[The role of epidemiological quality parameters in a mammography screening programme]

[Determination of interval cancer rates in the German mammography screening program using population-based cancer registry data]

GOAL

The evaluation of interval cancers (ICA) and false-negative diagnoses (FND) is important for the quality assurance of the mammography screening program (MSP) for women aged 50-69 years. We aimed to investigate ICA in the states of Lower Saxony (NDS) and North Rhine-Westphalia (NRW). ICA could be identified by record linkage of data from screening attendees (TN) with data from population-based cancer registries. The frequencies of ICA and FND are described, and problems in the categorization of ICA according to EU guidelines are discussed.

METHODS

Record linkage in the cancer registries was performed with the encrypted data from 83,724 TN in NDS and 885,940 TN in NRW. ICA were identified; in NDS, ICA were categorized by the regional MSP reference center.

RESULTS

In all, 208 ICA in NDS and 2.018 ICA in NRW were ascertained. In relation to the regional background incidence rate (IR), the relative ICA rates were 22.5%/26.7% in the first year after screening (recommendation of EU guidelines <30% of IR) and 55.6%/54.2% in the second year after screening (recommendation of EU guidelines <50% of IR). It was found that 17.3% of all categorized ICA in NDS were FND (recommendation of EU guidelines <20%).

DISCUSSION

The relative ICA rates for the 2-year interval are consistent with the recommendations of the EU guidelines. Unlike in NDS, the categorization of ICA was not possible in NRW. The MSP needs the diagnostic mammograms of all ICA in order to identify FND. However, data protection regulations are hindering this process and nationwide comparability of FND is therefore not guaranteed. In NDS, the state government has enacted laws to facilitate the transfer of diagnostic mammograms to the MSP. There is need for this sort of action in other federal states too.

Benefit and risk of mammography screening: considerations from an epidemiological viewpoint

INTRODUCTION

An organized mammography screening program is being implemented in Germany since the end of 2005. Even before its inception, a heated debate surrounded the question of how to communicate its rationale appropriately.

METHODS

Selective literature review identifying facts relevant to informing decision making about mammography attendance.

RESULTS

Decision making about individual attendance for mammography screening is crucially dependent on the reduction of risk of death from breast cancer for a diseased woman. This can be communicated in the following way: out of 100 women with a diagnosis of breast cancer 31 will die within the following 10 years without screening and 20 with screening (35% fewer).

DISCUSSION

The actuarial concept of risk is defined by the probability of the undesired event multiplied by the expected magnitude of loss. This approach appears more appropriate for the appraisal of risk in the context of mammography screening than a pure event probability. It could help understand why women attend screening even if they perceive the risk of getting breast cancer as low--namely, that they rank the consequences of getting the disease as highly significant for themselves and others in their social environment.

[Mammography screening]

Exclusive biannual mammography screening for women ages 50-69 years reduces the mortality from breast cancer among participants by 35%. Compared with 50% of clinically detected cancers, only 20% of carcinomas detected in screening have nodal metastases, and up to 55% of screening carcinomas are in the T1 stage of "minimal cancer." In many European countries (including Sweden, Norway, the Netherlands, and Great Britain), mammography screening programmes have been established for more than 10 years. In Germany, the aim is to establish, by 2008, a nationwide organised programme on the basis of the European Guidelines for Quality Assurance. This goal requires 80-100 mammography screening units. The first screening units went into use in 2005. Women between 50 and 69 years are invited to participate in 2-year intervals.