Health

Wednesday 1 October 2014

'These are exciting times for cancer treatment but there's still a long way to go'

Consultant oncologist Professor John Crown

Most of the news about cancer is actually very good. Let's get the bad stuff out of the way first. Cancer is getting more common in Ireland and most western countries, but most of this increase is down to the fact that people are living longer, long enough to get cancer, a disease which disproportionately affects the middle-aged and elderly.

Specific lifestyle factors are important causes of some cancers. The sheer danger of smoking puts all other avoidable risk factors in the shade. The frequency of lung cancer in men began dropping when large numbers of men stopped smoking. Smoking in women continued to rise, and so did lung cancer, soon overtaking breast cancer as a cause of death. Smoking is also a major contributor to cancers of the mouth, tongue, throat, pancreas and bladder.

No cancer treatment yet discovered or likely to be discovered soon, would have remotely as big an impact on cancer death rates as would complete smoking cessation.

We need food to live, but dietary excess rivals and may exceed smoking as a cause of ill-health.

Societies where people have higher food and calorie intakes, and increased levels of obesity, also tend to get more cancer. The same good 'diet and exercise' advice that we should follow to prevent heart disease and stroke also reduces cancer risk.

Excess alcohol increases the risk of several cancers.

We are also seeing an alarming increase in malignant melanoma, a usually curable, but all-too-often fatal type of skin cancer. This disease is strongly related to sun exposure, and in particular to sunburn. The increase in melanoma is particularly striking in Ireland, where our pale skin and tendency to get short highly intense bursts of exposure might pose particular risk.

Things which have NOT been shown to increase cancer include power pylons, Sellafield, insecticides and fluoridated water.

Research has made unbelievable strides in recent years. The five-year survival rate for cancer patients in the USA has nearly doubled since the 1960s, due to a combination of earlier diagnosis and improved treatment.

'Screening' (ie testing apparently healthy people who have no worrying symptoms) has a proven role in only a limited number of cancer types, prominently cervix cancer where 'Pap' smears have resulted in huge declines in mortality. The impact of screening X-rays for breast cancer ('mammography') is not as big as was hoped, but it does reduce the number of deaths from cancer in screened populations.

The best chance to cure most cancers is still provided by early diagnosis and expert surgery, or in some cases localised ray treatment (radiotherapy). For other patients where the disease has spread and can no longer be cut out, radiotherapy and chemotherapy have had important impacts in improving cancer survival rates. For some uncommon cancers, like lymphoma and testicular cancer, chemotherapy routinely cures. Gratifyingly, childhood cancers are particularly sensitive to chemotherapy, and are frequently cured.

There have also been substantial improvements in the chemotherapy of the more common cancers, but sadly, no new members have joined the list of 'cancers curable by chemotherapy' in recent decades. There is a sense that chemotherapy might have probably 'maxed out' in terms of future improvements.

Most research in cancer treatment now focuses on identifying specific 'targets' for new cancer treatments. We have moved as it were from blunderbusses or scatterguns (chemotherapy) to smart bombs. Such targeted therapies are now making important contributions to the treatment of several cancers.

As a young cancer specialist in training, the disease I hated more than any was CML-chronic myeloid leukaemia. Patients seemed fairly healthy, but ticking away in their bone marrow was an inevitably fatal leukaemia time bomb, a virtually 100pc chance of dying within three years. Unbelievable research unravelled the molecular booby-trap in the cancer cells, and within a few years a simple tablet treatment transformed this condition into one where survival for decades became the norm.

Similarly a drug called Herceptin has transformed the treatment of some breast cancers.

Newer immune treatments are also producing spectacular results in some patients with melanoma.

These are exciting times and I am very confident that there will be steady progress in cancer research in coming years. The Irish Cooperative Oncology Research Group (ICORG) will continue to provide a vehicle to bring new cancer treatments to patients throughout Ireland.

In terms of understanding cancer and laying a groundwork for new cancer treatments, science has reached a height that we thought might never be achieved. A cautionary note – the view from the top has included panoramas of other mountains.

We've come a long way, but have a long way to go.

JOHN CROWN IS A LEADING CONSULTANT ONCOLOGIST AND SITS AS AN INDEPENDENT MEMBER OF THE SEANAD

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