Validation of the liver mean dose in terms of the biological effective dose for the prevention of radiation-induced liver damage

Expression levels of KATP channel subunits and morphological changes in the mouse liver after exposure to radiation

BACKGROUND

ATP sensitive K⁺ (K_ATP) channels are ubiquitously distributed in various of cells and tissues, including the liver. They play a role in the pathogenesis of myocardial and liver ischemia.

AIM

To evaluate the radiation-induced changes in the expression of K_ATP channel subunits in the mouse liver to understand the potential role of K_ATP channels in radiation injury.

METHODS

Adult C57BL/6 mice were randomly exposed to γ-rays at 0 Gy (control, n = 2), 0.2 Gy (n = 6), 1 Gy (n = 6), or 5 Gy (n = 6). The livers were removed 3 and 24 h after radiation exposure. Hematoxylin and eosin staining was used for morphological observation; immunohistochemical staining was applied to determine the expression of K_ATP channel subunits in the liver tissue.

RESULTS

Compared with the control group, the livers exposed to 0.2 Gy γ-ray showed an initial increase in the expression of Kir6.1 at 3 h, followed by recovery at 24 h after exposure. Exposure to a high dose of 5.0 Gy resulted in decreased expression of Kir6.1 and increased expression of SUR2B at 24 h. However, the expression of Kir6.2, SUR1, or SUR2A had no remarkable changes at 3 and 24 h after exposure to any of these doses.

CONCLUSION

The expression levels of Kir6.1 and SUR2B in mouse liver changed differently in response to different radiation doses, suggesting a potential role for them in radiation-induced liver injury.

Effect of the normal liver mean dose on intrahepatic recurrence in patients with hepatocellular carcinoma after receiving liver stereotactic body radiation therapy

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The normal liver mean dosage is rarely studied in its association with metastasis related survival.

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Higher normal liver mean dosage was related to a better intra-hepatic progression free survival.

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No associations were found between normal liver mean dose with Local control rate, Overall Survival, Distant Metastasis Free Survival, Progression Free Survival.

Background and purpose

This study aims to evaluate whether dosimetric parameters affect the intrahepatic out-field recurrence or distant metastasis-free survival following the stereotactic body radiation therapy (SBRT) in patients with hepatocellular carcinoma (HCC).

Materials and methods

A total of 76 patients with HCC who were treated with SBRT from January 2015 to May 2020 were included in this retrospective study. The main clinical endpoints considered were intrahepatic out-field free survival (OutFFS) and distant metastasis-free survival (DMFS). The target parameters and the liver were documented including tumor diameters, gross tumor volume (GTV), Liver minus GTV volume (LGV), and Liver minus GTV mean dose (LGD). Multivariable Cox regression with forward stepwise selection was performed to identify independent risk factors for OutFFS and DMFS. Maximally selected rank statistics were used to determine the most informative cut-off value for age and LGD.

Results

The median follow-up was 28.2 months (range, 7.7–74.5 months). LGD higher than 12.54 Gy [HR, 0.861(0.747–0.993); p = 0.040] and age greater than 67-year-old [HR, 0.966(0.937–0.997); p = 0.030] are two independent predictors of OutFFS, previous TACE treatment [HR, 0.117(0.015–0.891); p = 0.038] was an independent predictor of DMFS.

Conclusions

The results of this study suggested that the higher the dose received by the normal liver (greater than 12.54 Gy) the better the intrahepatic out-field recurrence-free survival (RFS) rate. Further study is warranted to confirm and to better understand this phenomenon.

Preoperative Stereotactic Body Radiotherapy to Portal Vein Tumour Thrombus in Hepatocellular Carcinoma: Clinical and Pathological Analysis

The prognosis of hepatocellular carcinoma (HCC) with portal vein tumour thrombus (PVTT) is poor. We conducted a prospective study to evaluate the efficacy and safety of tri-modality therapy, including preoperative stereotactic body radiotherapy (SBRT) and surgery, followed by hepatic arterial infusion chemotherapy (HAIC) in HCC patients with PVTT. In this report, we investigated the pathology of the irradiated PVTT specimen in resected cases and SBRT-related acute toxicity. A total of 8 HCC patients with PVTT received preoperative SBRT targeting the PVTT at a dose of 48 Gy in 4 fractions at our institute from 2012 to 2016. Of the eight patients, six underwent surgery, while the remaining two did not because of disease progression. At the pathological examination, all patients’ irradiated PVTT specimens showed necrotic tissue, and three of six patients showed complete pathological response. Two patients showed 30% necrosis with high degeneration and one patient, with 30% necrosis without degeneration, was the only recurrent case found during the follow-up period (median: 22.5, range: 5.9–49.6 months). No SBRT-related acute toxicity worse than grade 2 was observed from SBRT to surgery. In conclusion, the preoperative SBRT for HCC was pathologically effective and the acute toxicities were tolerable.

Use of 3D biological effective dose (BED) for optimizing multi-target liver cancer treatments

The purpose is to calculate the composite 3D biological effective dose (BED) distribution in healthy liver, when multiple lesions are treated concurrently with different hypo-fractionated schemes and stereotactic body radiation therapy, and to investigate the potential of biological based plan optimization. Two patients, each having two tumors that were treated sequentially with different treatment plans, were selected. The treatment information of both treatment plans of the patients was used and their dose matrices were exported to an in-house MATLAB software, which was used to calculate the composite BED distribution. The composite BED distributions were used to determine if the healthy liver received BED beyond tolerance. When the dose to the minimum critical volume was less than tolerance, an optimization code was used to derive the scaling factors (ScF) that should be applied to the dose matrix of each plan until the minimum critical volume of healthy liver reaches a BED close to tolerance. It was shown that for each patient, there is a margin for dose escalation regarding the doses to the individual targets. More specifically, the ScFs of the doses range between 5.6 and 99 in the first patient, whereas for the second patient, the ScFs of the optimal doses range between 12.7 and 35.6. The present study indicates that there is a significant margin for dose escalation without increasing the radiation toxicity to the healthy liver. Also, the calculation of the composite BED distribution can provide additional information that may lead to a better assessment of the liver's tolerance to different fractionation schemes and prescribed doses as well as more clinically relevant treatment plan optimization.