Current emerging MRI tools for radionecrosis and pseudoprogression diagnosis

Abstract

Purpose of review This review aims to cover current MRI techniques for assessing treatment response in brain tumors, with a focus on radio-induced lesions. Recent findings Pseudoprogression and radionecrosis are common radiological entities after brain tumor irradiation and are difficult to distinguish from real progression, with major consequences on daily patient care. To date, shortcomings of conventional MRI have been largely recognized but morphological sequences are still used in official response assessment criteria. Several complementary advanced techniques have been proposed but none of them have been validated, hampering their clinical use. Among advanced MRI, brain perfusion measures increase diagnostic accuracy, especially when added with spectroscopy and susceptibility-weighted imaging. However, lack of reproducibility, because of several hard-to-control variables, is still a major limitation for their standardization in routine protocols. Amide Proton Transfer is an emerging molecular imaging technique that promises to offer new metrics by indirectly quantifying intracellular mobile proteins and peptide concentration. Preliminary studies suggest that this noncontrast sequence may add key biomarkers in tumor evaluation, especially in posttherapeutic settings. Summary Benefits and pitfalls of conventional and advanced imaging on posttreatment assessment are discussed and the potential added value of APT in this clinicoradiological evolving scenario is introduced.

Focal cavity radiotherapy after neurosurgical resection of brain metastases: sparing neurotoxicity without compromising locoregional control

“…In the case of a suspected local relapse, MRI perfusion [ 8 ] and PET scan with F‑18-fluorethyltyrosin (FET) were used for non-invasive distinction between tumor relapse and radionecrosis. In case of persistent suspicion of local tumor regrowth, neurosurgical resection of the lesion was recommended to the patient.…”

Imaging Glioblastoma Response to Radiotherapy Using 2H Magnetic Resonance Spectroscopy Measurements of Fumarate Metabolism

“…Tumor water ADC has been reported to be lower in true disease progression as compared to pseudoprogression, however meta-analyses have shown that while diagnostic performance was superior to that of conventional anatomical imaging it was poorer when compared to MRI measurements of perfusion (13). Dynamic (32,(35)(36)(37)(38). However, while meta-analysis has shown that 1 H MRS is superior to anatomical MRI, DWI-MRI and MRI-based perfusion measurements in distinguishing true progression from pseudoprogression (39) the low signal-to-noise ratio in spectroscopy means that scan times are long.…”

Salvage Treatment for Progressive Brain Metastases in Breast Cancer

“…Several diagnostic modalities may help to differentiate between PRN and tumor progression. That includes MRI spectroscopy, positron emission tomography, single-photon emission computed tomography, and high-resolution MRI with the assessment of perfusion and diffusion [ 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. However, the only 100% reliable method of confirmation of progressive BCBM after SRS/FSRT is a pathological examination of the resected tumor.…”