Current status of breast cancer undetected by mammography in population-based breast cancer screening and associated factors

Abstract

Objective This study aimed to promote the application of mammography (MMG) screening without performing a clinical breast examination (CBE). It examined population-based screening data, including history taking findings, to elucidate the status of breast cancer cases, detected solely by CBE, and to reveal the factors associated with breast cancer. Through this, it explored alternative methods for evaluating breast cancer cases, undetected by MMG, when CBE is omitted.Methods The linked anonymized data from women, who underwent breast cancer screening in 2014, 2016, or 2017, were prepared. The data were obtained from the Nishinomiya City database. Breast cancer, undetected by MMG, were defined as breast cancer cases diagnosed by close examination based on CBE only (MMG findings were category 2 or lower, with no abnormalities). To assess the quality of breast cancer screening, process indices were calculated for the overall population, and for patients indicated for close examination based on CBE but not MMG. The association of breast cancer with each factor was statistically analyzed (χ2 test, etc.).Results In total, 13,504 women underwent breast cancer screening. Close examination was required in 1,247 women (9.2%). Breast cancer was diagnosed in 44 women (3.5%), including four, who had breast cancer undetected by MMG. All of the process indices satisfied the acceptable values. Three of the four women with breast cancer, undetected by MMG, noticed a lump. Breast cancer was significantly associated with "subjective symptoms". The presence of a "lump" and "nipple discharge" were significantly more common in breast cancer patients.Conclusion Three of the four breast cancer cases, undetected by MMG screening, had a subjective symptom (lump). There was a significant association between subjective symptoms (lump and nipple discharge) and breast cancer. To avoid missing breast cancer, undetected by MMG alone, these symptoms should be especially evaluated in women to compensate for the omission of a CBE. This can be achieved by encouraging women experiencing symptoms to seek consult, performing a thorough history-taking and observation, engaging in multidisciplinary collaboration (communication from medical staff to physicians), and promoting breast awareness.