Women over 50 who have been treated for a precursor to breast cancer known as ductal carcinoma in situ (DCIS) are more likely live another ten years than women in the general population, according to research presented by the Netherlands Cancer Institute.
DCIS diagnoses are increasing as breast screening becomes more common. The pre-cancerous cells cannot spread around the body, but can develop into full-blown invasive breast cancer if untreated.
The research team studied data on almost 10,000 Dutch women who were diagnosed with DCIS between 1989 and 2004. They compared their death rates with expected mortality in the general population over 10 years, and found that women over 50 who had been treated for the condition had a 10 per cent lower risk of dying from all causes, and a higher risk of dying from breast cancer.
Dr Lotte Elshof, who analysed the data, told the European Cancer Congress 2017: ‘Being diagnosed with DCIS can be extremely distressing, and research indicates that many women overestimate the risks involved and are confused about treatment. This study should provide reassurance that a diagnosis of DCIS does not raise the risk of dying.
‘It might seem surprising that this group of women actually has a lower mortality rate than the general population. However, the vast majority would have been diagnosed via breast screening, which suggests they may be health-conscious and well enough to participate in screening.’
The researchers are beginning an international collaboration with scientists in Britain and the US. They hope that a larger data pool will allow them to understand why some cases of DCIS develop into invasive cancer, while others do not.
In situ means in place and so by definition is pre-cancerous, or potentially cancerous. About 80 per cent of the time it is picked up by breast cancer screening, before it can cause symptoms, eg, pain or a lump. However, it does encompass a broad range of lesions, from benign to aggressive, and there is no way of predicting which will become truly cancerous. Therefore there is no way of knowing which will require treatment. If left untreated about 30 per cent of women will go on to develop symptomatic breast cancer. Of those diagnosed and treated, only two per cent will die at 10 years. To add to the confusion, some academic institutions define DCIS as a form of cancer and others do not.
The study suggests that although women diagnosed with DCIS have a slightly higher rate of death from breast cancer, they have a slightly lower risk of dying from any other cause compared to the general population and this is in spite of the possible complications and side effects of treatment.
This makes sense, as a pre-cancer ‘scare’ may well lead to women making lifestyle changes to reduce their risk of a bigger killer of women, cardiovascular disease — that is, by stopping smoking, taking regular exercise, reducing alcohol consumption and eating a healthier diet.
This is supported by the fact that such women were less likely to die from cardiovascular and respiratory disease and also other cancers, such as of the digestive system.
A confounding factor is that women who partake in screening may be healthier and wealthier than those who don’t or indeed the general population at large. Such factors will need to be taken into account before firm conclusions are made. The Dutch team who conducted the study are planning further research.
It’s a thought-provoking study, which should give comfort to women diagnosed with DCIS. But as ever with research, the devil is in the data.