FDG-PET predicts outcomes of treated bone metastasis following palliative radiotherapy in patients with hepatocellular carcinoma

Aims: To determine the utility of FDG-PET in predicting long-term infield tumour control after RT in patients with metastatic hepatocellular carcinoma (HCC) to bone. Methods: Among 223 patients with HCC skeletal metastases diagnosed, we reviewed 22 patients with 45 total sites treated with RT who had at least two FDG-PETs prior to and after RT. The median RT dose was 42 Gy (range, 22-48) with a median fraction of 3 Gy (range, 2-8). Helical tomotherapy was generally offered for lesions that received higher RT dose (36%). The intrahepatic control rate in all patients was 73% at the time of referral. The ratio of tumour SUV to blood-pool activity SUV (SUV-ratio) was calculated. The primary end-points were infield progression-free survival (infield-PFS) and infield event-free survival (infield-EFS; recurrent and intractable pain or skeletal-related events). Results: Among 45 sites, 20 had tumour progression and 21 developed events in the previously treated area. A higher SUV-ratio before RT, SUV-ratio decline and higher radiation dose were independently and significantly correlated with better infield-PFS (both P < 0.05). The tumours with a pre-RT SUV-ratio ≥3.0 and SUV-ratio decline ≥40% had significantly better infield-PFS and EFS than those with either a pre-RT SUV-ratio <3.0 or SUV-ratio decline <40% (both P < 0.05). Conclusions: FDG-PET may help to predict outcomes of infield tumour control following palliative RT for treatment of HCC bone metastases. Tumours with low metabolic uptake before RT or with a minor decline in post-RT SUV-ratio showed poor long-term infield tumour control.