Abstract
AIMS: Brain metastases (BMs) from different primary cancers may have different radiosensitivity, for example melanoma and renal cell cancers are considered more radioresistant. Radiosensitivity is determined by the intrinsic radiobiological properties of tumours, which include vascularisation and oxygenation. Contrast Clearance Analysis (CCA)-MRI measures delayed contrast behaviour to offer a window into tumour vascularity. The CCA colour map shows areas of contrast accumulation (red), suggesting vascular damage, and rapid contrast clearance (blue), suggesting intact and increased vasculature. We aim to interrogate CCA-MRIs pre-stereotactic radiosurgery (SRS) for differences in contrast handling between BMs from different primaries. METHOD: 10 patients, with 70 BMs, were included in the study. All had CCA-MRIs pre-SRS as part of their planning-MRIs. Radiotherapy-planning-CT scans were fused with the planning-post-contrast-T1-MRI, with consultant clinical oncologist-approved contoured targets, and the CCA-images. Threshold analysis was performed to obtain proportions of red and blue within the enhancing areas of each tumour. RESULTS: There was a significant difference in the proportion of blue between BMs from different primaries (p=0.0294). In pairwise-comparisons, only the difference between lung and renal was significant (mean difference 37.65%, p=0.0390). The difference between the proportion of red was also significant overall (p=0.0084) (Figure 2). In pairwise comparisons, renal was significantly different from lung, breast and melanoma (mean difference 12.65%, p=0.0161; mean difference 12.97%, p=0.0154; and mean difference 11.29%, p=0.0169, respectively). CONCLUSION: This study offers a novel insight into the vascularity of BMs from different primaries. Further research to explore if these findings can explain differential SRS outcomes is underway.