Women who are treated for early breast cancer that is detected through the UK national screening programme have as good a survival rate as the general population, the latest available figures show.
Audit data from the Association of Breast Surgery and the NHS’s breast screening programme show that women with small, early stage breast cancers that were detected in 1990-1 and who were categorised as having a good or excellent prognosis had the same five year survival rate as the general public. This type of breast cancer accounts for nearly two thirds (61%) of those detected through the screening programme. Survival rates were similar among women whose cancer was detected by screening in 2000-1.
The overall five year relative survival for women with breast cancer detected by screening rose from 93.6% in 1990-1 to 96.4% in 2000-1. This rise was due to an improvement in survival among women with more aggressive types of breast cancers and who were categorised as having a moderate or poor prognosis.
The latest available figures show that the UK screening programme detected 15 856 cancers in the nearly two million women screened between 1 April 2006 and 31 March 2007. This equates to a cancer detection rate of 8.1 cancers per 1000 women screened. Most women (93%) with breast cancer detected by screening were aged between 50 and 70 when they were invited for the screening that led to their diagnosis.
The UK breast cancer screening audit collects a range of data on women with breast cancer detected by screening, including the type of surgery they have, their adjuvant therapy, and survival.
Gill Lawrence, director of the West Midlands Cancer Intelligence Unit, which coordinated the audit, said, “Over the last 12 years the audit has mapped improvements in the quality of the NHS breast screening programme in the diagnosis and treatment of breast cancer. The data clearly demonstrate significant improvements in the quality of the service women receive.”
The data show a fall in the number of women needing surgery for a definitive diagnosis of breast cancer: 94% of cancers detected through the screening programme in 2006-7 were diagnosed without an operation.
“The treatment for breast cancer has improved,” Dr Lawrence said. “Less extensive surgery is needed now; in 2006-7 three out of four women with invasive cancers were treated by a breast conserving technique; and for the 6567 women with cancers smaller than 15 mm, fewer than one in five (18%) required a mastectomy.”
Peter Gøtzsche, director of the Nordic Cochrane Centre in Copenhagen, who has written extensively on breast cancer screening, said, “It is not the least surprising that women who had a small breast cancer diagnosed at screening and who were judged to have a good or excellent prognosis actually had a good or excellent prognosis. This is circular. It also ignores the fact that five year survival rates among people who had a cancer diagnosis made at screening are highly misleading, because of lead time and length biases.
“If these lesions are detected five years earlier than they would otherwise have been, it would be expected that the five year survival rate would be the same as that in the general population. Furthermore, many cancers detected at screening are overdiagnosed—that is, they would never have caused problems in the women’s remaining lifetime, but treating healthy citizens usually carries a good prognosis.
“To claim that the survival is the same as that in the general population is the same as saying that screening reduces breast cancer mortality by 100%. It is absurd that we can now see this ultimate exaggeration of the effect of screening in print, and sad that it was not meant to be just a joke for the Christmas issue."
Around one in three breast cancers diagnosed in England are detected by the NHS breast screening programme, which offers screening to women aged 50 to 70 years. The extension of the programme to women aged 47-73 will further increase the proportion of cancers detected by screening, suggested Julietta Patnick, director of the programme.
An Audit of Screen Detected Breast Cancers for the Year of Screening April 2006 to March 2007 is available at www.wmpho.org.uk/wmciu/documents/06-07%20BASO%20booklet%20final.pdf.