The overall sensitivity of MRI in women at high familial risk varies between different studies from 71% to 100%. Importantly the sensitivity is not modified by the density of the breast [24]. A meta-analysis of 11 studies showed a sensitivity of 77% for the performance of MRI alone and 94% when MRI was combined with mammography, compared to 39% for mammography alone [22]. One of the explanations that has been given regarding the variation between published studies is the unusual MRI imaging features in this group. Frequently, these tumours demonstrate benign kinetic features and often present with non-mass like enhancement [23]. Additionally, these lesions appear with smooth, non-infiltrative borders, without architectural distortion or space-occupying effects on T1- or T2-weighted images. Consequently, the specificity of MRI in these populations varies between 79% and 95%. These particular features give an explanation for the lower detectability of familial breast cancer and emphasises that the significance of this type of finding should not be underestimated when identified [23].

The cancer detection rate reported for MRI alone in different prospective cohort studies ranges from 8.2 to 15.9 per 1000 [9, 11, 16, 18, 22]. Different studies demonstrate similar or increased detection rates in BRCA1 and BRCA2 mutation carriers and their first-degree relatives compared to women with a family history of breast/ovarian cancer with no documented mutation [24]. Additionally, the detection rate of MRI varied among different age groups. Chiarelli and colleagues identified a higher cancer detection rate for MRI alone in women who were over 50 years old compared to women younger than 50 years old [25]. A number of studies have suggested that in high-risk women, MRI has an increased sensitivity in identifying multifocal and multicentric disease, compared to breast ultrasound and mammography [11, 24].

The ability of MRI to detect breast cancers, virtually uninfluenced by the density of breast parenchyma in familial high-risk women [21], led the National Institute for Health and Care Excellence [5] and the GC-HBOC [26] to recommend annual MRI alone, and not in combination with mammography, for familial high-risk women between the ages of 30 and 39, who do not have a prior diagnosis of the disease. It has been recommended by some that the starting age for MRI screening should be adjusted according to the age of diagnosis in the youngest affected relative, with MRI screening commencing 5 years earlier than this age, and according to the type of mutations (BRCA1, BRCA2 or TP53) as age-specific risks vary [27]. UK NICE guidelines advise MRI screening should commence at age 20 in TP53 gene carriers compared to age 30 in BRCA gene carriers [5]. Most recommendations suggest continuing intensified surveillance, including MRI, at least until the age of 50. Nevertheless, Sardanelli and colleagues found that the effectiveness of MRI continues even after the age of 50 [24]. However, cost issues must also be taken into account by health funding agencies when developing guidelines.

The rates of interval cancers in familial high-risk patients undergoing MRI surveillance may be as high as 40% [11]. Annual MRI surveillance is associated with a significant increase in the incidence of smaller size cancers in BRCA2 carriers. However, this was less frequently observed in BRCA1 carriers, where some women presented with palpable interval cancers, between 6 and 12 months after a normal annual screening MRI [28]. This observed difference might be due to the faster rate of tumour growth in BRCA1 carriers, given the fact that BRCA1-associated cancers are frequently triple negative and of basal phenotype, which are usually high grade and with a very high proliferation index [22]. Interestingly, Tilanus-Linthorst and colleagues [29] reported a significant difference in the doubling time of tumours between BRCA mutation carriers and noncarriers. The reported doubling time for carriers was 45 days compared to 84 days for noncarriers [29]. Therefore, some high-risk screening programmes recommend 6-month surveillance with CBE and/or breast ultrasound in addition to regular annual screening with MRI or alternating MRI and mammography every 6 months, so BRCA1 carriers are offered a shorter interval between screening rounds.

Despite the higher sensitivity of MRI compared to mammography, it remains unclear whether MRI leads to decreased mortality from breast cancer. Up until now, no randomised trial has been designed to directly compare mortality reduction offered by mammography versus MRI; the existing evidence is only indirect and further research is urgently needed.

The estimated indirect benefit that has been achieved from MRI surveillance is derived from downstaging of breast cancer, where the small size and noninvasiveness of breast cancers have been used as reasonable proxy indices for cancer survival [11]. In BRCA1-associated breast cancer diagnosed in an MRI-based surveillance programme, the 10-year survival rate for cancers less than 1 cm was 93%, compared to 58% for cancers measuring from 1 to 2 cm [30]. Documented evidence has shown that BRCA1 tumours are more aggressive and that size is not an ideal criterion for improved survival since these tumours tend to metastasize early and small tumours may often already have positive lymph nodes [31]. According to earlier studies, BRCA1 patients had a 73–74% 5-year survival [32, 33]. Nevertheless, a more recent study reported a 10-year survival equal to 81%; data suggested that once prognostic factors are taken into account, the outcome among carriers is similar to noncarriers [34].

Apart from the high cost, the most important problems regarding breast MRI are its low specificity, high false-positive recall rates and low sensitivity for detecting DCIS; nevertheless, the latter seems of minor importance since DCIS is rare in BRCA 1 carriers. With continual improvements in MRI technology, specificity has improved. In addition, mammography and second look ultrasound substantially increases the specificity of MRI [35]. Modern MRI units, with high field strength, with a minimum standard of at least 1.5 Tesla, a dedicated bilateral breast coil, quality control visits on a regular basis and experienced radiologists are some of the requirements for high-quality MRI screening. In addition, substantial reporting expertise is needed and some health systems recommend double reading to ensure quality. Furthermore MRI examination is not feasible in certain women due to claustrophobia or contraindications, such as pacemakers, metallic implants, morbid obesity (many scanners have a weight limit), inability to lie prone for up to an hour or renal dysfunction precluding the use of contrast agents [36]. Cost prohibits its use for many health economies in the world.

In a recently published work, Kuhl and colleagues introduced an ultra-fast, 3-min, breast MRI for cancer screening. The results of this study showed that ultra-fast breast MRI substantially reduces the time of image acquisition as well as it decreases the reading time and cost of the exam, displaying a comparable sensitivity and specificity to that of conventional MRI in the screening setting [37].