Three-quarters of cancer patients who also have clinical depression are not currently receiving any treatment for depression, a study has found.

Researchers from Oxford and Edinburgh universities also said that those who are receiving care could have their quality of life improved by a new medical programme, 10 years in the making, which they say has proved more effective at tackling clinical depression than existing treatment in a clinical trial.

The trial of 500 patients with a good cancer prognosis, details of which were published in the Lancet on Thursday, found that 62% of patients who took part in the Depression Care for People with Cancer (DCPC) programme, which is delivered by specially trained cancer nurses supervised by psychiatrists, responded to treatment (at least a 50% reduction in the severity of their depression) compared with 17% who received the usual care.

Clinical depression was much more prevalent among cancer patients than in the general population, where around 2% of people suffer from the mental illness at any point in time. Among cancer patients, clinical depression ranged from 13% in people with lung cancer to 6% in people with genitourinary cancer.

The study's lead author Michael Sharpe, from Oxford University, said: "Major depression is really quite common in people with cancer and the perhaps surprising finding is that most of it goes untreated. The outcome with usual care is poor.

"We've described a new approach to managing depressed cancer patients that is based on the shortcomings of usual care, and integrated with cancer care, that really has quite spectacular effects in the good-prognosis patients and also has efficacy in the poor-prognosis patients."

Study leader, Jane Walker, described the 45 percentage point difference to the usual care as a "huge treatment effect", rarely seen in medical trials. "Also anxiety, pain, fatigue, were all a lot better with this treatment programme," said Walker. "They were much more able to function and their quality of life was a lot better."

A second trial on Scottish patients, details of which were published in the Lancet Oncology found that a version of the DCPC adapted for use with people with lung cancer, which has a poor prognosis, also delivered significantly greater improvement in depression than those who received the usual care during 32 weeks of follow-up.

The researchers said that their focus was on quality of life rather than length of life, but there is some evidence that people with cancer who also have depression have a reduced survival rate. This is believed to be because they tend to have reduced adherence to their treatment programme.

The DCPC differs from usual care in that it is integrated with the patient's cancer care, includes both antidepressants and psychological treatment and includes careful monitoring, allowing the treatment to be adapted over time to the individual's needs. The researchers suggested that integrated care has not been available previously because of the separation of physical and mental health services in the UK. At £613 per patient, they argue that DCPC is cost-effective.

Usually, care at present involves prescription of antidepressants, with little follow-up, or a referral to mental health services for assessment for psychological treatment, the researchers said. Out of people with cancer and clinical depression, 24% were found to be taking antidepressants and 5% were seeing a health professional, a separate study by the same team published in the Lancet Psychiatry found. Overall, 73% of more than 21,000 patients attending cancer clinics in Scotland with cancer and clinical depression were not receiving any treatment. All three studies were funded by Cancer Research UK and the Scottish government.