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Stereotactic radiosurgery (SRS) and immune checkpoint inhibitors (ICI) are highly effective treatments for brain metastases, particularly when these therapies are administered concurrently. However, there are limited data reporting the risk of radiation necrosis (RN) in this setting. Patients with brain metastases from primary non-small cell lung cancer, renal cell carcinoma, or melanoma treated with SRS and ICI were considered. Time-to-event analyses were conducted for any grade RN and symptomatic RN (SRN) with death incorporated as a competing risk. As a secondary analysis, recursive partitioning analysis (RPA) was used for model development, and a loop of potential models was analyzed, with the highest-fidelity model selected. Brain V12 Gy thresholds identified on RPA were then incorporated into the competing risks analysis. Concurrent SRS and ICI administration. Six hundred fifty-seven patients with 4182 brain metastases across 11 international institutions were analyzed. The median follow-up for all patients was 13.4 months. The median follow-up was 12.8 months and 14.1 months for the concurrent and nonconcurrent groups, respectively (P =.03). The median patient age was 66 years, and the median Karnofsky Performance Status was 90. In patients with any grade RN, 1- and 2-year rates were 6.4% and 9.9%, respectively. In patients with SRN, 1- and 2-year rates were 4.8% and 7.2%, respectively. On RPA, the highest-fidelity models consistently identified V12 Gy as the dominant variable predictive of RN. Three risk groups were identified by V12 Gy: (1) < 12 cm3; (2) 20 cm3 ≥ V12 Gy ≥ 12 cm3; (3) V12 Gy > 20 cm3. In patients with any grade RN, 1-year rates were 3.7% (V12 Gy < 12 cm3), 10.3% (20 cm3 ≥ V12 Gy ≥ 12 cm3), and 12.6% (V12 Gy > 20 cm3); the 2-year rates were 7.5% (V12 Gy < 12 cm3), 13.8% (20 cm3 ≥ V12 Gy ≥ 12 cm3), and 15.4% (V12 Gy > 20 cm3) (P < 0.001). In patients with any SRN, 1-year rates were 2.4% (V12 Gy < 12 cm3), 8.9% (20 cm3 ≥ V12 Gy ≥ 12 cm3), and 10.3% (V12 Gy > 20 cm3); the 2-year rates were 4.4% (V12 Gy < 12 cm3), 12.4% (20 cm3 ≥ V12 Gy ≥ 12 cm3), and 13.1% (V12 Gy > 20 cm3; P < 0.001). There were no statistically significant differences in rates of any grade RN or SRN when accounting for therapy timing for all patients and by V12 risk group identified on RPA. The use of SRS and ICI results in a low risk of any grade RN and SRN. This risk is not increased with concurrent administration. Therefore, ICI can safely be administered within 4-weeks of SRS. Three risk groups based on V12 Gy were identified, which clinicians may consider to further reduce rates of RN. [ABSTRACT FROM AUTHOR]

Purpose: To report the toxicities and outcomes for stereotactic body radiation therapy (SBRT) and accelerated hypofractionated radiation therapy (AHRT) in patients with Child-Pugh (CP) class A, B, or C and albumin-bilirubin (ALBI) score 1, 2, or 3 hepatocellular carcinoma.Methods and Materials: We retrospectively reviewed the data from 146 patients with hepatocellular carcinoma who had undergone SBRT (50 Gy in 5 fractions) or AHRT (45 Gy in 18 fractions). The primary endpoint was liver toxicity, defined as an increase in the CP score of ≥2 within 6 months of radiation therapy. The secondary endpoints of ALBI change, overall survival, and local control were also calculated.Results: The median follow-up was 23 months (range 1-59). Most received SBRT (72%), and 28% received AHRT. Of all 146 patients, 45 (31%) had a CP score elevation of ≥2 within 6 months of radiation therapy (RT) (27 patients [28%] with baseline CP-A/B7 and 18 [35%] with baseline CP-B8/B9/C cirrhosis; P = .45). On multivariate analysis, neither baseline CP nor ALBI score was predictive of toxicity. No patient with a decline in liver functionality of CP ≥2 within 6 months of RT returned to baseline at later time points. Eleven grade 4 toxicities were observed. The mean change in the raw ALBI score at ∼6 months was similar for all baseline ALBI groups. Twenty-two patients underwent orthotopic liver transplantation after RT, 13 of whom had baseline CP-B8/B9/C liver functionality. For all patients, the 1- and 2-year treated-lesion local control was greater for SBRT than for AHRT (2-year 94% vs 65%, P < .0001).Conclusions: The tolerability of SBRT or AHRT as measured by a CP score decline of ≥2 within 6 months of RT was similar across baseline liver functionality groups. Compared with AHRT, SBRT was associated with superior local control. Because the true tolerability of limited-volume RT for patients with CP-B or CP-C cirrhosis is unknown, prospective trials validating its safety and efficacy are warranted. [ABSTRACT FROM AUTHOR]