At the present time in the UK the national breast cancer screening programme offers women between the ages of 50 and 65, the chance of having an x-ray of their breasts, called a mammogram, once every three years.  (In some parts of the country the upper age limit is being increased to include women up to 70.)

There is good evidence that mammographic screening of women older than 50 does detect breast cancers at an earlier stage, when treatment is more likely to be successful.  As a result there is no doubt that the cure rate for breast cancer has increased and many women’s lives have been saved as a result.

The value of screening with routine mammograms in younger women is far less certain.  One reason for this is that in women who have not yet reached the menopause their breast tissue tends to be firmer and denser than in older women.  This makes it more difficult for small cancers to be seen on a mammogram and the chances of ‘missing’ a cancer are much higher.

To clear up this important question very large clinical trials are in progress to try and decide whether mammograms may help in  younger women. 

Recently a study in Canada, involving over 50,000 women between the ages of 40 to 49 years has looked at this question.  The women were divided into two groups.  One group had screening with mammograms every year plus an examination of their breast and instructions on how to carry out breast examination for themselves.  The other group simply had a single breast examination and instruction on how to carry out self-examination. 

The results showed that although slightly more cancers were discovered in the women who had mammography, overall the number of death due breast cancer was virtually the same in the two groups (105 in the ‘mammogram’ group, 108 in the others).  So the study concluded that annual screening on women under 50 had no effect on improving the outcome if a breast cancer occurred.

This is a very important question and most experts would agree that it cannot be answered by a single study. At the present time there  is a similar trial to the one done in Canada being carried out in the UK.  When the results of this are known it will help to give a more definite answer on the value of mammographic screening in younger women.

References:

• Miller AB et al. The Canadian national breast screening study 1: breast cancer mortality after 11 to 16 years of follow-up. A randomized screening trial of mammography in women aged 40 to 49. Annals of Internal Medicine 2002, 137: 305-12
• Spurgeon D, Annual mammography in women in their 40s does not cut death rate.  BMJ 2002, 325: 563
• Working Group International Agency for research on Cancer (2002) IARC Handbook of cancer prevention: Volume 7; Breast Cancer Screening. Lyon (IARC press)