The added value of S-detect in the diagnostic accuracy of breast masses by senior and junior radiologist groups: a systematic review and meta-analysis
Original Article

The added value of S-detect in the diagnostic accuracy of breast masses by senior and junior radiologist groups: a systematic review and meta-analysis

Peijun Chen1,2, Jiahui Tong1, Ting Lin1, Ying Wang3, Yuehui Yu3, Menghan Chen3, Gaoyi Yang2

1Department of Ultrasonography, The Second Clinical Medical College, Zhejiang Chinese Medicine University, Hangzhou, China; 2Department of Ultrasonography, Affiliated Hangzhou Chest Hospital, Zhejiang University School of Medicine, Chinese and Western Hospital of Zhejiang Province (Hangzhou Red Cross Hospital), Hangzhou, China; 3Department of Ultrasonography, Hangzhou Normal University Division of Health Sciences, Hangzhou, China

Contributions: (I) Conception and design: P Chen; (II) Administrative support: G Yang; (III) Provision of study materials or patients: J Tong; (IV) Collection and assembly of data: T Lin, Y Wang; (V) Data analysis and interpretation: Y Yu, M Chen; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors.

Correspondence to: Gaoyi Yang. Department of Ultrasonography, Affiliated Hangzhou Chest Hospital, Zhejiang University School of Medicine, Chinese and Western Hospital of Zhejiang Province (Hangzhou Red Cross Hospital), No. 208 Huancheng East Road, Hangzhou 310003, China. Email: yanggaoyi8@163.com.

Background: S-detect is an emerging computer-aided diagnosis (CAD) technique that provides a reference for radiologists to identify breast cancer. Some studies have shown that US (ultrasound) + S-detect can improve the diagnostic accuracy of junior radiologists more than senior radiologists, but the results are inconsistent in various studies. Therefore, this meta-analysis aimed to assess the value of S-detect combined with the US outcomes from senior and junior radiologists for the diagnosis of breast cancer.

Methods: We searched the PubMed, Cochrane Library, Embase, Web of Science, and Wanfang databases, China Biology Medicine disc, China National Knowledge Infrastructure (CNKI), and VIP database for trials on the diagnostic accuracy of US + S-detect for the diagnosis of breast masses. The search time frame was from the date of establishment of the database to August 20, 2022. Two researchers independently screened the literature, extracted the information, and evaluated the quality of the included literature using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) scale. StataSE 15.1 software was utilized to assess pooled metrics, including sensitivity, specificity, and the area under the curve (AUC).

Results: A total of 19 articles with 3,349 patients and 3,895 breast masses were included in this meta-analysis. Of these, seventeen articles evaluated the diagnostic performance of senior radiologists’ US + S-detect for breast cancer, while twelve articles reported junior radiologists’ diagnostic performance. The risk of bias was primarily attributed to patient selection, flow and timing. In the senior radiologist group, the pooled sensitivity and specificity of US + S-detect were 0.93 [95% confidence interval (CI): 0.89–0.95] and 0.86 (95% CI: 0.80–0.90), respectively, with an AUC of 0.96. As for the junior radiologist group, the pooled sensitivity and specificity of US + S-detect were 0.89 (95% CI: 0.83–0.93) and 0.79 (95% CI: 0.72–0.84), respectively, and the AUC was 0.91.

Conclusions: The results of this meta-analysis showed that the pooled sensitivity and the AUC of both the senior and junior radiologist groups were high, with good diagnostic efficacy and high clinical application. However, the results of this study are highly heterogeneous and need to be validated by collecting more high-quality studies and accumulating a larger sample size.

Keywords: S-detect; ultrasound; breast; senior radiologist; junior radiologist


Submitted Oct 18, 2022. Accepted for publication Dec 14, 2022.

doi: 10.21037/gs-22-643


Highlight box

Key findings

• The pooled sensitivity, pooled specificity, and the AUC of senior radiologists + S-detect were all higher than that of junior radiologists + S-detect.

What is known and what is new?

• A previous meta-analysis reported that the pooled sensitivity and specificity of S-detect in diagnosing breast cancer were 0.82 and 0.86

• We assessed the value of S-detect combined with the US outcomes from senior and junior radiologists for the diagnosis of breast cancer.

What is the implication, and what should change now?

• S-detect can assist radiologists to diagnose breast cancer and reduce the subjectivity between different radiologists.


Introduction

The incidence and mortality of breast cancer among women worldwide have been increasing in recent years, and in 2020, breast cancer has surpassed lung cancer as the most common cancer worldwide. Breast cancer mortality accounts for 6.9% of all tumor-related deaths (1), which seriously endangers the health of women. Early diagnosis and treatment of breast cancer are key to reducing the mortality rate and improving the survival quality of patients (2,3). Ultrasound (US) is an important imaging tool for breast cancer screening. However, the diagnostic results are easily affected by the operation and experience level of radiologists, and there is a risk of misdiagnosis and missed diagnosis (4-7).

The proposed breast imaging reporting and data system (BI-RADS) has standardized breast US examinations (8), but the influence of inter-observer variability on US diagnostic results still exists, especially in primary hospitals, due to the large number of junior radiologists, the accuracy of BI-RADS classification in the diagnosis of the nature of breast lesions and the final pathological results is low. In recent years, with the rise of artificial intelligence and the rapid development of digital healthcare, the application of computer-aided diagnosis (CAD) in medical imaging has become a research hotspot (9-11). S-detect is a CAD system based on deep learning algorithms grafted onto US instruments, which is based on the BI-RADS interpretation of the benignity and malignancy of lesions, which indicates that the breast lesion is “probably benign” or “probably malignant”. This technique can help to improve diagnostic efficiency and reduce subjective variability and has broad application prospects (12), Some studies have shown that US + S-detect can improve the diagnostic accuracy of junior radiologists more than senior radiologists, but the results are inconsistent in various studies (13,14). Because the results of previous studies were variable, there are no relevant meta-analyses examining the results of this technique in combination with senior and junior radiologists. The present meta-analysis included several domestic and international articles for quantitative synthesis, aiming to evaluate the usefulness of applying S-detect to breast US and examining whether there are differences between senior and junior radiologists, exploring how the S-detect technique can help radiologists of different levels of seniority in the clinical setting. We present the following article in accordance with the PRISMA-DTA reporting checklist (available at https://gs.amegroups.com/article/view/10.21037/gs-22-643/rc).


Methods

Data sources and search strategy

On August 20, 2022, we searched the PubMed, Cochrane Library, Embase, Web of Science, Wanfang databases, China Biology Medicine disc, China National Knowledge Infrastructure (CNKI), and VIP database for studies evaluating the accuracy of US + S-detect in breast cancer. Taking PubMed as an example, the search strategy used the following formula: “(ultrasound) AND (S-detect) AND (breast)”. Similar search formulas were used for the Cochrane Library, Embase, Web of Science, Wanfang databases, China Biology Medicine disc, China National Knowledge Infrastructure (CNKI), and VIP database.

Eligibility criteria

We relied on the population, intervention, comparison, outcome and study design principle (PICOS) to define study eligibility.

Population: patients with S-detect diagnosis of breast masses were included.

Intervention: S-detect diagnosis combined with the diagnosis of senior and junior radiologists.

Comparison: the gold diagnosis of the breast masses (final histopathological examination)

Outcome: diagnostic accuracy of breast lesions by S-detect combined with senior and junior radiologists (sensitivity, specificity, accuracy).

Study design: any type of study design, such as retrospective, prospective, or case-control, were eligible for inclusion provided the study assessed the diagnostic accuracy of breast lesions by S-detect combined with senior and junior radiologists.

Exclusion criteria: (I) case reports, conference proceedings, reviews, animal studies, etc., for which the original data were unavailable or lacking; (II) articles with small sample sizes (<20 cases); (III) articles written using the same data; and (IV) repeated articles from different databases.

Literature screening and data extraction

Two researchers (Chen PJ and Tong JH) independently completed the literature screening and data extraction. In cases of disagreement and those in which no consensus could be reached after discussion, a third researcher determined the data for inclusion. The following data were extracted from the literature: (I) basic information including the first author, year of article publication, author’s country, reference standard, study design, age of patients, number of patients and lesions, tumor diameter, type of US equipment, BI-RADS edition, radiologist’s seniority level, BI-RADS diagnostic threshold, and method of US + S-detection; and (II) 2×2 table information including true positive (TP), false positive (FP), false negative (FN), and true negative (TN). If there are multiple sets of data in one article, take the average. If the 2×2 table information was not directly obtained from the original literature, it could be calculated based on the sample size, sensitivity, and specificity provided in the article.

Assessment of study quality

The quality of the included studies was evaluated using the quality assessment of diagnostic accuracy studies-2 (QUADAS-2) scale after a thorough reading of all selected articles (15), and each of the 14 items was rated according to the actual content of each original study. Determine “yes”, “no”, “uncertain” according to the relevant signature questions included in each part, the risk of bias and applicability of the scale were assessed as “high”, “low”, or “unclear”. If the answer to the signature question is “yes”, the risk of bias is judged to be low. “No” is judged as a high risk of bias. High quality articles are randomized controlled trials (RCTs), high-quality case control or cohort studies with a very low risk of confounding or bias. The quality evaluation chart of the included literature was obtained using Review Manager 5.4 software (https://training.cochrane.org/online-learning/core-software-cochrane-reviews/revman). Quality evaluation was performed independently by two researchers; in cases of inconsistency and those in which no consensus could be reached after discussion, a third researcher made the final decision.

Statistical analysis of data

We inputted TP, FP, FN, and TN into the STATASE 15.1 software (StataCorp, College Station TX, USA) and calculated the estimated pooled sensitivity and specificity of US + S-detect for breast cancer by senior and junior radiologists, respectively. The area under the curve (AUC) was used to evaluate the diagnostic value of US + S-detect for breast cancer by radiologists of different seniority levels. The closer the AUC was to 1, the higher the diagnostic accuracy; however, the closer the AUC was to 0.5, the lower the diagnostic accuracy. Z-test was conducted to compare sensitivity, specificity, and AUC between senior and junior radiologists, and a P value ≤0.05 was considered to indicate statistical significance.

Heterogeneity analysis

Spearman’s correlation coefficient was calculated using Meta-Disc 1.4 software (https://meta-disc.software.informer.com/1.4/) to test for a threshold effect and assess whether there was heterogeneity due to a threshold effect. A threshold effect was considered to exist when Spearman’s correlation coefficient was >0 and P<0.05.

The Cochrane Q test was applied to obtain P values to quantify the heterogeneity between original studies. When the I2 value was <50%, heterogeneity was considered insignificant, and the data were directly combined for analysis. Meanwhile, when the I2 value was >50%, heterogeneity was considered significant, and a random-effects model was used to merge the data and explore the potential factors contributing to heterogeneity (16,17).

Subgroup analysis and sensitivity analysis

Subgroup analysis was performed to search for factors that might contribute to heterogeneity. The original studies were divided into two subgroups based on the possible factors, when the heterogeneity of a group decreased to <50% in subgroup analysis, it was considered that the source of heterogeneity was found through subgroup analysis. In this study, reference standard (one standard vs. two standards), number of included lesions (≥200 vs. <200), BI-RADS diagnostic threshold (BI-RADS 4a and 4b vs. BI-RADS 3 and others), the method of US + S-detect (objective binding vs. based on radiologist subjective binding or others), the methodological quality of the study (high-quality vs. acceptable-quality) were used as independent variables to delineate the subgroups, respectively.

We performed a sensitivity analysis to further explore the sources of heterogeneity and assess the reliability of the combined effect size results, and determine if there were original studies that had a large effect on heterogeneity.

Clinical application analysis

Fagan plots were created, pre-test probabilities were set, and post-test probabilities were calculated using the combined positive likelihood ratios to analyze the clinical value of using US + S-detect to diagnose breast cancer.


Results

Literature screening process

According to the formulated search strategy, eight databases were searched sequentially, and a total of 177 articles were initially obtained. After importing these articles into Endnote software (Clarivate, Philadelphia, PA, USA), 72 identical articles were excluded, and 46 articles that were deemed inconsistent based on their titles and abstracts were further checked. The remaining relevant articles were read and the inclusion and exclusion criteria were strictly implemented. Finally, a total of 19 diagnostic research articles were included in this meta-analysis (Figure 1).

Figure 1 Literature retrieval flow chart. The flow chart shows the process of selecting eligible studies and the total number (n=19) of studies included. US, ultrasound.

Basic characteristics of the included literature

This meta-analysis included 19 original studies (18-36), including eight English articles (19-26) and eleven Chinese studies (18,27-36). We extracted and summarized the basic characteristics of the included literature. Four included studies were prospective (20,21,23,26), seven were retrospective (18,19,25,29-31,33), and the remaining articles were not reported. Also, a total of 3,349 patients with 3,895 lesions were included. The average lesion diameter of the included patients was 1.10–1.93 cm, and the average age of the patients was 42.6–51.0 years. Eleven articles evaluated the diagnostic performance of US + S-detect for breast masses by both senior and junior radiologists’, six articles evaluated only senior radiologists, and two article evaluated only junior radiologists. The basic characteristics of the included literature are shown in Table 1.

Table 1

Characteristics of the included studies

First author Year Country Reference standard Study design Age (years) (mean ± SD) No. of patients No. of masses (benign/malignant) Size (cm) US equipment BI-RADS edition Seniority of doctor BI-RADS threshold Method of US + S-detect
Boyuan Xing (27) 2022 China Biopsy, excision NA 44.0±11.5 151 190 (136/54) 1.2±0.4 RS80A 5th Senior BI-RADS 4a S-detect malignant, BI-RADS upgrades, S-detect benign, BI-RADS degrades
Xin-Yi Wang (22) 2021 China Biopsy, excision NA 50.8±15.5 167 173 (95/78) 1.6±0.9 RS80A 5th Senior and junior BI-RADS 3 S-detect benign, BI-RADS 4 and 5 degrade, if not, the original BI-RADS maintain
Yongping Liang (26) 2020 China Excision Prospective 43.11±12.55 261 398 (248/150) 1.92±1.26 RS80A 5th Senior and junior BI-RADS 4a One side of S-detect malignant, BI-RADS upgrades, both sides of S-detect benign, BI-RADS degrades
Min Young Kim (21) 2021 Korea Biopsy Prospective 46±10 146 156 (146/10) 1.1±0.5 RS85 NA Senior and junior BI-RADS 3 Subjective judgment
Chenyang Zhao (25) 2020 China Biopsy, excision Retrospective 45.7 195 195 (113/82) NA RS85 NA Junior BI-RADS 3 S-detect benign, BI-RADS 4a, indicates benign, S-detect malignant, BI-RADS 3 indicates benign; others maintain original BI-RADS of doctor
Qun Xia (24) 2021 China Biopsy NA 50.9±13.9 40 40 (16/24) NA RS80A 5th Senior and junior BI-RADS 4a Subjective judgment
Qi Wei (23) 2022 China Biopsy, excision Prospective 43±12 248 266 (197/69) 1.48±0.92 RS80A 5th Senior and junior Clinical experience Subjective judgment
Eun Cho (19) 2018 Korea Biopsy, excision Retrospective 48.5±12.2 116 119 (65/54) 1.69±1.07 RS80A 5th Senior and junior BI-RADS 3 Subjective judgment
Fang He (18) 2018 China Excision Retrospective 42.6±6.2 42 54 (30/24) 1.423±0.447 RS80A NA Senior BI-RADS 4b S-detect benign, BI-RADS ≥4b indicates malignant, S-detect malignant, BI-RADS 3 indicates benign
Ji-Hye Choi (20) 2018 Korea Biopsy, 2 years of follow-up Prospective 49.5±11.8 200 200 (188/12) 1.2±0.8 RS80A NA Senior and junior BI-RADS 3 Subjective, conjunctive, disjunctive
Wenjun Xu (28) 2020 China Biopsy, excision NA 46.15±12.61 136 145 (87/58) 1.71±0.78 RS80A 5th Senior BI-RADS 4a S-detect malignant, BI-RADS upgrades, S-detect benign, BI-RADS degrades
Hong Yan (33) 2020 China Excision Retrospective 43.4±12.2 453 581 (411/170) 1.57±0.85 RS80A 5th Junior BI-RADS 4a Subjective judgment
Jiazhen Pan (32) 2021 China Excision NA 46.64±13.88 169 175 (87/88) 1.87±0.93 RS80A NA Senior and junior BI-RADS 4a S-detect malignant, BI-RADS upgrades, S-detect benign, BI-RADS degrades
Xue Ge (35) 2020 China Biopsy, excision NA 51±15 168 168 (152/16) NA SW80A NA Senior and junior BI-RADS 4b Either S-detect and BI-RADS method is malignant, then malignant, both are benign, then benign
Xiang LI (36) 2019 China Biopsy, excision NA 44.02±12.13 435 563 (403/160) 1.93±0.93 RS80A 5th Senior and junior BI-RADS 4a S-detect malignant, BI-RADS upgrades, S-detect benign, BI-RADS degrades
Yanyan Ge (34) 2020 China Biopsy, excision NA 44.2±12.0 88 98 (56/42) 1.77±1.14 RS80A NA Senior BI-RADS 4a Either S-detect and BI-RADS method is malignant, then malignant, both are benign, then benign
Feng Zhao (30) 2021 China Biopsy, excision Retrospective 44.2±12.0 120 120 (70/50) 1.25±0.53 RS80A 5th Senior BI-RADS 4a Subjective, conjunctive, disjunctive
Jinhong Wang (29) 2019 China Excision Retrospective 46.02±12.53 79 92 (59/33) 1.73±0.88 RS80A NA Senior and junior BI-RADS 4a S-detect malignant, BI-RADS upgrades, S-detect benign, BI-RADS degrades
Lan Shen (31) 2022 China Excision Retrospective 42.69±12.34 135 162 (107/55) 1.87±0.51 RS80A 5th Senior NA Either S-detect and BI-RADS method is malignant, then malignant, both are benign, then benign

US, ultrasound; BI-RADS, breast imaging reporting and data system; NA, not available.

Methodologic quality evaluation

Review Manager 5.4 software (https://training.cochrane.org/online-learning/core-software-cochrane-reviews/revman) was used to evaluate the quality of the included original studies according to the QUADAS-2 scale. The risk of bias was primarily attributed to patient selection and flow and timing. The risk of bias from the index test was low, as was the risk of bias from the reference standard. Figure 2 displays the quality evaluation of the included literature.

Figure 2 Methodological quality graphs (risk of bias and applicability concerns) of the included studies as percentages.

Threshold effect

The 2×2 table data (TP, FP, FN, TN) from nine studies of US + S-detect in the senior radiologist group were imported into the Meta Disc 1.4 statistical software for analysis, yielding a Spearman correlation coefficient of −0.213 (P=0.411). The Spearman correlation coefficient from seven studies of US + S-detect in the junior radiologist group was 0.280 (P=0.379), indicating that there was no threshold effect in either group.

Diagnostic performance of the combination of S-detect with senior radiologists

Seventeen of the studies (involving 3,119 lesions) reported on the diagnostic performance of the combination of S-detect with senior radiologists in differentiating benign from malignant breast masses. Combining S-detect with senior radiologists, the pooled sensitivity was 0.93 [95% confidence interval (CI): 0.89–0.95, I2=64.74%] and the pooled specificity was 0.86 (95% CI: 0.80–0.90, I2=86.11%). Figure 3A shows the Forest plot of the sensitivity and specificity. The AUC of the summary receiver operating characteristic (SROC) curve was 0.96 (95% CI: 0.93–0.97) (Figure 3B).

Figure 3 (A) Forest plot of the sensitivity and specificity of US + S-detect for identifying breast cancer in the senior radiologists group. (B) SROC curve of US + S-detect for identifying breast cancer in the senior radiologist’s group. SENS, sensitivity; SPEC, specificity; SROC, summary receiver operating characteristic; AUC, the area under the curve; US, ultrasound.

Diagnostic performance of the combination of S-detect with junior radiologists

Twelve of the studies (involving 2,953 lesions) reported on the performance of the combination of S-detect with junior radiologists in diagnosing breast cancer. By combining S-detect with junior radiologists, the pooled sensitivity was 0.89 (95% CI: 0.83–0.93, I2=74.48%), the pooled specificity was 0.79 (95% CI: 0.72–0.84, I2=92.94%) (Figure 4A), and the AUC of the SROC curve was 0.91 (95% CI: 0.88–0.93) (Figure 4B).

Figure 4 (A) Forest plot of the sensitivity and specificity of US + S-detect for identifying breast cancer in the junior radiologists group. (B) SROC of US + S-detect for identifying breast cancer in the junior group. SENS, sensitivity; SPEC, specificity; SROC, summary receiver operating characteristic; AUC, the area under the curve; US, ultrasound.

Comparison of diagnostic accuracy between the combination of S-detect with senior radiologists and the combination of S-detect with junior radiologists

Combining S-detect with senior radiologists, the pooled sensitivity, pooled specificity, and the AUC in differentiating benign from malignant breast masses were 0.93, 0.86 and 0.96. The pooled sensitivity, pooled specificity, and the AUC of junior radiologists were 0.89, 0.79 and 0.91. The pooled sensitivity, pooled specificity, and the AUC of senior radiologists plus S-detect were all higher than that of junior radiologists plus S-detect. There is significant difference in the AUC (P<0.01), however, there were without significant difference in the pooled sensitivity (P=0.188) and pooled specificity (P=0.086).

Heterogeneity detection

Subgroup analysis

To identify the potential factors contributing to heterogeneity, the original studies were divided into subgroups according to reference standard, number of included lesions, BI-RADS diagnostic threshold, the method of US + S-detect and the methodological quality of the study for subgroup analysis of the included literature in the senior and junior radiologist groups, respectively. The subgroup analysis results are shown in Table 2 and Table 3.

Table 2

Subgroup analysis of the diagnostic performance of US + S-detect in the senior radiologist group

Covariate/subgroup Studies, n Sensitivity (95% CI) I2 Specificity (95% CI) I2
Reference test
   One method 7 0.95 (0.89–0.98) 73.21 0.85 (0.76–0.91) 84.51
   Two methods 10 0.91 (0.87–0.94) 58.69 0.86 (0.79–0.91) 88.00
No. of lesion
   ≥200 4 0.95 (0.89–0.98) 83.24 0.84 (0.78–0.89) 83.63
   <200 13 0.92 (0.88–0.94) 52.94 0.87 (0.80–0.91) 88.93
BI-RADS diagnostic cut-offs
   BI-RADS 4a and 4b 11 0.93 (0.89–0.96) 73.46 0.87 (0.81–0.91) 76.90
   BI-RADS 3 and others 6 0.92 (0.86–0.95) 33.37 0.83 (0.72–0.90) 90.35
US combined with the S-detect method
   Objective 12 0.94 (0.91–0.97) 66.63 0.87 (0.80–0.92) 87.34
   Subjective and others 5 0.84 (0.78–0.89) 0 1.83 (0.75–0.89) 86.40
The methodological quality of the study
   High-quality 6 0.96 (0.90–0.98) 74.08 0.85 (0.77–0.90) 88.11
   Acceptable-quality 11 0.91 (0.87–0.94) 45.62 0.85 (0.78–0.90) 85.09

US, ultrasound; BI-RADS, breast imaging reporting and data system.

Table 3

Subgroup analysis of the diagnostic performance of US + S-detect in the junior radiologist group

Covariate/subgroup Studies, n Sensitivity (95% CI) I2 Specificity (95% CI) I2
Reference test
   One method 6 0.90 (0.84–0.94) 57.31 0.76 (0.63–0.85) 93.86
   Two methods 6 0.86 (0.77–0.92) 76.41 0.82 (0.74–0.88) 90.42
No. of lesion
   ≥200 5 0.87 (0.78–0.92) 86.80 0.83 (0.78–0.87) 82.43
   <200 7 0.90 (0.83–0.94) 44.67 0.75 (0.63–0.84) 92.87
BI-RADS diagnostic cut-offs
   BI-RADS 4a and 4b 7 0.88 (0.81–0.92) 82.17 0.69 (0.56–0.82) 65.06
   BI-RADS 3 and others 5 0.91 (0.83–0.95) 54.43 0.75 (0.58–0.87) 95.74
US combined with S-detect method
   Objective 7 0.90 (0.82–0.95) 86.31 0.78 (0.67–0.86) 95.99
   Subjective and others 5 0.86 (0.80–0.90) 0 1.78 (0.64–0.88) 96.14
The methodological quality of the study
   High-quality 7 0.91 (0.83–0.96) 85.80 0.90 (0.82–0.95) 95.99
   Acceptable-quality 5 0.84 (0.78–0.88) 0 0.79 (0.74–0.84) 58.12

US, ultrasound; BI-RADS, breast imaging reporting and data system.

In the senior radiologist group, the heterogeneity for sensitivity of the BI-RADS 3 and others group, the subjective and others group, and acceptable-quality group were reduced to 50%, indicating that these three factors were among the sources of heterogeneity of sensitivity in the original study. In the junior radiologist group, the heterogeneity for sensitivity of the No. of lesion <200, subjective and others, and acceptable-quality subgroups were reduced to 50%, indicating that these three factors were a source of heterogeneity of sensitivity in the original study.

Sensitivity analysis

Sensitivity analyses were conducted separately for the senior and junior radiologist groups. After included literature were removed successively, the remaining literature was combined to calculate the value of I2 for sensitivity analysis. and no significant effect of the literature on the results was found, indicating that the results of this meta-analysis are stable.

Clinical value analysis

Fagan diagrams were constructed (Figure 5), assuming a pre-test probability of 50%, and post-test probabilities of 87% and 81% were obtained after calculation for the senior and junior radiologist groups, respectively. This indicated that the application of US + S-detect has a high clinical application for the diagnosis of breast cancer.

Figure 5 Fagan diagrams of US + S-detect for the diagnosis of breast cancer. (A) Senior radiologists group. (B) Junior radiologists group. LR, likelihood ratio; US, ultrasound.

Discussion

US is widely used for the diagnosis of breast lesions, but it is influenced by the subjective factors of the operator. Furthermore, it has been reported that when using the BI-RADS vocabulary for the assessment of breast masses, the specificity of less experienced radiologists is significantly lower than that of experienced radiologists (37). With the development of medical imaging technology, the feasibility of artificial intelligence technology applied to the diagnosis of breast diseases has been reported by several articles. S-detect reduces the influence of the subjective factors of radiologists to a certain extent, making the results more objective (38). In this meta-analysis, we collected domestic and international articles on the combined diagnosis of US + S-detect by senior and junior radiologists to investigate whether the combination of both could improve the discrimination of benign and malignant breast masses.

A previous meta-analysis (39) reported that the pooled sensitivity and specificity of S-detect in diagnosing breast cancer were 0.82 and 0.86, respectively, and could be a complement to conventional US. In our meta-analysis, we selected 19 articles in which US + S-detect were combined to diagnose breast masses; seventeen of these articles evaluated the diagnostic performance of US + S-detect for breast cancer by senior radiologists and twelve articles evaluated the diagnostic performance of US + S-detect for breast cancer by junior radiologists. The diagnostic indexes of US + S-detect by senior and junior radiologists were respectively calculated and quantitatively pooled by meta-analysis. The literature included in both groups had no threshold effect, but the heterogeneity was significant, so a random-effects model was used for the combined analysis of data. The results showed that in the senior radiologist group, the pooled sensitivity, specificity, and AUC of US + S-detect were 0.93 (95% CI: 0.89–0.95), 0.86 (95% CI: 0.80–0.90), and 0.96 (95% CI: 0.93–0.97). In the junior radiologist group, pooled sensitivity, pooled specificity, and AUC of US + S-detect were 0.89 (95% CI: 0.83–0.93), 0.79 (95% CI: 0.72–0.84) and 0.91 (95% CI: 0.88–0.93).

It was suggested that the diagnostic performance was high in both groups; pooled sensitivity, the pooled specificity and AUC were all higher in the senior radiologist group than in the junior radiologist group, and the AUC value was significantly different between the two groups (P<0.01). Some articles showed that the improvement was more significant in the junior radiologist group compared to US (19-21,23). Meanwhile, we analyzed the clinical application value of US + S-detect by plotting Fagan diagrams, setting the pre-test probability at 50% and the post-test probability at 87% and 81% for the senior and junior groups, respectively. The pre-test probability refers to the prevalence rate estimated by the clinician based on the patient’s medical history, signs, and personal experience before the patient undergoes this test. The more the post-test probability increases compared to the pre-test probability, the more valuable the test is in terms of clinical application. Therefore, the US + S-detect is of high clinical value for the diagnosis of breast cancer by both senior and junior radiologists.

The malignancy rate of breast masses classified as BI-RADS 4a is approximately 2–10%, and most category 4a breast masses, although benign, may be subject to unnecessary biopsy (40,41). A previous meta-analysis by Park et al. (42) reported that downgrading of BI-RADS category 4a breast masses to BI-RADS category 3 when US elastography was combined with US for diagnosis reduced unnecessary biopsies in 41.1% of breast category 4a nodules. Combining S-detect can also reduce the biopsy rate by downgrading BI-RADS 4a masses. Combining S-detect to diagnose breast masses reduced the rate of unnecessary biopsies (22,23,25), but downgrading can also result in false-negative results for malignant nodes, so further training in S-detect and the empirical judgment of radiologists is also important.

Since the results of the heterogeneity test showed that the I2 values of sensitivity and specificity were >50% for both the senior and junior radiologist groups, indicating a pronounced heterogeneity between the original studies, the causes of heterogeneity need to be explored. The results of the subgroup analysis to determine the factors that may lead to heterogeneity. It showed that the heterogeneity for sensitivity of the BI-RADS diagnostic cut-offs, US combined with the S-detect method, and the methodological quality of the study may lead to the sources of heterogeneity of sensitivity in the senior radiologist groups. In the junior radiologist group, The No. of lesion, US combined with the S-detect method, and the methodological quality of the study indicated that these three factors may be a source of heterogeneity of sensitivity in the original study. The sources of heterogeneity were further explored by sensitivity analysis, and no significant effect of the literature on the results was observed, indicating good stability of the meta-analysis.

Limitations of this meta-analysis: (I) the study populations of most of the original studies were Chinese patients, leading to the possibility of geographical bias, and thus, more high-quality studies from other countries should be included in future studies to further validate the reliability of the diagnostic results. (II) There was a high degree of heterogeneity in the included literature, and some of the original studies included cases from a retrospective study method; therefore, more high-quality prospective multicenter studies are needed to further explore the diagnostic efficacy of US + S-detect for breast cancer in-depth.


Conclusions

In this study, we collected diagnostic studies from domestic and foreign countries for meta-analysis to evaluate the diagnostic performance of US + S-detect for breast cancer by radiologists of different seniority levels. The combined results showed that the sensitivity and the AUC were all high in the senior and junior radiologist groups, which have a high clinical application value. However, the results of this study are somewhat heterogeneous, and thus, it is still necessary to collect more articles and accumulate a larger sample size for validation.


Acknowledgments

Funding: This work was supported by the Agriculture and Social development plan of Hangzhou (grant No. 20190101A09).


Footnote

Reporting Checklist: The authors have completed the PRISMA-DTA reporting checklist. Available at https://gs.amegroups.com/article/view/10.21037/gs-22-643/rc

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://gs.amegroups.com/article/view/10.21037/gs-22-643/coif). The authors have no conflicts of interest to declare.

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(English Language Editor: A. Kassem)

Cite this article as: Chen P, Tong J, Lin T, Wang Y, Yu Y, Chen M, Yang G. The added value of S-detect in the diagnostic accuracy of breast masses by senior and junior radiologist groups: a systematic review and meta-analysis. Gland Surg 2022;11(12):1946-1960. doi: 10.21037/gs-22-643

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