Screening for breast cancer with mammography

Screening uses a test to check people who have no symptoms of a particular disease, to identify people who might have that disease and to allow it to be treated at an early stage when a cure is more likely. Mammography uses X-ray to try to find early breast cancers before a lump can be felt. Many countries have introduced mammography screening for women aged 50 to 69. The review includes seven trials involving a total of half a million women.

The review found that mammography screening for breast cancer likely reduces breast cancer mortality, but the magnitude of the effect is uncertain and screening will also result in some women getting a cancer diagnosis even though their cancer would not have led to death or sickness. Currently, it is not possible to tell which women these are, and they are therefore likely to have breasts and lumps removed and to receive radiotherapy unnecessarily. Based on all trials, the reduction in breast cancer mortality is 20%, but as the effect is lower in the highest quality trials, a more reasonable estimate is a 15% relative risk reduction.

Based on the risk level of women in these trials, the absolute risk reduction was 0.05%. Screening also leads to overdiagnosis and overtreatment, with an estimated 30% increase, or an absolute risk increase of 0.5%. This means that for every 2000 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.

http://www.cochrane.org/reviews/en/ab001877.html

For this study, researchers in the province of British Columbia analyzed the records of nearly 2,600 breast cancer patients.

"Our findings can reassure women with early-stage breast cancer that it is okay to take some time before their start chemotherapy to gather information and be actively involved in treatment decision-making. These steps have been shown to reduce anxiety and depression associated with breast cancer," study lead author Dr. Caroline Lohrisch, a medical oncologist with the BC Cancer Agency, said in a prepared statement.

"However, to achieve the full benefit of chemotherapy, patients should not delay further, and should ensure that they start treatment within three months of surgery," she added.

The women in this study received chemotherapy after surgery for stage I and II breast cancer between 1989 and 1998. Among women who started chemotherapy within four weeks of surgery, 84 percent were alive five years after their breast cancer diagnosis. Survival rates were similar for women who began chemotherapy four to eight weeks (85 percent) and eight to 12 weeks (89 percent) after surgery.

But the study found that five-year survival dropped to 78 percent among women who didn't start chemotherapy until more than 12 weeks after breast cancer surgery. These women also had a higher rate of cancer recurrence (31 percent) than women who started chemotherapy within 12 weeks (18 percent to 26 percent).

Links to abstract and article in the Journal of Clinical Oncology

http://www.jco.org/cgi/content/abstract/JCO.2005.01.6089v1