Abstract P4-02-15: The effect of the 2013 American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines in HER2 positivity rates among women with breast cancer in SEER registries

Abstract

Abstract Introduction: The American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) revised the HER2 testing guidelines in breast cancer (BC) which was published in December 2013, practically becoming effective in 2014. Since then, many studies reported a significant increase in HER2 positivity rate in BC. Although HER2 has been routinely evaluated in BC for over a decade, HER2 status was not included in SEER registries until 2010. The aim of this study is to look at the effect of the 2013 ASCO/CAP guidelines on HER2 status in the SEER database that captures approximately 28% of all cancers in the US. Material and Methods. Using data from 18 SEER cancer registries between the years of 2010-2015 when HER2 status for breast cancers was available, women with invasive BC were identified and their HER2 status and race was recorded. The Chi-square test was used to test the significance between positive proportions before and after the new ASCO/CAP guidelines were effective. Logistic regression was used to test if the changes in positivity rate were the same among different races. All calculations were made after excluding cases with unknown/missing HER2 status. Results: We identified 376,278 women diagnosed with invasive BC between the years 2010-2015. HER2 positivity before 2014 (2010-2013) was 14.4% compared to 15.6% after 2013 (2014-2015) (p<0.001). HER2 positivity increased in all races after 2013. There was no significant difference in the increase of HER2 positivity between whites and blacks after the new guidelines went into effect. Unknown/missing HER2 status continually decreased over the study period from 7.4% in 2010 to 5.3% in 2015. Overall unknown/missing HER2 was significantly different among races: 6.5% in whites; 7.1% in blacks; and 6.2% in other races (p<0.01). Conclusion: Revised ASCO/CAP HER2 guidelines significantly increased HER2 positivity rates in SEER registries from 14.4% to 15.6% after implementation started in 2014. HER2 positivity increased in all races after 2013. Unknown/missing HER2 status is significantly different among different races. Blacks have highest unknown/ missing HER2 status in SEER registries. Citation Format: Wang XK, Hu N, Herget K, Cinbis BR, Gulbahce EH. The effect of the 2013 American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines in HER2 positivity rates among women with breast cancer in SEER registries [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-02-15.