Repeated SBRT for in- and out-of-field recurrences in the liver

To evaluate the feasibility and toxicity profile of repeated stereotactic body radiotherapy (SBRT) for recurrent primary or secondary liver tumors.

Consecutive patients with primary (hepatocellular carcinoma [HCC] or cholangiocarcinoma [CCC]) or secondary liver cancer (LM), with intrahepatic recurrence or progression after SBRT, underwent re-SBRT in 3 to 12 fractions with a median time of 15 (range 2-66) months between treatments.

In all, 24 patients which were previously treated with SBRT (30 lesions) were retreated with SBRT for "in- and out-of-field" recurrences (2nd SBRT: n = 28, 3rd SBRT: n = 2). The median follow-up after re-irradiation was 14 months. The median prescribed dose for the first SBRT was 46.5 (range 33-66 Gy, EQD2₁₀ = 70.5) Gy and 48 (range 27-66 Gy, EQD2₁₀ = 71) Gy for the re-SBRT. The median mean liver dose (D_{mean, liver}) was 6 Gy (range 1-25, EQD2₂ = 7 Gy) for the first SBRT and 10 Gy (range 1-63 Gy, EQD2₂ = 9 Gy) for the re-SBRT. Of the 30 re-irradiated lesions 6 were re-irradiated in-field resulting in a median EQD2_{2, maximum} of 359 (range 120-500) Gy for both treatments, with an α/β = 2 to account for liver parenchyma. Treatment was well tolerated. Two patients with stent placement before SBRT developed cholangitis 4 and 14 months after re-SBRT. There were no elevations of the serum liver parameters after re-SBRT. One patient developed a grade 3 gastrointestinal bleeding. There was no radiation induced liver disease (RILD) observed.

Repeated liver SBRT is feasible, without excessive liver toxicity, when there is no considerable overlapping with pre-irradiated portions of the stomach or bowel and enough time for the liver to regenerate.