Comparison of interstitial high-dose-rate brachytherapy and stereotactic radiotherapy in breath-hold technique for inoperable primary and secondary liver tumors

Background and purpose

In recent years, ablative radiotherapy of primary and secondary liver tumors has become a highly regarded treatment option. We aimed to compare high-dose-rate interstitial brachytherapy (HDR-iBT) and stereotactic body radiotherapy (SBRT) in free breathing (FB) and deep inspiration breath hold (DIBH) in order to support future decisions on the appropriate radiation technique for liver tumors.

Materials and methods

Forty-two patients with 1–4 liver malignancies undergoing HDR-iBT with 1x15-20 Gy were included. Eighty-eight SBRT plans in DIBH or FB with a prescription dose of 3x12.5 Gy to the surrounding 67 % isodose were generated using the HDR-iBT-computed tomography. Dose-volume parameters according to ICRU91 regarding organs-at-risk (OAR), target coverage, generalized equivalent uniform dose (gEUD_2Gy), biological dose parameters, dose uniformity, conformity and plan quality indices were compared.

Results

The mean target doses for HDR-iBT were at least twice as high as in SBRT, but target coverage was significantly more conformal for SBRT and the gEUD_2Gy was higher (p < 0.001). The healthy tissue conformity indices (HTCI) for SBRT_FB and SBRT_DIBH were significantly higher than for HDR-iBT (p < 0.001). For all techniques, a significant positive correlation between HTCI and target volume size was found. HDR-iBT achieved lower mean and maximum doses for most investigated OAR-parameters. Comparing SBRT_DIBH and SBRT_FB, all OAR-parameters presented significantly lower values for SBRT_DIBH (p < 0.001).

Conclusion

While SBRT_DIBH achieved a more conformal target coverage with both higher minimal doses and gEUD_2Gy, brachytherapy offered higher mean and maximal doses to the target volume and a better sparing of OAR, depending on optimal catheter positioning.