Towards personalised dosimetry in patients with liver malignancy treated with 90Y-SIRT using in vivo-driven radiobiological parameters

Abstract

BackgroundThe prediction of response is one of the major challenges in radiation-based therapies. Although the selection of accurate linear–quadratic model parameters is essential for the estimation of radiation response and treatment outcome, there is a limited knowledge about these radiobiological parameters for liver tumours using radionuclide treatments.MethodsThe “clinical radiobiological” parameters (T_{{text{p}}}, T_{{text{k}}}, alpha, alpha {/}beta) for twenty-five patients were derived using the generalised linear–quadratic model, the diagnostic ([18F] FDG PET/CT) and therapeutic ([90Y]-SIR-Spheres PET/CT) images to compute the biological effective dose and tumour control probability (TCP) for each patient.ResultsIt was estimated that the values for alpha and alpha {/}beta parameters range in ≈ 0.001–1 Gy−1 and ≈ 1–49 Gy, respectively. We have demonstrated that the time factors, T_{{text{p}}}, T_{{text{k}}} and T_{{{text{critic}}}} are the key parameters when evaluating liver malignancy lesional response to [90Y]SIR-Spheres treatment. Patients with cholangiocarcinoma have been shown to have the longest average T_{{text{p}}} (≈ 236 ± 67 d), highest TCP (≈ 53 ± 17%) and total liver lesion glycolysis response (Delta {text{TLG}}_{{{text{liver}}}} ≈ 64%), while patients with metastatic colorectal cancer tumours have the shortest average T_{{text{p}}} (≈ 129 ± 19 d), lowest TCP (≈ 28 ± 13%) and Delta {text{TLG}}_{{{text{liver}}}} ≈ 8%, respectively.ConclusionsTumours with shorter T_{{text{k}}} have shown a shorter T_{{{text{critic}}}} and thus poorer TCP and Delta {text{TLG}}_{{{text{liver}}}}. Therefore, these results suggest for such tumours the [90Y]SIR-Spheres will be only effective at higher initial dose rate (e.g. > 50 Gy/day).