Hepatobiliary scintigraphy allows the evaluation of short-term functional toxicity of liver stereotactic body radiotherapy: Results of a pilot study

Abstract

Purpose: To study the potential of (99m)Tc-Mebrofenin hepatobiliary scintigraphy (HBS) in identifying the short-term variations of liver function after stereotactic body radiotherapy (SBRT) for liver cancers.

Material and methods: We treated with SBRT 3 patients (pts) affected by a cholangiocarcinoma and 3 patient presenting liver metastases (3x15 Gy, 4 pts; 5x8 Gy, 1 pt; 6x5 Gy, 1 pt). All patients received HBS before and 3 months after SBRT, which were co-registered with the simulation CT-scan. Structures corresponding to isodoses from 10-90 Gy were created, with intervals of 10 Gy. Finally, the variations of the mean activity (MBq) in each isodose structure have been calculated. Then, a linear regression analysis was performed.

Results: We showed a linear reduction of the activity, significantly related to the delivered dose (p<0.01), and a reduction of the perfusion of 0.78% for each delivered Gy. The linear equation has predictive value of the loss of the function of 96% (R2 = 0.9605).

Conclusions: HBS could improve treatment plans for liver SBRT, by allowing the identification of the liver function variations after SBRT and, potentially, the prediction of remnant liver function after SBRT. These preliminary results should be confirmed on long-term prospective data and larger population.

Fig 1. A typical image in our study: In red the 20 Gy isodoses (EQD2), in white the 10 Gy (EQD2) for a patient treated with VMAT.

In green, the cropped structure (10–20 Gy crop). In this cropped structure we calculated the difference in the mean activity before and after radiotherapy. The same kind of structures and analyses were performed for all the so-obtained crop structures, calculated and defined with an interval of 10 Gy (EQD2). In violet we showed the PTV.

Fig 2. Results of the linear regression analysis.