Breast screening is associated with an increase in mastectomy rates, despite women being told that screening reduces their risk of mastectomy.
This is the finding from a study from Norway published on bmj.com.
The aim of breast screening is to improve the timing of breast cancer diagnosis, thereby reducing the number of associated deaths. A potential additional benefit often stated in invitations to screening is that screening reduces the need for mastectomies and increases the potential for breast conserving treatment.
The Norwegian breast cancer screening programme started in 1996 in four counties, and from 1999 to 2004 the remaining 15 counties were successively included.
The researchers used national cancer data for 35,408 women aged 40 to 79 years diagnosed with invasive breast cancer or ductal carcinoma in situ from 1993 to 2008.
From the pre-screening period (1993-95) to the screening introduction phase (1996-2004), the annual mastectomy rate increased by 9%, from 156 to 167 per 100,000 women in the age group invited to screening (50-69 years). In contrast, the mastectomy rates fell by 17% in non invited women aged 40-49 years.
In relative terms, this corresponds to a 31% increased risk of undergoing mastectomy in women invited to screening compared with the non-invited younger age group. Mastectomy rates also fell by 13% in non invited older women (aged 70-79 years).
More recently (2005-08), mastectomy rates declined across all age groups, but mostly for the non-screened age groups. This, say the authors, is most likely due to changes in surgical policy.
They conclude: “Mammography screening is associated with a noticeable increase in breast surgery rates. In contrast with what has been claimed in invitations to screening and on websites supported by numerous governmental screening institutions and cancer charities, screening does not lead to a reduction in mastectomy rates.”
Speaking to OnMedica, author Paal Suhrke, pathologist at Oslo University Hospital said: “A woman who gets a cancer diagnosis has to be offered the standard treatment. Over-diagnosis is seen when you look at incidence rates of breast cancer when screening is introduced. Then you will see that the incidence rates increases by 50%, most of these cases are over-diagnosed cases - cases which in the absence of screening would not have been detected. So because of this there is no distinction between necessary mastectomies and mastectomies carried out due to over-diagnosis. “