An updated review on the diagnosis and assessment of post-treatment relapse in brain metastases using PET

ABSTRACT

Introduction

Brain metastases in patients with extracranial cancer are typically associated with increased morbidity and mortality. Stereotactic radiotherapy and immunotherapy using checkpoint inhibitors currently are essential in brain metastases treatment. Since conventional contrast-enhanced MRI alone cannot reliably differentiate between treatment-induced changes and brain metastasis relapse, several studies investigated the role of PET imaging and, more recently, radiomics, based on routinely acquired PET images, to overcome this clinically relevant challenge.

Areas covered

The current literature on PET imaging, including radiomics, in patients with brain metastases, focusing on the diagnosis and assessment of post-treatment relapse, is summarized.

Expert opinion

Available data suggest that imaging parameters, including radiomics features, mainly derived from amino acid PET, are helpful for diagnosis and assessment of post-treatment relapse in patients with brain metastases.

KEYWORDS:

• Amino acid PET
• FET
• radiomics
• pseudoprogression
• radiation-induced changes
• checkpoint inhibitors

Article highlights

• Amino acid PET and newer PET probes have the potential to provide valuable additional diagnostic information in patients with brain metastases for differentiating treatment-related changes from post-treatment relapse induced by radiosurgery and checkpoint inhibitor immunotherapy.

• PET-based radiomics may provide valuable additional information for this clinically critical distinction.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Abbreviations

DCE = dynamic contrast-enhanced MR imaging; DSC PWI = dynamic susceptibility contrast-enhanced perfusion-weighted imaging; DWI = diffusion-weighted imaging; FDG = [¹⁸F]-2-fluoro-2-deoxy-D-glucose; FDOPA = 3,4-dihydroxy-6-[¹⁸F]-fluoro-L-phenylalanine; FET = O-(2-[¹⁸F]fluoroethyl)-L-tyrosine; MET = [¹¹C]-methyl-L-methionine; n = number; n.a. = not available; SUV = standardized uptake value; TBR_mean/max = mean or maximum standardized uptake value of the lesion divided by the maximum standardized uptake value of the reference region

Additional information

Funding

This paper was supported by funds from the Deutsche Forschungsgemeinschaft, grant: 428090865.