Emerging and Evolving Concepts in Cancer Immunotherapy Imaging.

Criteria based on measurements of lesion diameter at CT have guided treatment with historical therapies due to the strong association between tumor size and survival. Clinical experience with immune checkpoint modulators shows that editing immune system function can be effective in various solid tumors. Equally, novel immune-related phenomena accompany this novel therapeutic paradigm. These effects of immunotherapy challenge the association of tumor size with response or progression and include risks and adverse events that present new demands for imaging to guide treatment decisions. Emerging and evolving approaches to immunotherapy highlight further key issues for imaging evaluation, such as dissociated response following local administration of immune checkpoint modulators, pseudoprogression due to immune infiltration in the tumor environment, and premature death due to hyperprogression. Research that may offer tools for radiologists to meet these challenges is reviewed. Different modalities are discussed, including immuno-PET, as well as new applications of CT, MRI, and fluorodeoxyglucose PET, such as radiomics and imaging of hematopoietic tissues or anthropometric characteristics. Multilevel integration of imaging and other biomarkers may improve clinical guidance for immunotherapies and provide theranostic opportunities.

Can MRI differentiate surrounding vertebral invasion from reactive inflammatory changes in superior sulcus tumor?

OBJECTIVES: Vertebral invasion is a key prognostic factor and a critical aspect of surgical planning for superior sulcus tumors. This study aims to further evaluate MRI features of vertebral invasion in order to distinguish it from reactive inflammatory changes. METHODS: Between 2000 and 2016, a retrospective study was performed at a single institution. All patients with superior sulcus tumors undergoing surgery, including at least two partial vertebrectomies, were included. An expert radiologist evaluated qualitative and quantitative MRI signal intensity characteristics (contrast-to-noise ratio [CNR]) of suspected involved and non-involved vertebrae. A comparison of CNR of invaded and sane vertebrae was performed using non-parametric tests. Imaging data were correlated with pathological findings. RESULTS: A total of 92 surgical samples of vertebrectomy were analyzed. The most specific sequences for invasion were T1 and T2 weighted (92% and 97%, respectively). The most sensitive sequences were contrast enhanced T1 weighted fat suppressed and T2 weighted fat suppressed (100% and 80%). Loss of extrapleural paravertebral fat on the T1-weighted sequence was highly sensitive (100%) but not specific (63%). Using quantitative analysis, the optimum cut-off (p < 0.05) to distinguish invasion from reactive inflammatory changes was CNR > 11 for the T2-weighted fat-sat sequence (sensitivity 100%), CNR > 9 for contrast-enhanced T1-weighted fat-suppressed sequence (sensitivity 100%), and CNR < - 30 for the T1-weighted sequence (specificity 97%). Combining these criteria, 23 partial vertebrectomies could have been avoided in our cohort. CONCLUSION: Qualitative and quantitative MRI analyses are useful to discriminate vertebral invasion from reactive inflammatory changes. KEY POINTS: • Abnormal signal intensity in a vertebral body adjacent to a superior sulcus tumor may be secondary to direct invasion or reactive inflammatory changes. • Accurate differentiation between invasion and reactive inflammatory changes significantly impacts surgical planning. T1w and T2w are the best sequences to differentiate malignant versus benign bone marrow changes. The use of quantitative analysis improves MRI specificity. • Using contrast media improves the sensitivity for the detection of tumor invasion.