Silent radiological imaging time in patients with brain metastasis

An estimate of rate of deviation from NCCN guideline recommendations for central nervous system imaging in trials forming basis for drug approval in first line advanced non-small cell lung cancer (NSCLC)

Importance

It is unknown whether and to what degree trials submitted to the US FDA to support drug approval adhere to NCCN guideline-recommended care in their baseline and surveillance CNS imaging protocols.

Objective

We sought to characterize the frequency with which the trials cited in US FDA drug approvals for first line advanced NSCLC between 2015 and 2020 deviated from NCCN guideline-recommended care for baseline and surveillance CNS imaging.

Design, setting, and participants

Retrospective observational analysis using publicly available data of (1) list of trials cited by the FDA in drug approvals for first line advanced NSCLC from 2015 to 2020 (2) individual trial protocols (3) published trial data and supplementary appendices (4) archived versions of the NCCN guidelines for NSCLC from 2009 to 2018 (the years during which the trials were enrolling).

Main outcomes and measures

Estimated percentage of trials for first line advanced NSCLC leading to FDA approval which deviated from NCCN guideline-recommended care with regards to CNS baseline and surveillance imaging.

Results

A total of 14 studies that had been cited in FDA drug approvals for first line advanced NSCLC met our inclusion criteria between January 1, 2015 and September 30, 2020. Of these trials, 8 (57.1%) deviated from NCCN guidelines in their baseline CNS imaging requirement. The frequency of re-assessment of CNS disease was variable amongst trials as well, with 9 (64.3%) deviating from NCCN recommendations.

Conclusions and relevance

The trials supporting US FDA drug approvals in first line advanced NSCLC often have CNS imaging requirements that do not adhere to NCCN guidelines. Many trials permit alternative, substandard methods and the proportion of patients undergoing each modality is uniformly not reported. Nonstandard CNS surveillance protocols are common. To best serve patients with advanced NSCLC in the US, drug approvals by the FDA must be based on trials that mirror clinical practice and have imaging requirements consistent with current US standard of care.

Volumetric Analysis of F-18-FET-PET Imaging for Brain Metastases

BACKGROUND

The knowledge of exact tumor margins is of importance for the treating neurosurgeon, radiotherapist, and oncologist alike. The aim of this study was to investigate whether tumor volume and tumor margins acquired by magnetic resonance imaging (MRI) are congruent with the findings acquired by O-(2-(18F)-fluoroethyl)-L-tyrosine-positron emission tomography (FET-PET).

METHODS

Patients received FET-PET and MRI before surgery for brain metastases. Metastases were quantified by calculating tumor-to-background uptake ratios using FET uptake. PET and MRI-based tumor volumes, as well as areas of intersection, were assessed.

RESULTS

Forty-one patients were enrolled in the study. The maximum tumor-to-background uptake ratio measured in all of our patients harboring histologically proven viable tumor tissue was >1.6. Absolute tumor volumes acquired by FET-PET and MRI were not congruent in our patient cohort, and tumors identified in FET-PET and MRI only partially overlapped. The ratio of intersection (intersection of tumor defined by MRI and tumor defined by FET-PET at the ratio of tumor defined by FET-PET) was within a range of 0.27-0.68 when applying the different thresholds.

CONCLUSIONS

Our study therefore indicates that treatment planning based on MRI or PET only might have a substantial risk of undertreatment at the tumor margins. These findings could have important implications for the planning of surgery as well as radiotherapy, although they have to be validated in further studies.

Rat model of metastatic breast cancer monitored by MRI at 3 tesla and bioluminescence imaging with histological correlation

Background

Establishing a large rodent model of brain metastasis that can be monitored using clinically relevant magnetic resonance imaging (MRI) techniques is challenging. Non-invasive imaging of brain metastasis in mice usually requires high field strength MR units and long imaging acquisition times. Using the brain seeking MDA-MB-231BR transfected with luciferase gene, a metastatic breast cancer brain tumor model was investigated in the nude rat. Serial MRI and bioluminescence imaging (BLI) was performed and findings were correlated with histology. Results demonstrated the utility of multimodality imaging in identifying unexpected sights of metastasis and monitoring the progression of disease in the nude rat.

Methods

Brain seeking breast cancer cells MDA-MB-231BR transfected with firefly luciferase (231BRL) were labeled with ferumoxides-protamine sulfate (FEPro) and 1-3 × 10⁶ cells were intracardiac (IC) injected. MRI and BLI were performed up to 4 weeks to monitor the early breast cancer cell infiltration into the brain and formation of metastases. Rats were euthanized at different time points and the imaging findings were correlated with histological analysis to validate the presence of metastases in tissues.

Results

Early metastasis of the FEPro labeled 231BRL were demonstrated onT2*-weighted MRI and BLI within 1 week post IC injection of cells. Micro-metastatic tumors were detected in the brain on T2-weighted MRI as early as 2 weeks post-injection in greater than 85% of rats. Unexpected skeletal metastases from the 231BRL cells were demonstrated and validated by multimodal imaging. Brain metastases were clearly visible on T2 weighted MRI by 3-4 weeks post infusion of 231BRL cells, however BLI did not demonstrate photon flux activity originating from the brain in all animals due to scattering of the photons from tumors.

Conclusion

A model of metastatic breast cancer in the nude rat was successfully developed and evaluated using multimodal imaging including MRI and BLI providing the ability to study the temporal and spatial distribution of metastases in the brain and skeleton.