Intrinsic susceptibility MRI can inform on tumour vascular decompression in response to the stromal targeted therapy PEGPH20

PEGPH20 has been shown to decompress blood vessels and improve tumour drug delivery. Given the sensitivity of R₂* to paramagnetic deoxyhaemoglobin and reflection of RBC content in tumour vasculature, we hypothesised that IS-MRI may provide a useful biomarker of PEGPH20 response. We performed IS-MRI before and after PEGPH20 treatment in 4T1 HAS3 and MDA-MB-231 LM2-4 orthotopic breast tumours. R₂* significantly increased following PEGPH20 treatment in 4T1 HAS3 tumours, however, R₂* was unable to detect a similar response to PEGPH20 in the relatively hypovascular MDA-MB-231 LM2-4 tumours. Another vascular biomarker may provide greater sensitivity and detect PEGPH20 response in hypovascular tumours.