Imaging

Imaging work-up is undertaken as part of triple assessment in a new patient clinic. Patients are normally examined prior to imaging. Imaging is not required for all patients and may be omitted in cases of low clinical suspicion and normal or benign examination.

The UK RCR system of scoring index of suspicion is commonly used for all imaging, ranging from 1-5, as follows:

1. Normal / no significant abnormality: There is no significant imaging abnormality.
2. Benign findings: The imaging findings are benign.
3. Indeterminate / probably benign findings: There is a small likelihood of malignancy. Further investigation is indicated.
4. Findings suspicious of malignancy: There is a moderate likelihood of malignancy. Further investigation is indicated.
5. Findings highly suspicious of malignancy: There is a high likelihood of malignancy. Further investigation is indicated.
6. Known biopsy proven malignancy*

*this forms part of the American college of Radiologists BIRADS scoring system but is being adopted in the UK.

Ultrasound

Ultrasound should be used as the first line imaging modality in the following cases

1. Women aged under 40 years of age, without a clinical suspicious examination 
2. Women aged 40 years and over, without a clinical suspicious examination who have had a mammogram within the last six months
3. During pregnancy and lactation.

Ultrasound should be used as the second line imaging modality following mammography UNLESS there is a low index of clinical suspicion, and the mammogram is benign/normal when ultrasound can therefore be omitted.

In potentially suspicious cases to assess for multifocality, whole breast ultrasound is recommended. A minimum of index lesion whole quadrant USS (ultrasound) should be performed.

Mammography

Mammography is indicated upfront when there is clinical suspicion of malignancy (E5).

Should include mediolateral oblique (MLO) and craniocaudal (CC) views of each breast with additional views as appropriate.

Mammography is also indicated in the following cases

1. Women ≥40yrs UNLESS a mammogram has been performed within six months and there is a low level of clinical suspicious
2. Women aged <40yrs when ultrasonically suspicious findings, preferably before undertaking a biopsy.
3. All patients with confirmed breast cancer or DCIS.

Advanced mammographic imaging techniques

Digital breast tomosynthesis (DBT) provides additional morphological information and is helpful in delineating outlines of masses and distortions. It is especially helpful in heterogenous and extremely dense breast tissue.

Contrast enhanced mammography (CEM) is emerging as a valuable resource in evaluating multifocality in the breast, and with the appropriate software, can be performed as per local availability policy.

Axillary Imaging

Ultrasound of the axilla should be performed in all patients when malignancy is suspected or confirmed.

The imaging report should document the number of abnormal nodes seen.

Core biopsy should be performed rather than fine needle aspiration cytology (FNAC) unless core biopsy technically not feasible. Insertion of a tissue marker into the biopsied node should be performed according to local protocols.

Sampling of at least one node is indicated in the following:

1. Abnormal morphology (e.g., Absence of fatty hilum, round shape)
2. Increased cortical thickness based on radiological suspicion and local policies, usually ≥ 4mm

Tissue markers

Tissue markers may be inserted at the time of biopsy of suspicious lesions. Tissue markers ideally should be inserted into suspicious lymph nodes at the time of initial biopsy.

Generally, tissue markers should be considered initially but particularly in the following situations:

1. Small (<15 mm) lesions.
2. Neoadjuvant (NACT) settings prior to starting the treatment

Indications for MRI (with contrast)

Following MDT discussion, if breast conserving surgery is being considered:

• Pre-operatively in lobular cancer (or mixed invasive with a lobular component)
• A size discrepancy between the clinical and radiological findings
• Multifocal or multicentric disease
• Radiological concern regarding breast density and potential of occult lesions
• Mammographically occult tumours
• Paget’s disease of the nipple
• In malignant axillary node(s) with no primary tumour evident on conventional imaging
• Patients undergoing neoadjuvant chemotherapy where it would influence clinical decision making
• In suspected recurrence where conventional triple assessment has not provided a definitive diagnosis

Contrast enhanced mammography (CEM)

CEM has comparable accuracy to dynamic contrast-enhanced MRI for T-staging and assessing for multiple primary tumour foci in most instances.

The current NICE guideline¹ for early and locally advanced breast cancer: diagnosis and management published in July 2018 does not include recommendations regarding staging. This is covered in the national RCR guidance.

Only a small (4-6%)² proportion of patients with breast cancer have metastatic disease at presentation. In view of this, formal staging with cross sectional imaging is not required in the majority of patients.

Breast cancer stage is based on the anatomic clinical stage within the 8th edition of the AJCC cancer staging manual³:

The following guidance applies to the use of Computerised Tomography (CT) in patients with a new diagnosis of breast cancer.

CT Staging to assess for Metastatic disease

Contrast-enhanced CT of the chest, abdomen and pelvis, including supraclavicular fossae and proximal femora is indicated in the following situations:

1. T3 and T4 primary cancer
2. ≥ 4 abnormal nodes on axillary ultrasound or ≥ 4 macrometastatic nodes at axillary surgery
3. Symptoms suspicious for metastatic disease

Advanced imaging techniques

Following MDT discussions further imaging modalities including PET and whole-body MRI may be considered with specific questions, for example

• Patients with oligometastatic disease who may be suitable for advanced radiotherapy treatment (SABR)
• Patients with inflammatory cancer: consider FDG PET-CT

Clinical concern of CNS disease: CT head with contrast should be included.

Neoadjuvant endocrine therapy

Interval imaging with ultrasound +/- mammography is adequate.

Neoadjuvant chemotherapy

Contrast enhanced MRI is the most accurate technique for response monitoring and can be used as per local policy. There needs to be consideration if a mammogram and ultrasound are also required.

Imaging during/after neoadjuvant chemotherapy requires individual planning based on extent of disease, visibility of disease on relevant modalities and ultimate surgical plan.  Options include mammography, ultrasound and MRI. 

Where MRI is not performed at the end of chemotherapy, as a minimum, ultrasound +/- mammogram should be performed at baseline and end of treatment.

Midcycle MRI imaging can be performed if result would influence chemotherapy regimen. However, assessment with USS can be used as alternative.

As per guidance for imaging women, first-line investigation for suspicion lesion:

• ≥ 40 years: perform mammography
• <40 years: consider performing ultrasound and/or mammography as clinically indicated

Axillary USS should always be performed to assess axillary nodes.

Initial imaging modality is USS. Mammography should be performed once there is biopsy proven malignancy.

Mammography

Mammography in pregnant patients is safe to perform, with minimal radiation risk to the foetus, although informed discussions should take place prior to mammogram. Patients should be informed that mammographic sensitivity is reduced and there is a small increased radiation dose to the breast.

Lactating patients can breast feed or express milk prior to mammography to help reduce breast density.

Contrast-enhanced MRI

MRI sensitivity is reduced during pregnancy and lactation due to the increased background parenchymal enhancement pattern.

Contrast enhanced MRI in pregnancy should be limited, with gadolinium-based contrast agent only being administered if there is a benefit to the patient that significantly outweighs the potential risk of exposing the foetus to the contrast agent. 

Patients who are lactating must be counselled regarding limitations of the technique during this time. There is negligible excretion of gadolinium into breast milk.

References:

1. National Institute for Health and Care Excellence. Early and locally advanced breast cancer: diagnosis and management [Internet]. [London]: NICE; 2018. (Clinical guideline [CG101]). 
2. Royal College of Radiologists (RCR). Guidance on screening and symptomatic breast imaging [Internet]. [London]: RCR; 2019. (BFCR(19)9). 
3. Amin MB, Edge SB, Greene FL, et al, eds. AJCC Cancer Staging Manual. 8th ed. New York, NY: Springer; 2017.
4. Mammography-Reporting.pdf (acr.org)
5. Retrospective preoperative assessment of the axillary lymph nodes in patients with breast cancer and literature review : B Saffar M Bennett C Metcalf S Burrows, Clin Radiol. 2015 Sep;70(9):954-9.doi: 10.1016/j.crad.2015.04.019.