Breast imaging: newer developments

 Mammography is a medical imaging study that uses low dose x-rays to examine the human breast.  It can detect tumors before they are felt on physical examinationand can find microcalcifications that may indicate breast cancer.  Recently digital imaging has replaced film/screen mammography as it provides better image quality and allows easier storage and image sharing. Three dimensional mammography known as tomosynthesis is a newer mamographic technique which is useful in women with dense breast parenchyma.  Multiple randomized studies have demonstrated decreases in mortality from breast cancer by approximately 30% when screening mammograms are performed annually in women whose age is between 40 to 70. 

In 1990, Jackson in a Radiology article suggested ultrasound as a valuable tool in breast imaging especially when a mass is felt clinically or detected on mammography. Ultrasound helps in differentiating between solid masses that can be cancerous and fluid filled cysts that are benign.  In cases when a cancer is suspected ultrasound is used to guide needle biopsies and other therapeutic procedures such as breast cancer ablation. While useful, ultrasound is not a replacement for mammography.  For women with dense breasts when combined with mammography and clinical examination they provide a comprehensive evaluation.

In 1976, Frank, Ferris et al in a NEJM article described the technique of needle localization that allows placement of a wire with its tip adjacent to the lesion.  The technique ensures tat the surgeon can remove the suspicious finding with minimal tissue removal.  Wire localization can be performed either under mammographic or ultrasound guidance.

Magnetic resonance imaging (MRI) is using a magnetic field and radio waves to create detailed images of the breast.  Research in breast MRI started in 1980 in the USA and Germany.  MRI is highly sensitive and can detect abnormalities not seeing in either mammography or ultrasound.  In 1986, Heywang et al demonstrated that breast cancers enhance following gadolinium administration. In 1990, Kuhl et al published their study in the use of MRI in the screening of women at high risk for breast cancer, such as those with strong family history or genetic mutations like BRCA1 or BRCA2.

This post is dedicated to my friend and associate John Olsen MD who introduced the concept of mobile mammography and was the first who did stereotactic biopsies at Ohio State University.  He was the chief of Nuclear Medicine and Breast imaging at OSU and President of our departmental corporation URI.  I had the pleasure working with him during my tenure at OSU and learning from him on how to allay cancer patients fears.

Breast MRI Improves depiction of DCIS Components

A study by Kuhl et al published in Radiology found magnetic resonance imaging (MRI) of the breast improves depiction of ductal carcinoma in situ (DCIS) components of invasive breast cancers prior to surgery.

The authors performed a prospective two-center study of 593 patients with biopsy proven invasive breast cancer that underwent breast MRI in addition to conventional imaging. 

The outcomes showed surgical-pathologic evaluation demonstrated DCIS components in 139 (23%) women. MRI had significantly higher sensitivity in the diagnosis of DCIS components pre-operatively in (84%; 118 women out of 139) than that of conventional imaging, which detected (36%; 51 of the 139 women). More than 50 percent of DCIS components were detected with MRI alone. 

The researchers also found the sensitivity benefits of MR imaging over conventional imaging improved with increasing relative size, and with increasing nuclear grade of DCIS components. Positive margin rates were generally low and did not diverge significantly between the 139 women with DCIS components versus the 454 women who lacked them.

The authors concluded that breast MRI improves depiction of DCIS components of invasive breast cancers before surgery.

Breast MRI Without Contrast Detects Cancer.

According to a study published in Radiology a radiomics technique that is based on diffusion weighted imaging with an adapted kurtosis model reduces false-positive results in both malignant and benign breast lesions when compared with x-ray mammography.

This institutional study included 222 women at two study sites (site 1: training set of 95 patients; mean age of 58.6 years; with 61 malignant and 34 benign lesions; and site 2: independent set of 127 patients; mean age, 58.2 years with 61 malignant with 66 benign lesions). 

Among all 222 patients, histopathology results confirmed malignant lesions in 122 women (55%); invasive ductal carcinoma was the most common finding, in 90 patients (74%). Benign lesions were found in the remaining 100 women (45%); fibrosis (21 patients, 21%) and fibroadenoma (20 patients, 20%) were the most common abnormalities.

All women presented with findings suspicious for cancer at x-ray mammography (BI-RADS 4 or 5) and an indication for biopsy. Before biopsy, diffusion-weighted MR imaging (b values, 0–1500 sec/mm²) was performed by using 1.5-T imagers from different MR imaging vendors. Lesions were segmented and voxel-based kurtosis fitting adapted to account for fat signal contamination was performed. Conventional interpretations of MR imaging were also assessed for comparison.

The kurtosis radiomics model reduced false-positive results from 66 to 20 (specificity 70.0% [46 of 66]) at the predefined sensitivity of greater than 98.0% [60 of 61] in the independent test set, with BI-RADS 4a and 4b lesions benefiting from the analysis (specificity 74.0%, [37 of 50]; 60.0% [nine of 15]) and BI-RADS 5 lesions showing no added benefit. The model significantly improved specificity compared with the median apparent diffusion coefficient (P < .001) and apparent kurtosis coefficient (P = .02) alone. Conventional reading of dynamic contrast material–enhanced MR imaging provided sensitivity of 91.8% (56 of 61) and a specificity of 74.2% (49 of 66). Accounting for fat signal intensity during fitting significantly improved the area under the curve of the model (P = .001).

 The authors concluded the radiomics model based on kurtosis diffusion-weighted imaging allowed for reliable differentiation between malignant and benign breast lesions.

Breast MRI is the study of choice for women at high risk for breast cancer.

According to a study published in Radiology Lo et al reviewed the outcomes of 3,934 screening breast studies (MRI and mammograms) performed on 1,249 high-risk women. A total of 45 cancers (33 invasive and 12 ductal carcinomas in situ) were diagnosed, 43 were seen with MR imaging and 14 with both mammography and MR imaging.   The cancer detection rate for MR imaging was 21.8 cancers per 1000 examinations and that for mammography was 7.2 cancers per 1000 examinations. Sensitivity and specificity of MR imaging were 96% and 78% respectively, and those of mammography were 31% and 89%, respectively (P < .001).  The researchers reported that all cancers found at screening mammography were also detected on breast MRI.  

The researchers concluded that annual screening mammography adds no value to women that are at high risk for breast cancer especially since they are screened each year with breast MRI.

Preoperative Breast MRI detects additional cancers

A paper by Bae et al published in Radiology indicates that preoperative MRI in women whose breast cancer was detected by ultrasound found additional cancers.

The study was a retrospective review of 374 women, median age, 48 years, with breast cancer detected at screening ultrasound.

Of 374 women, 21 or 5.6% patients were diagnosed with additional cancer.  In premenopausal women with invasive breast cancer and in those with index invasive lobular histologic type had higher incidence of additional cancer detected at MR imaging.  Premenopausal status also put the women at risk.

The authors concluded that preoperative MRI detected additional sites of cancer in women with breast cancer detected at screening ultrasound.

Breast MRI more accurate than mammography in diagnosing invasive cancer in high-risk women

A study by Sung et al published in Radiology found that breast MRI screening is more likely to detect invasive cancers than mammography in women at higher risk. 

The study was a retrospective review of 7,519 high-risk women due to family or personal history of breast cancer, high risk lesion, BRCA mutation status or radiation to the chest, who underwent MRI screening and mammography.

A total of 18 064 screening MR imaging examinations and 26 866 screening mammographic examinations were performed. Two hundred twenty-two cancers were diagnosed in 219 women, 167 (75%) at MR imaging, 43 (19%) at mammography, and 12 (5%) interval cancers. Median age at diagnosis was 52 years.  Cancers found at screening MR imaging were more likely to be invasive cancer 118 of 167 or 71%. Of the 43 cancers found at screening mammography, 38 (88%) manifested as calcifications and 28 (65%) were ductal carcinoma in situ. Interval cancers were associated with nodal involvement were of the triple-negative subtype.

In conclusion MRI of the breast was better than mammography in detecting invasive breast cancer in women at high risk for breast cancer.  Mammography had an advantage for the detection of calcifications and thus for ductal carcinoma in situ.