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  • br Note Arrow indicates screening guideline change in


    Note: Arrow indicates screening guideline change in 2009 for breast cancer. Lines were joinpoint regression lines. Among women aged 40−49 years:
    APC, annual percentage changes; J -, joinpoint regression line.
    which resulted in little change in the overall cancer inci-dence and stage distribution. The slightly increased inci-dence of metastatic breast cancer calls for close and active monitoring. However, the decreased APCs after 2009 in the incidence in metastatic cancer argues against the adverse contribution of the screening guideline change to the increased incidence. The decreased inci-dence in regional cancer in 2011−2014 among women aged 40−49 and 50−74 years, increased incidence in in situ cancer among women aged 40−49 years, relatively stable incidence in in situ cancer among women aged 50 −74 years, and similar stage distribution between 2006 −2009 and 2011−2014 also indicate that 9026-93-1 the screening guideline change is unlikely to lead to a meaningful increase in distant disease. The increased incidence in distant cancer in 2011−2004 may be the result of a con-tinuously increasing trend in metastatic breast cancer in the past few decades, which was mainly driven by changes in the distribution of risk factors in the U.S. and improved diagnostic imaging.33−35 Fast-growing breast cancer may emerge in less than 24 months and will not be captured by biennial screening.36 A significant pro-portion (13.8%) of diagnosed breast cancers are interval cancers diagnosed within 24 months after a negative screening mammogram. Kirsh et al.36 compared the stage and grade of breast cancer diagnosed in the interval 
    between mammogram screenings with screen-detected breast cancer and found that interval cancers missed by biennial screening were higher stages and grades com-pared with screen-detected cancers. Those fast-growing tumors may need more sensitive screening modalities for early detection. Whether detecting those tumors early will reduce cancer mortality also needs further investigation.
    A slight significant increase in breast cancer incidence in 2011−2014 was found among non-Hispanic black and Asian or Pacific Islander women. However, the dis-tribution of cancer stage stratified by race/ethnicity remained the same before and after the screening guide-line change. The observed increase in incidence among non-Hispanic black and Asian or Pacific Islander women is likely due to the already increasing incidence within stage. The increased screening utilization among blacks37−39 may contribute to the increased incidence. However, some studies suggest that the observed higher utilization of mammograms in blacks could partly be due to the fact that self-reported mammogram use tends to overestimate mammogram rates in blacks than in whites.40,41 Among non-Hispanic whites, the incidence in invasive breast cancer increased by about 2 per 100,000 women in 2011−2014 compared with 2006−2009; the statistical significance is likely due to the
    Note: Red arrow indicates screening guideline change in 2009 for breast cancer. Lines were joinpoint regression lines. Among women aged 40−49
    Stage of breast cancer, %
    Non-Hispanic white, %
    Asian or Pacific Islander, %
    Note: Data were from U.S. Cancer Statistics (USCS), the combined data from the Centers for Disease Control and Prevention’s (CDC’s) National Pro-gram for Cancer Registries (NPCR) and the National Cancer Institute’s (NCI’s) Surveillance, Epidemiology, and End Results (SEER) Program. When stage composition of breast cancer was calculated, number of cases in each stage was age-adjusted to the 2000 U.S. Standard Population. x2 test was used to compare stage composition between 2006−2009 and 2011−2014, and p-value for each test was >0.05.
    large sample size. Future studies are needed to examine the detailed impact of the screening guideline change on those racial/ethnic groups and to clarify the underlying contributors to the observed changes in incidence.
    A major strength of this study is that data were from the NPCR and SEER Incidence−USCS database, which covers the entire U.S. female population aged 40 −74 years and enables the generalizability of findings from this study. Data from USCS have high-quality information on breast cancer diagnosis date, stage, and sociodemographic characteristics, allowing for examina-tion of the impact of the screening guideline changes in various subpopulations. This study also has several lim-itations. Information about mammogram screening usage, screening pattern, and screening modality before breast cancer diagnosis was not available for partici-pants in the USCS database. Additionally, causal infer-ence cannot be concluded from these findings as this