Mammographic screening for breast cancer

Dr Joe Psaila (The Sunday Times, August 3) concluded that my piece about screening for breast cancer is misleading and scientifically unfounded. Dr Nadine Delicata (August 10) stated that analysis of current scientific evidence based on the benefits and cost-effectiveness of breast cancer screening is in favour of organised screening programmes.

Data of the studies by Gotzsche and Nielsen (2001) which I quoted were updated in July 2006 (Screening for breast cancer with mammography, Cochrane Database of Systemic Reviews 2006, Issue 3). These recent reviews, which included seven trials involving half a million women, found that although mammography screening for breast cancer likely reduces breast cancer mortality, the magnitude of the effect is uncertain and screening will also result in some women being diagnosed with cancer even though their cancer would not have led to death, or sickness.

It is not currently possible to tell who these women are, and they are therefore likely to have breasts and lumps removed and to receive radiotherapy unnecessarily. The percentage in the reduction in breast cancer mortality depends on the quality of the trials.

The figures quoted by Dr Psaila from the Swedish Report, 2005, varies from 21 per cent to 25 per cent. According to the 2006 review, the reduction in breast cancer mortality is 20 per cent, but as the effect is lower in the highest quality trials, a more reasonable estimate is a 15 per cent relative risk reduction.

Based on the risk level of women in these trials, the absolute risk reduction was 0.05 per cent. Screening also leads to over-diagnosis and over-treatment, with an estimated 30 per cent increase, or an absolute risk increase of 0.5 per cent. This means that for every 2,000 women invited for screening throughout 10 years, one will have her life prolonged.

In addition, 10 healthy women, who would not have been diagnosed if there had not been screening, will be diagnosed as breast cancer patients and will be treated unnecessarily. It is thus not clear whether screening does more good than harm.

Dr Delicata stated that there is clear scientific evidence that organised screening 'shifts' the stage of cancer presentation. This is a false claim. In the audit of surgery for the National Health Service Breast Screening Programme (NHSBSP), it was reported that between 20 and 50 per cent of cases of duct carcinoma in situ (DCIS) ('early breast cancer'?) end up having their breasts completely removed (mastectomy).

The net effect of NHSBSP on invasive surgical procedures on the breast in England and Wales has been an increase of just under 20 per cent mastectomy rates for invasive breast cancer and over 400 per cent mastectomy rates for DCIS since 1990 corrected for any changes in demography of the population (Douek and Baum, 2003).

Both colleagues emphasised the Christian needs to care, in particular, for the more vulnerable sectors. My aim is not to shoot down the programme but to present the other side of the coin using evidence-based medicine. On the other hand, we all know the pitiful state in which the public primary care is and the strain this is causing on our new hospital.

We must set our priorities, and I believe that our health system cannot improve at this point in time unless the primary sector is revitalised and the necessary changes are implemented. These changes need funds too. Primary care really can save lives, and money. If ever I heard of a win-win situation, this is it (Haslam, 2008).