[A comparative study of breast cancer mass screening and opportunistic screening in Chinese women].

To compare the population characteristics, the positive rate of screening, the detection rate of breast cancer, early diagnosis rate and the cost between the mass screening group and opportunistic screening group of breast cancer. This study is a prospective multicenter cohort study conducted from January 1, 2014 to December 31, 2016. The participants were enrolled for mass screening or opportunistic screening of breast cancer. After completing the questionnaire, all the participants received breast physical examination and breast ultrasound examination every year for 3 rounds by year. The participants' characteristics and screening results of the two groups were compared by χ test, Fisher exact test or Wilcoxon rank-sum test. A total of 20 080 subjects were enrolled. In the mass screening group, 9 434 (100%), 8 111 (85.98%) and 3 940 (41.76%) cases completed the 3 rounds of screening, and 10 646 (100%), 6 209 (58.32%) and 2 988 (28.07%) cases in the opportunistic screening group, respectively. In the opportunistic screening group, the proportions of less than 3 months lactation (1 275/9 796 1 061/8 860, χ²=4.597, =0.032), non-fertility (850/10 646 574/9 434, χ²=27.400, <0.01), abortion history (6 384/10 646 5 062/9 434, χ²=81.232, <0.01), postmenopausal (2 776/10 646 2 217/9 434, χ²=17.757, <0.01), long-term oral contraceptives(>6 months) (171/10 646 77/9 434, χ²=25.593, <0.01) and family history of breast cancer in first-degree relatives (464/10 646 236/9 434, χ²=51.257, <0.01) were significantly higher than those in mass screening group. The positive rate of screening (514/10 646 128/9 434, χ²=194.736, <0.01), the detection rate of breast cancer (158/10 646 13/9 434, χ²=107.374, <0.01), and positive rate of biopsy (158/452 13/87, χ²=13.491, <0.01) in the opportunistic screening group were significantly higher than those of the mass screening group. The early diagnosis rate of the mass screening group was significantly higher than the opportunistic screening group (10/12 66/141, χ²=5.902, =0.015). The average cost for detecting each breast cancer case of the mass screening group was 215 038 CNY, which was 13.6 times of the opportunistic screening group (15 799 CNY/case). In the opportunistic screening group, the positive rate of biopsy in primary hospitals was significantly lower than that in large-volume hospitals (79/267 79/185, χ²=8.267, =0.004), but there was no significant difference in the mass screening group (6/37 7/50, χ²=0.082, =0.774). Breast cancer screening can improve early detection rate. Compared with the mass screening mode, the opportunistic screening mode has the advantages of higher proportion of high-risk factors, higher positive rate of screening, higher detection rate of breast cancer, higher positive rate of biopsy, and lower cost of screening. However, the early diagnosis rate of breast cancer of opportunistic screening is lower than that of mass screening. The positive rate of opportunistic screening in primary hospitals is lower than that of large-volume hospitals. The two screening modes have their own advantages and should be chosen according to local conditions of different regions in China.