C. Huang1, C. Fann1, G. Hsu1, M. Ho1, S. Chen1, S. Chen1, C. Chen1, S. Sheen-Chen1, H. Chang1, D. Yeh1, D. Chen1, K. Chang1, S. Kon1, A. Ming-Fang1, Y.、L. Chen1, S. Chiu1, H. Chen1 1Breast Cancer Screening Group of Taiwan Breast Cancer Consortium
Background: The efficacy of mammography screening in young women aged 40-49 is not established. As the sensitivity of mammography is poorer in dense breasts, commonly seen in young women, and the performance of ultrasound is not affected by breast density, we conducted a randomized trial to investigate whether annual screening with alternating mammography and ultrasound could detect more breast cancers and earlier than no screening.
Methods:
A total of 79,690 women aged 40-49 years were invited from community in Taiwan since late 2003. These participants were randomly assigned to the study group (n=40127) to receive alternating mammography or ultrasound annually or to the control group (n=39563). The study group was further randomized to receive either mammography (the M-U group) or ultrasound (the U-M group) for the first year screen. Detection rate and sensitivity using one minus annual incidence rate of interval cancer as a percentage of the control group were compared between mammography and ultrasound based on two cross -over designed group. The excess of breast cancers detected by the combined study groups in comparison with the control group was estimated by the comparison of two cumulative incidence of breast cancer curves. The relative rate of reducing stageII+ breast cancers was also estimated using the Poisson regression model.
Results:
The attendance rate of the first -year screen was 59% (11921/20040) and 56% (11249/20087) for the M-U group and the U -M group, respectively. The repeated attendance rate of both groups was 85% in the second round and 91% in the third round. In the first round of screening, the detection rate of breast cancer for the mammography group (0.34%) was 1.5 -fold compared with the ultrasound group (0.22%). In the first three rounds, we found that the detection rates for invasive caner or all cancer by mammography were higher than their counterparts with ultrasound. The alternative screening tool design enables us to estimate the additional benefit of ultrasound, 28.6% for all breast cancer and 38.6% for invasive carcinoma. It was noted that in the fourth round, ultrasound can detect more invasive cancer with detection rate of 0.15% than 3 mammography (0.08%), as well as more early invasive cancers (stage I) (7 by ultrasound vs. 3 by mammography), although mammography consistently detects more in situ cancers than ultrasound (12 vs. 1). The combined study groups led to a marginally statistically significant 18% (Relative rate=0.82 (95% CI: 0.65 -1.02)) reduction of incidence in stageII+ breast cancers compared with the control group.
Conclusion:
The current randomized controlled trial not only demonstrated higher detection rate and performance using mammography but also indicated the complementary role of ultrasound applied to young Taiwanese women. These findings provide valuable information on mass screening modality for young women in Asian country.