Patient’s demographic data
This prospective study was performed on 110 female patients with history of breast cancer and underwent operation either conservative breast surgery (86 patients) (78.2%) or modified radical mastectomy (MRM) (24 patients) (21.8%). Their age ranged from 34 to 60 years with a mean ± SD = 47.23 ± 7.10. It was performed during the period from January 2018 till December 2019 and was approved by our institution’s ethics committee. All patients gave their informed consent before inclusion in the study.
Inclusion criteria
Female patients with history of breast cancer and underwent surgery for treatment of breast cancer and referred for MRI with suspicion to have local regional recurrence on the basis of clinical examinations (e.g., palpable mass or an irregular area of firmness at the operative bed, skin changes, skin inflammation or area of redness, one or more painless nodules on or under the skin of the chest wall in cases of MRM, or thickening along or near the mastectomy scar) or on the basis of sonomammographic examination (e.g., areas of parenchymal distortion, irregular shaped masses with skin retraction, and hypoechoic masses with posterior shadowing).
Exclusion criteria
Patients who have contraindications to do MRI as patients with cardiac pace maker, patients with cochlear implant and ocular foreign body, patients on neoadjuvant chemotherapy, and patients who performed unplanned excision of breast cancer.
MRI technique
MRI was performed on 1.5 T MR imaging unit (Philips Ingenia). All patients were examined in the prone position using dedicated breast coil. All patients underwent the following: FSE axial non-fat saturated TIWI (TR 450 ms and TE 14 ms), axial non-fat-suppressed T2-weighted turbo spin-echo (TR 4500 ms and TE 97 ms), and axial STIR images (TR 7000–9000 ms, TE 70 ms, and inversion time (TI) was 150 ms).
DWI was obtained before contrast medium injection using a multislice, single-shot, spin-echo, echo-planar image sequence. A set of multiple axial scans of the breast was obtained. The scanning parameters were TR/TE = 10.000:108 ms, NEX = 8–16, bandwidth = 300 kHz, FOV = 300–360 mm, slice thickness was 4 mm, and acquisition matrix = 256 × 128. The diffusion gradients were applied in three orthogonal directions (x, y, and z). Diffusion-weighted MR images were acquired with b factor of 0 or 500 and 1000 s/mm2, and ADC maps were reconstructed.
DCE-MRI was performed after injection of a bolus of gadopentetate dimeglumine, in a dose of 0.2 m-mol/kg using an automated injector at a rate of 3–5 ml/s. This was followed by a bolus injection of saline (a total of 20 ml at 3–5 ml/s). Dynamic images were obtained in the axial plane with fat suppression. The sequence used was FLASH 3-D GRE-T1WI with the following parameters: TR 4–8 ms, TE 2 ms, flip angle 20–25, slice thickness 2 mm with no inter-slice gap, FOV 300–360 mm, and the matrix was 307 × 512. Dynamic study consists of one pre-contrast and 5 postcontrast series. Subtraction images were obtained by subtracting each of the pre-contrast images from each post-contrast series images.
Image interpretation
Two experienced radiologists blinded to each other and blinded to the results of histopathological examinations evaluated the MRI images for the following:
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1)
Signal intensity of the lesion on non-contrast images (T1WI, T2WI, and STIR).
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2)
As regard to diffusion images, there were two methods for evaluation: (A) qualitative analysis of DWI was performed by a combined visual assessment of the high b value DWI (b 1000) and the corresponding ADC maps. Recurrent breast carcinoma appeared high SI on the high b value DWI and of low SI on ADC maps. Benign post-operative breast lesions (post-operative scar, fat necrosis, and post-operative seroma) are characterized by low SI on high the b value DWI and high SI on ADC map. Sometimes, post-operative seroma appeared of high SI on both DWI and ADC map, and this is termed T2 shine through artifact (decreased on high b value image). (B) Quantitative analysis of DWI was performed by calculating the ADC values of tissues. An ROI is manually drawn along the margins of the lesion on ADC map images.
On the basis of non-contrast MR images and diffusion images, recurrent breast carcinoma was diagnosed when the lesion appeared of low signal intensity on T2WI, low signal intensity on T1WI, and show restricted diffusion with low ADC value (Fig. 1). Post-operative fat necrosis was diagnosed when the lesion showed fat signal intensity (high signal intensity on T1WI and low signal intensity on STIR images compared with the surrounding breast fat) and appeared free on diffusion with high ADC value (Fig. 2). Post-operative seroma was diagnosed when the lesion appeared of high signal intensity on T2WI and STIR images, low signal intensity on T1WI, and appeared free on diffusion with high ADC value (Fig. 3). Post-operative scar was diagnosed when the lesion appeared of intermediate signal intensity on T2WI, low signal intensity on T1WI, and free on diffusion with high ADC value (Fig. 4). We did not depend on the assessment of lesion shape and margins to differentiate between benign post-operative changes and recurrent breast carcinoma as post-operative scar, and fat necrosis usually has irregular shape and margins so could not be discriminated from recurrent breast carcinoma on the basis of lesion shape and margins.
Final diagnosis
The results of histopathological examinations were considered as our standard of reference. The interval between the MRI examination and the histopathological examination was 10–15 days. When patients were suspected to have recurrent breast carcinoma, post-operative scar or fat necrosis on the basis of MRI, Tru-cut biopsy was done using 14–16 gauge core needle. When patients were suspected to have post-operative seroma on the basis of MRI, FNAC was performed to exclude presence of malignant cells.
Statistical analysis
Data was analyzed using the Statistical Package for Social Science software computer program version 23 (SPSS, Inc., Chicago, IL, USA). Data were expressed as mean ± SD (standard deviation) for quantitative parametric data and as frequency (number-percent) for qualitative data. Kappa agreement was used for inter-rater agreement. The intraclass correlation coefficient (ICC) was used as a measure of inter-rater agreement for continuous scales. Sensitivity, specificity, PPV (positive predictive value), NPV (negative predictive value), and accuracy were calculated to differentiate between benign post-operative lesions and recurrent breast carcinoma by unenhanced MRI. The sensitivity and specificity of ADC to differentiate between benign and malignant lesions were examined at different cutoff points using ROC curve analysis to determine the best cutoff point as well as the diagnostic power of each test. P value less than 0.05 was considered statistically significant.