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

Abstract

Aim

The purpose of this study was to determine the optimal mean liver biologically effective dose (BED) to prevent radiation-induced liver disease (RILD) in stereotactic body radiation therapy (SBRT).

Background

The actual mean doses appropriate for liver irradiation in modern radiotherapy techniques have not been adequately investigated, although SBRT is sometimes alternatively performed using fractionated regimens.

Materials and methods

SBRT treatment plans for liver tumors in 50 patients were analyzed. All distributions of the physical doses were transformed to BED₂ using the linear-quadratic model. The relationship between physical doses and the BED₂ for the liver were then analyzed, as was the relationship between the mean BED₂ for the liver and the planning target volume (PTV).

Results

A significantly positive correlation was observed between the mean physical dose for the background liver and the mean BED₂ for the whole liver (P[[ce:hsp sp="0.25"/]]<[[ce:hsp sp="0.25"/]]0.0001, r[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]0.9558). Using the LQ model, a mean BED₂ of 73 and 16[[ce:hsp sp="0.25"/]]Gy for the whole liver corresponded to the hepatic tolerable mean physical dose of 21 and 6[[ce:hsp sp="0.25"/]]Gy for Child–Pugh A- and B-classified patients, respectively. Additionally, the PTV values were positively correlated with the BEDs for the whole liver (P[[ce:hsp sp="0.25"/]]<[[ce:hsp sp="0.25"/]]0.0001, r[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]0.8600), and the background liver (P[[ce:hsp sp="0.25"/]]<[[ce:hsp sp="0.25"/]]0.0001, r[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]0.7854).

Conclusion

A mean BED₂ of 73 and 16[[ce:hsp sp="0.25"/]]Gy for the whole liver appeared appropriate to prevent RILD in patients with Child–Pugh classes A and B, respectively. The mean BED₂ for the liver correlated well with the PTV.