Whole-body diffusion-weighted magnetic resonance imaging for the detection of bone metastases and their prognostic impact in metastatic renal cell carcinoma patients treated with angiogenesis inhibitors.

Metastatic renal cell carcinoma (mRCC) patients with bone metastases (BM) are at high risk for skeletal related events and have a poorer outcome when treated with vascular endothelial growth factor receptor-tyrosine kinase inhibitors (VEGFR-TKIs). Computed tomography (CT) lacks sensitivity to detect BM in mRCC. We aimed to determine the added value of whole body diffusion-weighted magnetic resonance imaging (WB-DWI/MRI) to CT for the detection of BM in mRCC and to estimate the prognostic impact of the number of BM in mRCC patients treated with VEGFR-TKIs. We conducted a prospective study including consecutive mRCC patients treated with a first-line VEGFR-TKI in the metastatic setting. All patients underwent a pretreatment thoracic-abdominal-pelvic CT and WB-DWI/MRI. CT and WB-DWI/MRI were compared for the detection of BM. The number of detected BM was correlated with response rate (RR), progression-free survival (PFS) and overall survival (OS) after start of the VEGFR-TKI. Ninety-two patients were included. BM were found in 55% of the patients by WB-DWI/MRI and in 43% of the patients by CT ( = .003). Mean number of BM discovered per patient was 6.8 by WB-DWI/MRI versus 1.9 by CT ( = .006). The cutoff of ≤5 versus >5 BM on WB-DWI/MRI had the highest discriminative power for all outcome measures. Patients with >5 BM had a lower RR (10% versus 42%), more frequently early progressive disease (43% versus 13%,  = .003), shorter PFS (4 versus 10 months,  = .006) and shorter OS (10 versus 35 months,  < .0001) compared to patients with ≤5 BM. WB-DWI/MRI detects significantly more BM in mRCC patients than CT, allowing better estimation of the prognostic impact of BM in mRCC patients treated with VEGFR-TKIs. The prognostic impact should now be validated in patients treated with immune checkpoint inhibitors.