Breast MRI has been shown to be the most sensitive tool for the detection of breast cancer (4-7). Previous studies revealed that breast MRI is a reliable imaging modality for predicting tumor extension and for the detection of additional ipsilateral and contralateral tumor foci (15, 16). Exact treatment planning and accurate tumor removal is of the utmost importance (7).
Recently, breast-conserving surgery (BCS) for early breast cancer has proven to be as effective as conventional mastectomy in terms of the long-term survival rate and the recurrence rate (1-3). In addition, BCS is more esthetic than conventional mastectomy. Because the relative contraindications of BCS include multifocal malignancies and large tumor size, a precise preoperative evaluation of breast cancer, such as the extent of the disease and the existence of multifocal or multicentric disease, is needed for performing BCS (17).
The preoperative breast MRI has been shown to be the most sensitive tool for detecting breast cancers, but this technique has some shortcomings, such as false positive findings, possible over diagnosis, and unnecessary resections (7). National and international guidelines and the European society of breast cancer specialists (EUSOMA) recommended the use of preoperative breast MRI for selected patients with multifocal disease, lobular carcinoma, high parenchymal density, extensive DCIS, and occult primary tumor (7, 18-20). In the recent reports, they stated that the use of preoperative breast MRI should be selective and only used in patients with a maximum likelihood of additional information (7, 9, 10). In a report to reveal a better selection of patients who should undergo preoperative breast MRI, they recommended that premenopausal state, lobular carcinoma, and high parenchymal density should be embedded in clearly defined guidelines for the use of preoperative breast MRI in patients with known breast cancer (7). In our study, the overall cancer detection sensitivity of mammography was 47.4%; 60% in fatty breast and 42.9% in dense breast. The cancer detection sensitivities of HHUS and ABVS scanning without knowledge of MRI were 65.8%, and 64.5%, respectively. Especially in patients with small-sized lesions and DCIS, ultrasound without knowledge of MRI showed a lower detection rate than ultrasound with knowledge of MRI (P value < 0.05). With knowledge of MRI, HHUS and ABVS detected most lesions, irrespective of size and DCIS. Although we only enrolled breast cancer patients who underwent HHUS and ABVS for newly detected lesions found via preoperative breast MRI, this result shows that other conventional image modalities can not replace the preoperative MRI.
Table 2.
Cancer Detection Accuracy (N = 120 Lesions)
Variables | Sensitivity | Specificity | PPV | NPV |
---|
Pre-MRI (without MRI) | | | | |
MMG (categorya) | 47.4 | 93.2 | 92.3 | 50.6 |
Fatty breast (1 + 2) | 60.0 | 90.5 | 85.7 | 70.4 |
Dense breast (3 + 4) | 42.9 | 95.7 | 96.0 | 40.7 |
1st HHUS detectionb | 65.8 | 59.1 | 73.5 | 50.0 |
ABVS detectionb | 64.5 | 68.2 | 77.8 | 52.6 |
Conjunctiveccombination detection | 67.1 | 56.8 | 72.9 | 50.0 |
Disjunctived combination detection | 63.2 | 75.0 | 81.4 | 54.1 |
1st HHUS categorya (n = 68) | 56.6 | 100.0 | 100.0 | 57.1 |
ABVS categorya (n = 63) | 59.2 | 97.7 | 97.8 | 58.1 |
Post-MRI (with MRI) | | | | |
1st + 2nd HHUS detectionb | 94.7 | 13.6 | 65.5 | 60.0 |
ABVS detectionb | 98.7 | 6.8 | 64.7 | 75.0 |
Conjunctiveccombination | 100.0 | 6.8 | 65.0 | 100.0 |
Disjunctived combination | 93.4 | 13.6 | 65.1 | 54.6 |
Abbreviations: ABVS, automated breast volume scanner; HHUS, handheld ultrasound; MMG, mammography; NPV, negative predictive value; PPV, positive predictive value.
aCategory: category 1, 2, and 3 were defined as negative category (-), 4, 5, and 0 were defined as positive category (+) given to MMG, 1st HHUS category, ABVS category, and MRI.
bDetection: non-detection was defined as negative (-), detection was defined as positive (+) given to HHUS, ABVS, conjunctive and disjunctive combination detections.
cConjunctive combination: non-detection; non-detection on both the 2nd HHUS and ABVS scans; detection; detection on either the 2nd HHUS or ABVS scans.
dDisjunctive combination: non-detection; non-detection on either the 2nd HHUS or ABVS scans; detection; detection on the both the 2nd HHUS and ABVS scans.
With knowledge of MRI, all modalities showed extremely low specificity because the analyzed lesions were already suspicious on MRI. Based on the known fact that the specificity for breast MRI is variable, our result showing low specificity on ultrasonography (USG) has a different meaning from the specificity of ultrasound alone. In this study, the breast cancer patients who had newly been detected with an additional suspicious lesion on MRI (above BI-RADS category 4 and BI-RADS category 6 [known cancer] were enrolled. The patients who had proven cancer(s) with/without non-suspicious lesions on MRI (BI-RADS category 6) were not included. MRI had high sensitivity and found a lot of suspicious looking lesions later proven benign and borderline lesions. With knowledge of MRI, the rates of non-detected lesion on ABVS and HHUS were very low. So, the specificities of HHUS and ABVS with knowledge of MRI could be low. The detection sensitivity of ultrasound on the MRI-detected lesions had the most significant value. In addition, because of the suspiciously malignant findings on the MRI image, MRI-detected lesions were not evaluated by BI-RADS ultrasound categories.
Nevertheless, if a suspicious finding on an MRI image is found, a subsequent biopsy should be performed for preoperative staging; however, MRI-guided biopsy is expensive, time-consuming, and uncomfortable for the patient (11). Targeted ultrasound may visualize and further characterize these lesions and facilitate ultrasound-guided biopsy when correlated with MRI findings (21). Therefore, when abnormalities detected by MRI lack visualization on conventional imaging (mammograms or first breast ultrasound), a targeted or MRI-directed ultrasound is commonly performed to further characterize the MRI findings (22).
The role of targeted ultrasound has been investigated by several authors (11, 21, 23-29). Previous studies showed that the frequency of which MRI-detected lesions are found by ultrasound ranges from 23% to 89%. The mean detection rate of ultrasound was 63%. Carbognin et al. documented that more than 90% of lesions > 10 mm were detected on ultrasound when compared with lesions that were 10 mm or less. Wiratkapun et al. reported a statistically significant direct association between increasing MRI mass lesion size and the ultrasound detection rate (odds ratio = 1.23). In this study, ultrasound without knowledge of MRI showed a lower detection rate for small-sized lesions (P value < 0.05). However, ultrasound with knowledge of MRI showed no significant association between the detection rate and lesion size.
Table 3.
Characteristics of the Detected Lesion Using HHUS, ABVS and Their Combination Between Pre-MRI and Post-MRIa,b
| Pre-MRI (Without MRI) | Post-MRI (with MRI) |
---|
| MMG | P value | 1st HHUS | P value | ABVS | P value | 1st and 2nd HHUS | P value | ABVS | P value | Conjunctive | P value | Disjunctive | P value |
---|
| (-) | (+) | | (-) | (+) | | (-) | (+) | | (-) | (+) | | (-) | (+) | | (-) | (+) | | (-) | (+) | |
---|
Detection | 81 (67.5) | 39 (32.5) | | 52 (43.3) | 68 (56.7) | | 57 (47.5) | 63 (52.5) | | 10 (8.3) | 110 (91.7) | | 4 (3.3) | 116 (96.7) | | 3 (2.5) | 117 (97.5) | | 11 (9.2) | 109 (90.8) | |
Pathology | | | < 0.0001 | | | 0.0261 | | | 0.0022 | | | 0.0941 | | | 0.1515 | | | 0.0569 | | | 0.1455 |
1- Benign | 33 (40.7) | 2 (5.1) | | 20 (38.5) | 15 (22.1) | | 24 (42.1) | 11 (17.5) | | 6 (60.0) | 29 (26.4) | | 3 (75.0) | 32 (27.6) | | 3 (100.0) | 32 (27.4) | | 6 (54.6) | 29 (26.6) | |
2- Borderline | 8 (9.9) | 1 (2.6) | | 6 (11.5) | 3 (4.4) | | 6 (10.5) | 3 (4.8) | | 0 (0.0) | 9 (8.2) | | 0 (0.0) | 9 (7.8) | | 0 (0.0) | 9 (7.7) | | 0 (0.0) | 9 (8.3) | |
3- Malignancy | 40 (49.4) | 36 (92.3) | | 26 (50.0) | 50 (73.5) | | 27 (47.4) | 49 (77.8) | | 4 (40.0) | 72 (65.5) | | 1 (25.0) | 75 (64.7) | | 0 (0.0) | 76 (65.0) | | 5 (45.5) | 71 (65.1) | |
Lesion type in MRI | | | 0.9285 | | | 0.1597 | | | 0.1456 | | | 0.0145 | | | 0.0168 | | | 0.0788 | | | 0.0037 |
1- mass | 67 (82.7) | 32 (82.1) | | 40 (76.9) | 59 (86.8) | | 44 (77.2) | 55 (87.3) | | 5 (50.0) | 94 (85.5) | | 1 (25.0) | 98 (84.5) | | 1 (33.3) | 98 (83.8) | | 5 (45.5) | 94 (86.2) | |
2- non-mass | 14 (17.3) | 7 (18.0) | | 12 (23.1) | 9 (13.2) | | 13 (22.8) | 8 (12.7) | | 5 (50.0) | 16 (14.6) | | 3 (75.0) | 18 (15.5) | | 2 (66.7) | 19 (16.2) | | 6 (54.6) | 15 (13.8) | |
Lesion size in MRI, | 1.2 ± 1.5 | 2.3 ± 1.7 | < 0.0001 | 1.3 ± 1.6 | 1.8 ± 1.6 | 0.0053 | 1.2 ± 1.6 | 1.9 ± 1.6 | 0.0002 | 1.5 ± 1.3 | 1.6 ± 1.7 | 0.8640 | 2.0 ± 1.4 | 1.6 ± 1.7 | 0.3676 | 2.2 ± 1.6 | 1.6 ± 1.6 | 0.3811 | 1.5 ± 1.2 | 1.6 ± 1.7 | 0.8021 |
Cancer type | | | 0.0590 | | | < 0.0001 | | | < 0.0001 | | | 0.3652 | | | 0.1053 | | | - | | | 0.0831 |
Invasive cancersc | 33 (82.5) | 35 (97.2) | | 18 (69.2) | 50 (100) | | 19 (70.4) | 49 (100.0) | | 3 (75.0) | 65 (90.3) | | 0 (0.0) | 68 (90.7) | | 0 (0.0) | 68 (89.5) | | 3 (60.0) | 65 (91.6) | |
DCIS | 7 (17.5) | 1 (2.8) | | 8 (30.8) | 0 (0.0) | | 8 (23.6) | 0 (0.0) | | 1 (25.0) | 7 (9.7) | | 1 (100.0) | 7 (9.3) | | 0 (0.0) | 8 (10.5) | | 2 (40.0) | 6 (8.5) | |
Abbreviations: ABVS, automated breast volume scanner; DCIS, ductal carcinoma in situ; HHUS, handheld ultrasound; MMG, mammography.
aValues are expressed as No. (%) or mean ± SD.
bStatistics were carried out using Chi-square test, Fisher’s exact test and Wilcoxon rank sum test.
cInvasive cancer: invasive ductal cancer, invasive micropapillary cancer, mucinous cancer, and invasive lobular cancers
In this study, the detection rate using ABVS was higher than that using HHUS (98.7% vs. 94.7%, P < 0.05) with knowledge of MRI, demonstrating the advantage of ABVS over HHUS scanning for standardized, reproducible, and bilateral whole-breast imaging. In contrast to HHUS, which is a real-time examination, the reader can review the whole images scanned by ABVS reproducibly. This advantage could reduce the number of missed diagnoses. The ABVS also provides a more accurate view than HHUS for evaluating breast masses because each cross-sectional plane of the scanned images can be visualized. The ability to scan a 3D volume of both breasts allows the images to be reviewed irrespectively of the location and time of the actual examination. These characteristics make the ABVS a promising diagnostic tool for targeted ultrasound. Additionally, the size of the lesions on MRI correlated more with those detected using ABVS than HHUS.
However, the utility of real-time imaging by HHUS to determine the mobility of the lesion is an important feature that is not available with the ABVS. Moreover, detection on HHUS is needed for an ultrasound-guided biopsy. If the initial ultrasound was performed by ABVS and a targeted ultrasound is necessary, a re-review of the ABVS images could be useful without requiring the patient to return for a targeted HHUS examination. In conjunctive combination of HHUS and ABVS techniques, the detection sensitivities were improved in both cases with and without knowledge of MRI. In disjunctive combination of HHUS and ABVS techniques, the specificities were improved with and without knowledge of MRI.
Our study was limited by the small study population size. Furthermore, we only enrolled lesions detected on MRI so we could not judge other lesions that might be missed in MRI. However, to our knowledge, this report was the first study to analyze the clinical utility, which includes detection rate and diagnostic accuracy of the combined use of ABVS and HHUS for MRI-detected lesions.
With knowledge of MRI, HHUS and ABVS imaging detected most lesions and the conjunctive combination of HHUS and ABVS showed the highest sensitivity. The sensitivity of ABVS was higher than HHUS, and the size of the lesions on MRI correlated more with those detected using ABVS than HHUS. Therefore, after preoperative MRI, ABVS imaging could be suggested for optimally targeted ultrasound methods. Then, the HHUS technique could be selected for ultrasound-guided biopsy or additional targeted methods.
In conclusion, the role of MRI for preoperative assessment is irreplaceable. With knowledge of MRI, the conjunctive combination of HHUS and ABVS techniques showed the highest sensitivity. In additional, ABVS imaging is better for preoperative evaluation than HHUS.
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