Breast cancer is the most common malignancy in women from developed and developing countries. Detection and treatment of breast cancer in its earliest possible stage are the ultimate goal. Thus, the role of radiologists in imaging the breast is vital. At present, X-ray mammography is the “gold standard” for screening and early detection of breast cancer [8]. Women with dense breast tissue have a high risk of developing breast cancer in a ratio of 15-25% [9]. ABUS has a promising role in patients with dense breasts in detecting the hidden lesions, as it is a non-operator dependent and it needs less time of interpretation by a radiologist, helping to improve the workflow [10].
Wilczek et al. [12] stated in a study on 1668 asymptomatic women, age 40–74 years, with heterogeneously dense parenchyma (ACR C) or extremely dense breast (ACR D) that the increase in sensitivity of screening for full field digital mammography and 3D ABUS versus FFDM alone was 36.4%. The difference in specificity was − 0.7%.
Giger et al. [13] reported in a study done on 185 asymptomatic women with BI- RADS C or D breast density that the sensitivity was 57.5% for FFDM alone and 74.1% for FFDM with ABUS, yielding a statistically significant increase in sensitivity (P < 0.001) (relative increase = 29%). Overall specificity was 78.1% for FFDM alone and 76.1% for FFDM with ABUS (P = 0.496).
The Somo insight study [9] preformed on 15,318 women. The sensitivity of mammography alone was 73.2 (95% CIs 64.9, 81) versus 100% for combined ABUS and mammography. The specificity for mammography alone was 85.4 (95% CIs 84.9, 86.0) while for combined ABUS and mammography, the specificity was 72.0 (95% CIs 71.3, 72.7).
A study done on 3418 asymptomatic women with mammographically dense breasts revealed that the sensitivity and specificity of stand-alone digital mammography were 76.00% (95% CI, 54.87-90.58%) and 98.2% (95% CI, 97.76-98.59%) respectively. The positive predictive value was 20.43% (95% CI, 12.78-30.05%). The sensitivity and specificity of ABUS were 97.67% (95% CI, 87.67-99.61%) and 99.70% (95% CI, 99.46-99.86%), respectively. The positive predictive value of ABUS was 80.77% (95% CI, 67.46-90.36%) [14].
In this study, the sensitivity and specificity of stand-alone digital mammography were 53.6% (95% CI, 33.87-72.49%) and 91.7% (95% CI, 77.53-98.25%). The positive predictive value was 71.74% (95% CI, 62.75 to 79.27%).The sensitivity and specificity of ABUS were 92.8% (95% CI, 76.50 to 99.12%) and 77.78%, (95% CI, 60.85%-89.88%) respectively. The positive predictive value of ABUS was 76.47% (95% CI, 63.62 to 85.80%).
To summarize, this study showed the same results compared to the above four studies that ABUS showed an average of 30% increase in sensitivity in detecting breast malignancy in dense breast compared to digital mammography. As regards specificity, mammography had higher specificity than ABUS in all fore mentioned studies except Wilczek et al. [12], who showed near results of specificity between DM and ABUS but still higher specificity for DM.
Chen et al. [15] stated that there were no significant differences between the ABUS and HHUS in terms of sensitivity (92.5% vs. 88.0%), specificity (86.2% vs. 87.5%), accuracy (88.1% vs. 87.2%), positive predictive value (74.7% vs. 75.6%), and negative predictive value (96.3% vs. 94.3%) (P, 0.05 for all).
Choi et al. [16] evaluated a large population of asymptomatic women who were subdivided into two groups (1866 patients for ABUS and 3700 patients for HHUS) and showed that diagnostic accuracy and specificity were significantly higher for ABUS than HHUS (respectively, diagnostic accuracy 97.7 vs. 96.5% and specificity 97.8 vs. 96.7).
In this study, comparing ABUS versus HHUS as regards sensitivity (92.8% vs. 89.3%), specificity (77.8% vs. 88.9%), accuracy (82.4% vs. 89%), positive predictive value (76.5% vs. 86.2%), and negative predictive value (93.3% vs. 91.4%). In our study, ABUS had higher sensitivity (no significant difference) than HHUS, but HHUS has higher specificity and diagnostic accuracy.
Vourtsis et al. [17] performed a study that included women with breast density category C or D (aged 48.6 ± 10.8 years) were recruited. All participants underwent ABUS and HHUS examination; a subcohort of 1665 women also underwent a mammography. The overall agreement between HHUS and ABUS was 99.8%; kappa = 0.994, P < 0.0001. In this study, the overall agreement between HHUS and ABUS was kappa = 0.694, P < 0.0001, which is lower compared to the above study.
Rella et al. [18] stated that retraction phenomenon (odds ratio [OR], 76.70; 95% confidence interval [CI], 12.55, 468.70; P < 0.001) was the strongest independent predictor for malignant masses.
Chen at al [15]. stated that there were significant differences between the malignant and benign masses with respect to retraction phenomenon and hyperechoic rim in the coronal plane of the ABUS. For retraction phenomenon, both the specificity and positive predictive value of a malignant diagnosis reached 100%, and the accuracy and false-positive rate were 96.8% and 0, respectively; for the hyperechoic rim, the specificity, negative predictive value, and accuracy of a benign diagnosis were 92.8%, 95.3%, and 95.9%, respectively.
These results are going with this study that retraction phenomenon has a significant relation with malignant pathology (P value < 0.001) with 100% specficity and 75% sensitivity, while complete hyperechoic rim has significant relation with benign pathology with (P value < 0.001) with 90.5% specificity and 52.8% sensitivity.
Rella et al. [18] stated that the coronal plane also improves the evaluation of lesion margins; benign tumors are often surrounded by a continuous hyperechoic rim, while breast cancers can present a discontinuous hyperechoic rim. In this study, 14 cases showed incomplete (discontinuous) hyperechoic rim, 9 of them were benign (64%) while 5 (36%) were malignant.
Finally, Skane et al. [19] proved that combined mammography and ABUS reading by the same radiologist improved diagnostic performance and resulted in higher observer agreement. Consequently, combined reading mode should be “standard” if ABUS was implemented in screening for women with dense breasts. Prospective studies were necessary before the implementation of ABUS could be recommended in population-based screening. This study also went finally with same recommendation as mammography still could detect DCIS before IDC development as per our knowledge; further research is also recommended for this point.
The potential role of ABUS in the follow-up of benign lesions was supported by its considerable reliability in the recording of lesion location, distance from the nipple, and lesion size, these features suggested potential use in the follow-up of benign lesions as per Chang et al. [20].