In our study, the median age of breast cancer survivors and non-cancer controls were 53 years without existence of significance. While there were significant difference of the metabolism index between the two groups. Both the BMI and waist circumferences of BCS were significantly higher than those of non-cancer controls (Table 1). Previous studies have established the evidence that greater weight relates to the increased risk of breast cancer and prevails in BCS as well [10, 17], and waist circumferences, a more precise reflection of body fatty distribution, is dose-independent associated with breast cancer . Among BCS, the mean waist circumference was 82.3 cm, which met the criteria of central obesity defined as excess waist circumference over 80 cm in Asian female. In addition to the risks mentioned, the elevated fasting glucose level and triglycerides in BCS indicated the metabolism disorder as well. The existence of metabolism disorder in BCS may explain the obvious disparity of hepatic steatosis and further MAFLD prevalence between breast cancer survivors and non-cancer controls.
Jeffrey Browning et.al, using proton magnetic resonance spectroscopy (proton-MRS), found the hepatic steatosis was presented in 31% of 2,287 urban participants in the United States.  While our study found 22.4% of female general population was diagnosed with HS, consistent with another Chinese research that 20.59% female in Shanghai were diagnosed with HS . The disparity might be attributable to the different ethnic groups and detection methods. In breast cancer survivors, the prevalence of HS (41.8%) according to liver ultrasonography was significantly higher than that of healthcare population and even higher than Browning’s results. The shared risk factors between breast cancer and HS, synergistically coupled with the existence of metabolism disorder in BCS might be associated with the higher prevalence of HS. In addition, 43% of breast cancer patients treated with tamoxifen are reported to develop steatosis as well.  Researches have revealed that 20-year absolute excess risk of mortality was 10.7% higher with steatosis,  and thus general and breast cancer population in particular should be alerted the occurrence of hepatic steatosis and informed the importance of the reversing hepatic steatosis. The public health efforts focused on the prevention and control measures of HS require knowledge on its prevalence and in order to explore the specific and accurate prevalence rate of HS in BCS, we implemented liver ultrasound elastography. Liver ultrasound elastography was regarded as the more sensitive tool for HS diagnosis than conventional liver ultrasonography [15, 22]. We used FibroTouch, a new generation of transient elastography, and more HS in the same BCS was detected (69.5%). The diagnosis of MAFLD requires pre-diagnosis of HS according to the 2020 international consensus, and the high prevalence of HS directly reflected the current epidemiology of MAFLD. In our study, MAFLD was presented in 39.5% in BCS via liver ultrasonography detection, while a previous Korean reported 30.0% rate of NAFLD occurrence in breast cancer patients . Since NAFLD diagnosis necessitates the exclusion of “excess” alcoholic consumption, which is not necessary for the diagnosis of MAFLD, MAFLD prevalence is not equal to NAFLD prevalence and ought to be higher despite of the same detection modality. And using Fibrotouch, we found an even higher prevalence of MAFLD (63.5%) among BCS, and the prevalence of HS and MAFLD based on USE rose to 80.0% and 73.3%, respectively, which to some extent reflected more accurate situation involving MAFLD prevalence in cancer population. As a rapid increase disease worldwide, MAFLD does not draw surgeon’s attention, and despite of the high frequency in breast cancer patients, the recognition that MAFLD has occurred is often delayed or even neglected in breast specialists. According to the guidelines, liver ultrasonography is not recommended for routine follow-up in a asymptomatic patient with no specific findings on clinical examination[24, 25]. While HS usually present with no symptoms, therefore liver ultrasonography ultrasound for screening of BCS with HS might be absent, which leads to the failure of early prevention of HS and increases the risk of progress to MAFLD. MAFLD is highly linked to a rise in the risk of cardiovascular disease (CVD), and BCS are at a greater risk for CVD-related mortality. The ignorance of HS and MAFLD seriously affected the prognosis of BCS.Considering the frequency of HS and MAFLD in breast cancer survivors, liver ultrasonography screening for HS should be enhanced and further, the liver ultrasound elastography detection should be promoted and constituted into the routine screening items.
Our study has the strengths of an initial use of liver ultrasound elastography to detect the HS prevalence among breast cancer survivors. However, it also has a few limitations. First, all subjects were Chinese. Further studies are required to shed light on the epidemiology of MAFLD. Second, in light of the relatively small sample size, we obtained the HS prevalence among breast cancer survivors without the stratification of therapy methods and molecular types of breast cancer, otherwise we could obtain a more specific prevention strategies accordingly. While one aim of this study has achieved that breast oncologist were alerted to the high prevalence of hepatic steatosis.
It is to our knowledge the first study reporting estimates on the prevalence of MAFLD in breast cancer survivors by means of liver ultrasound elastography. We found that BCS are predisposed to HS and MAFLD than healthcare population and most of the elderly breast cancer survivors (≥60 yr) suffered HS and MAFLD, which alerts the importance of early prevention, diagnosis and treatment of HS and MAFLD in breast cancer survivors. Considering the frequency of HS and MAFLD in breast cancer survivors, liver ultrasonography screening for HS should be enhanced and further, the liver ultrasound elastography detection should be promoted and constituted into the routine screening items. Further well-designed, prospective cohort studies are required to validate our findings, and an intervention study of MAFLD development is needed to be conducted in the future.