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

Purpose: To evaluate the feasibility and toxicity profile of repeated stereotactic body radiotherapy (SBRT) for recurrent primary or secondary liver tumors. Methods: 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. Results: 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, EQD2 ₁₀  = 70.5) Gy and 48 (range 27–66 Gy, EQD2 ₁₀  = 71) Gy for the re-SBRT. The median mean liver dose (D _{mean, liver} ) was 6 Gy (range 1–25, EQD2 ₂  = 7 Gy) for the first SBRT and 10 Gy (range 1–63 Gy, EQD2 ₂  = 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. Conclusions: 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.