Breast screening linked to higher (not lower!) mastectomy rates

Photo: National Cancer Institute

Breast screening is associated with a noticeable increase in mastectomy rates, despite women being told that screening reduces their risk of mastectomy, a study from Norway published on revealed.

The supposed aim of breast screening is to improve the timing of breast cancer diagnosis, thereby reducing the number of associated deaths. When women are encouraged to have a screening they’re also told that screening reduces the need for mastectomies and increases the potential for breast conserving treatment.

However, that isn’t what a team of researchers found. The Norwegian breast cancer screening program 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 (a precursor to cancer) 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.”

SOURCE: “Effect of mammography screening on surgical treatment for breast cancer in Norway: comparative analysis of cancer registry data” BMJ 2011; 343:d4692 Abstract online