Editorial board note : This article is probably outdated, lacks structure and is in need of a major re write. If you are interested in refining it you are more than welcome
Sequences used
T1
T2
T1 C+ (Gd) : dynamic and kinetic analyisis
Lexicon
density
background enhancement :
none / minimal : < 25%
mild : 25 - 50%
moderate : 50 - 75%
marked : > 75%
focus < 5 mm : cannot characterize margins, etc.
mass enhancement :
shape : round, oval, lobulated, irregular
margins : smooth, irregular, speculated
internal : homogenous, heterogenous, rim, dark or enhancement, internal septations, central(target)
non mass enhancement :
focal, linear ductal, linear clumped, segmental patchy/clumped, regional, diffuse
stippled, punctuate, bilateral symmetric. It is important to scan both breasts for comparison.
linear enhancement :
enhancement kinetics : see >> breast MRI enhancement curves
washout, plateau, persistent (caveat: papillomas and lymph nodes washout)
~ 70% of invasive cancers wash out
~ 9% of DCIS washes out
Assessment categories
BIRADS 0 : use very sparingly; confirming lymph node or fibroadenoma on ultrasound or confirming benign process on mammogram and mammogram not available
BIRADS II : lymph nodes, inflamed cysts, fibroadenoma, fat necrosis, foci/stippled enhancement, background enhancement.
BIRADS IIIA : short term follow-up (in ~ 1 - 3 months) no mass likely hormonal enhancement (day 7-14 unless patient has known cancer for EOD eval or 2 - 3 weeks off hormone replacement therapy.
BIRADS IIIB : 6 mo. f/u for mass enhancement after having evaluated for benign morphology and kinetics -Prob. Benign: < 5 mm w/o rim enhancement, spiculation or washout
BIRADS IIIA & B : follow for 2 years (6 moonth, 1 year, 2 year.) (whereas mammo 3 years; 24% of 1st time MRI given BI-RADS 3; 0-10% cancer rate (3% MSKCC; small invasive cancers and DCIS)
It is important to remember that as most MRIs of the breast are performed on high risk population, 17% of smooth masses on 1st MRI were cancer (2/3 DCIS/ 1/3 Invasive). Thus one must not apply the same rules as to ultrasound on low risk patient; i.e. if washes out the lesion needs to be biopsied.
Similarly ductal enhancement should always prompt a biopsy.
Interpretation points
Clinical history and correlation with mammography is always useful and can reduce assignment of BIRADS III category.
Cancer detection highest in postmenopausal and for extent of disease (EOD) evaluation (22%) and lowest in premenopausal women for high risk screening (10%)
Positive predictive value (PPV) of MRI
in high risk screening population : 3 - 4% prevalence when mammography was negative ( 0.3 % when mammo and ultrasound negative)
7% if personal history of cancer
positive predictive value 24% ( ½ invasive 4 mm median size/ ½ DCIS). Biopsy recommended in 17%
Extent of disease (EOD)
contralateral breast :
5 % prevalence
20 % positive predictive value (biopsy recommended in 1/3) (NEJM 3/29/07: Bx rec in 12 % PPV 25 %);
Ipsilateral breast :
~ 25 %
50% PPV (biopsy recommended in 50%)
Ipsilateral multifocal ¾ (same quadrant > 1cm from index CA or contiguous but extends > 4 cm) multicentric ¼; distribution similar to recurrent disease
Additional sites of ipsilateral cancer more frequent if +FH (42%) & ILC (55%)
Positive predictive value higher the closer the lesion is to the index cancer.
Biopsy to get histological diagnosis no matter how suspicious because result is Mx
Younger patients because of 1 - 2% / year recurrence may also benefit from preop MRI
True and false positive rate decreases with each subsequent comparison MRI
MRI sensitivity
IDC / ILC : > 90%
DCIS : 80 - 90%
Implant rupture : ~ 94 % 9
Indications for breast MRI
ACR guidelines
high risk screening :
personal history
family history
high risk lesions : ADH / ALH / LCIS
BRCA1 / BRCA2 gene positivity
mantle radiotherapy (>4 Gray)
Li-Fraumeni syndrome + / - first-degree relatives
Cowden and Bannayan-Riley-Ruvalcaba syndromes and first-degree relatives
extent of disease (EOD) evaluation in ipsilateral and contralateral breast
positive margins (better accuracy further from lumpectomy site than near Lx site b/c postop enh/changes)
neo-adjuvant chemotherapy : to assess residual disease
metastatic axillary lymphadenopathy of unknown primary (75 - 80% sensitive) - can spare a patient from having Mx b/c may be able to undergo BCT; Mx path only finds cancer in 2/3
posterior lesion to assess chest wall invasion (pectoralis can be resected so not considered
chest wall stage IIIB- serratus anterior, rib, intercostal muscles)
ACS recommendations
BRCA+ : BRCA 1 or BRCA 2
1st degree relative BRCA+ and untested
those who have had prior radiotherapy to chest wall
> 25% lifetime risk based on genetic models (some of which take breast density into consideration)
not recommended if lifetime risk < 15 % because of high false positive rate
Other possible indications
problem solving (e.g. post operative breasts with distortion)
recurrent breast cancer / scar changes (not usual before 2 - 3 years; peak 5 - 7 years; increased risk if EIC, younger age, positive margins (wait at least 1 month post op to scan), no RT)
to assess for synchronous, multifocal or multicentric disease
MRI features and PPV
Mass
spiculated mass : 80 %
irregular shape : 32 %
< 5 mm mass : 3 %
Non mass
calcifications
segmental : 67 %
clumped ductal : 31 %
Ductal enhancement
malignant causes : DCIS, invasive cancer
benign high risk causes : ADH, LCIS
benign : fibrosis, ductal hyperplasia, fibrocystic change
MRI detected cancers
40 - 50 % cancers should be < 1 cm
at least 20 - 30% should be DCIS
positive nodes < 20%
False negatives
technical causes : breast tissue not included in the coil, motion, bad contrast injection, too much compression
marked background enhancement
Caveat : if mammography or ultrasound is positive or palpable finding need to treat / biopsy / excise despite negative MRI !
Ultrasound correlation
MSKCC : only 23% probably low but if lesion is less than 1 cm or deep within lots of background parenchyma in a large breast may want to go directly to MR guided biospy.
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