Hybrid 18F–FDG PET/MRI might improve locoregional staging of breast cancer patients prior to neoadjuvant chemotherapy

Abstract

Purpose Our purpose in this study was to assess the added clinical value of hybrid 18 F-FDG-PET/MRI compared to conventional imaging for locoregional staging in breast cancer patients undergoing neoadjuvant chemotherapy (NAC). Methods In this prospective study, primary invasive cT2-4 N0 or cT1-4 N+ breast cancer patients undergoing NAC were included. A PET/MRI breast protocol was performed before treatment. MR images were evaluated by a breast radiologist, blinded for PET images. PET images were evaluated by a nuclear physician. Afterwards, a combined PET/MRI report was written. PET/MRI staging was compared to conventional imaging, i.e., mammography, ultrasound and MRI. The proportion of patients with a modified treatment plan based on PET/MRI findings was analyzed.Results A total of 40 patients was included. PET/MRI was of added clinical value in 20.0% (8/40) of patients, changing the treatment plan in 10% and confirming the malignancy of suspicious lesions on MRI in another 10%. In seven (17.5%) patients radiotherapy fields were extended because of additional or affirmative PET/MRI findings being lymph node metastases (n = 5) and sternal bone metastases (n = 2). In one (2.5%) patient radiotherapy fields were reduced because of fewer lymph node metastases on PET/MRI compared to conventional imaging. Interestingly, all treatment changes were based on differences in number of lymph nodes suspicious for metastasis or number of distant metastasis, whereas differences in intramammary tumor extent were not observed. Conclusion Prior to NAC, PET/MRI shows promising results for locoregional staging compared to conventional imaging, changing the treatment plan in 10% of patients and potentially replacing PET/CT or tissue sampling in another 10% of patients.

PET/MRI in Breast Cancer

“…In the same study by Grueneisen et al, PET/MRI and MRI alone correctly identified multifocal/multicentric disease in 8/9 patients, compared with 5/9 by PET/CT. Similar to Grueneisen et al, Goorts et al found that PET/MRI and MRI alone were equivalent for assessing breast tumor size and multifocality in 40 patients with breast cancer …”

“…Regarding changing axillary nodal status, Goorts et al reported one case of axillary downstaging and one case of axillary upstaging by PET/MRI compared with conventional imaging . One study evaluated the impact of dedicated axillary PET/MRI on axillary nodal status in 12 patients with clinically positive axillary nodal disease.…”

“…In 1999, Kinoshita et al reported a sensitivity of 93.3% and a specificity of 89.3% among 43 MRI‐detected IM nodes in 16 patients . In the above‐mentioned study of 40 patients by Goorts et al, PET/MRI detected one abnormal IM node not initially seen on MRI alone and increased diagnostic confidence in three other cases of IM metastases . Jochelson et al compared the prevalence of IM adenopathy identified by MRI with that by PET/CT.…”

“…However, the radiation dose and imaging, processing, and reading times associated with such an exam make it unlikely that this type of breast imaging will become part of our clinical routine. Instead, breast PET/MR may be more important before and during neoadjuvant therapy, where multiple layers of imaging parameters may eventually be converted into radiomic data that may lend increased precision to breast cancer treatments; and in local staging, where the improved evaluation of the axilla potentially afforded by PET/MRI may eventually preclude the need axillary lymph node tissue sampling . For breast cancer patients in need of whole‐body staging or posttreatment surveillance, PET/MR outperforms PET/CT at a much lower radiation dose .…”

Is the whole larger than the sum of the parts? Integrated PET/MRI as a tool for response prediction

“…The impact of FDG PET/CT on oncologic management decisions has also been presented [15]. Recently, the value of integrated PET/MRI on initial staging and therapy decision-making has been demonstrated [16,17].…”