherapy. Chemotherapy and radiotherapy increased significantly during the study period, while surgery decreased.

Life expectancy after diagnosis increased slightly, rising from 5.9 months in 1994-1997 to 6.7 months in 1998-2001.

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