Demand and Outcome Projection of Breast Cancer Screening Guided by Quality Assurance Mammography Programme

Introduction. While mass screening for breast cancer with mammography in the reduction of mortality has been demonstrated and quality assurance mammography programme has been sponsored by International Breast Screening Network (IBSN) how the components of quality assurance mammography programme affect mortality or relevant outcomes has been rarely addressed. Demand and supply of manpower involved in breast cancer screening is also lacking given this programme.

Objective. This thesis aimed (1) to investigate the relationships of components of quality assurance programme of breast cancer screening presented in the IBSN to relate outcome; (2) to conduct an empirical survey in Taiwan following the design inherent from the components of (1); and (3) to assess the balance between supply and demand in association with population-based breast cancer screening following information on full-time equivalent (FTE) and capacity of clinical manpower obtained from (2).

Materials and Methods. Data on three dimensions related to pre-screening phase, screening phase and post-screening phase were extracted from literatures. The relationships of structural components, process components, and outcome components to main outcome were analyzed by ecological correlation study based on information collected from previous literatures by using backward correlation analysis. To make a better understanding of the components of quality assurance in Taiwan, we conducted a empirical survey aimed at target population from 85 institutions with mammography screening approved by Bureau of Health Promotion. In order to calculate the demand for mammography in national screening program, and disease burden, we used Markov cycle tree underpinning the five-sate Markov model for natural course of breast cancer to predict the required number. When dependent variables were of incidence of rare event, Poisson regression was conducted. For variables not of rare event, such as sensitivity, specificity, and prediction of positive value, etc., simple linear regression was used.
Results. After controlling the underlying incidence rate, the most significant structural components responsible for mortality was licensure of breast surgeon (regression coefficient=-0.23 (SE=0.08), P=0.007). The most significant process components was the number of view to be taken on mammography examination (regression coefficient=-0.28 (SE=0.026), P < 0.001). The most important outcome components was sensitivity (regression coefficient= -1.813 (SE=0.9241), P=0.0498).

Step-by-step backward analysis showed the proportion of node positive was determined by high interval cancer as percentage of the underlying incidence rate, which was, in turn, affected by sensitivity and nomenclature. Sensitivity was influenced by number of view to be taken and double reading. In addition, double reading and number of view to be taken play important role in situ detection rate.

Based on the results from the empirical survey on components of quality assurance and the developed prediction equation, we predicted 27% proportion of node positive and 14.4/100,000 mortality given significant components for both radiologist and breast surgeon, which is closed to, but slightly higher, than ,11.32/100,000 mortality as observed in Taiwan now.


Given 70% attendance rate, 1252544 mammograms are requested during six year period. The number of supply of manpower was 1120940 from breast surgeon and 4099788 from radiologists in six years. The demand of breast cancer for breast surgeon in treating disease was 21837 given 991 breast surgeons. Taking full-time equivalent time (FTE with only 10% breast surgeon get involved in breast cancer into account), approximately 99 FTE from breast surgeons will be involved in treating breast. This implies each FTE of breast surgeon may serve 222 breast cancers during six years.

In conclusion, a series of quantitative models pertaining to the relationships of components of quality assurance mammography programme to mortality or related outcome. These models together with the five-state Markov model were further applied to analysis of demand and supply of mass screening for breast cancer with mammography in Taiwan.