Breast Imaging

Population risk

• >95% population, <1.5x population risk, <15% lifetime risk

Intermediate risk

• <4% population, 1.5-3x population risk, 15-19% lifetime risk
• Includes dense breasts, personal history of breast cancer, atypia on previous biopsy (ADH 4x, lobular neoplasia 2.4-12x), proliferative changes without atypia 1.5-2x)

High risk

• <1% population, >3x population risk, >20% lifetime risk
• Includes high risk genetic mutations, significant family history, previous mantle radiotherapy

• Dense breasts include Category D (extremely dense, approx. 10% population) and Category C (heterogeneously dense, approx .40% population)
• Women with dense breasts have a higher risk of developing breast cancer than women with fatty breasts, and the risk of missing a breast cancer is increased in dense breasts due to the masking effect of dense tissue
• The risk of developing breast cancer associated with extremely dense breasts is 4-6 x that of fatty breasts.

Whilst 2D mammography has been shown to be effective in detecting breast cancer, additional investigations may provide increased rate of cancer detection, and this may be particularly beneficial in women who are at higher risk of developing breast cancer, including those with dense breasts.

Additional tests include:

• DBT/tomosynthesis/3Dmammography
• Breast ultrasound
• Contrast enhanced mammography
• Breast MRI, including abbreviated breast MRI

These tests are all available at North Shore Radiology and Nuclear Medicine.

DBT (digital breast tomosynthesis)/ 3D mammography

• DBT is shown to have higher cancer detection rate than 2D mammography, particularly in dense breasts
• DBT reduces need for additional unnecessary investigation due to overlapping normal tissue
• We routinely use DBT (3D mammography) in place of 2D mammography because of its ability to detect more breast cancers than 2D mammography and it leads to fewer additional potentially unnecessary investigations because of its ability to better differentiate normal overlapping tissue from true breast lesions.

• The radiation dose for DBT is comparable to 2D mammography and the experience of having DBT is like having a 2D mammogram.

Compared with 2D mammography:

• DBT will find an additional (0.7-2.7 (2.3)) cancers per 1000 women

• Ultrasound will find an additional 2-5 cancer per 1000 women
• Contrast enhanced mammography will find 7-13 cancers per 1000 women
• MRI will find an additional 10-20 cancers per 1000 women

Breast Ultrasound

• is often recommended as an additional test to mammography because of its ability to find additional cancers, particularly in dense breasts
• it does not use ionising radiation or require contrast injection
• for lesions seen on ultrasound it provides a simple and usually very well tolerated way to perform breast biopsy.
• A disadvantage is that it may find lesions that are not breast cancer, but these will require additional investigation (such as additional short-term review or biopsy)

Contrast enhanced mammography

• Is a more recently developed test which is essentially a mammogram following injection of Iodine contrast, showing tumour neovascularity as well as morphology
• has higher cancer detection rate than DBT, with comparable cancer detection rate to MRI
• is more widely available than MRI across the world, able to be “added” to existing mammography machines, is cheaper to implement than MRI and generally better tolerated /preferred by women than MRI.
• Takes about same time as 2D mammogram, requires IV cannulation prior to mammogram
• Disadvantages include
  • additional radiation c/w 2D (between 20-80% higher than 2D if 3D plus CEM)
  • need for contrast – Iodine (same as CT scan contrast) with small risk of contrast reaction
  • allergic reactions <1% usually mild/self-limiting, (severe 0.01-0.04%)

Breast MRI

Current indications:

• high risk surveillance – (rebate)
• new diagnosis breast cancer – clinical discrepancy (rebate) , dense, pretreatment planning
• node positive with unknown primary (rebate)
• problem solving – conventional inconclusive, biopsy not possible (rebate)
• implant assessment
• neoadjuvant response
• post treatment surveillance (if cancer under 50 – rebate till age 60)
• moderate risk
• dense breasts

requires gadolinium contrast IV (exception implant assessment)

specialist referred Medicare rebate for specified indications

takes 20-30 mins

Disadvantages:

• cost
• claustrophobia (position prone in magnet)
• requires Gadolinium IV

Abbreviated breast MRI

• Technology advances mean most significant information can be acquired rapidly, with shorter scan time, approximately 10 mins, similar to CEM.
• Shorter scan time more comfortable and acceptable to women
• Similar cancer detection rate to full sequence
• Allows greater access to MRI scans, cheaper than full scan
• Still requires Gadolinium

Considerations:

• Risk, including density are important factors to consider in recommending most suitable screening.
• Current screening recommendations across the world vary.
• Most current guidelines for supplemental screening are limited to women at high risk.
• Formal risk assessment models vary and are not readily available to all women.
• For women at intermediate risk advice regarding supplemental screening is particularly variable.
• Patient preference will also be an important factor.

For screening:

Recommend risk assessment from age 25

• iPrevent tool – see Cancer Australia website, does not include density
• RACGP accepted clinical resource, takes ~30mins
• Tyrer Cuzick – currently research tool, commercial use requires licence –(watch this space)

For women at population risk age 40 and over:

• BreastScreen Australia:
  • available for 2^nd year 2D mammogram with no density measure as “minimum” screening
• NSRNM – for women who prefer or require increased level of cancer detection:
  • DBT +/-US  at minimum
  • If first imaging and density unknown – 3D mammogram/DBT +/- ultrasound, and density will inform next screening recommendation
  • If dense at first screen ( for all Category D, and consider for Category C), with no other risk factors recommend CEM or abbreviated MRI for next screen in 12 months, then treat as moderate risk with recommendation for contrast imaging every 2 years

For women at Intermediate/moderate risk, including women with dense breasts:

Note:

• Eusobi (European Society of breast Imaging) recommend MRI every 2-4 years in women with extremely dense breasts
• ACR (American College of Radiology) recommend yearly MRI for women who have had breast cancer diagnosed under age 50, and for women who have cancer treatment at any age in dense breasts.

NSRNM recommends:

• Annual screening from age 40
• At minimum use DBT +/- US yearly
• Consider contrast imaging (either CEM or abbreviated MRI according to preference) at least very second year, alternating with DBT +/- US
•  Prefer MRI to CEM
  • For surveillance following cancer diagnosis under age 50
  • For surveillance following cancer any age, dense breasts
  • For implants
  • Iodine allergy
• Consider CEM in preference to MRI if over age 60

 For women at high risk:

• Referral to High-Risk Clinic
• Annual screening breast MRI from age 25 to 30 till age 60
• DBT +/- US