Abstract

Stereotactic body radiation therapy (SBRT) is the only non-invasive local therapy for the treatment of hepatocellular carcinoma (HCC) and is often utilized following transarterial embolization. There is a paucity of data reporting safety and outcomes of patients (pts) receiving SBRT after yttrium-90 (Y90). We evaluated the impact of Y90 and SBRT composite plan dosimetry on toxicity and outcomes of HCC pts. An IRB-approved registry of 260 liver SBRT pts was used. Pts included in analysis received Y90 prior to SBRT and had post-90Y PET imaging (measuring Bremsstrahlung component of Y90). Volume of ablated liver was estimated using the sharp edge of PET gradient and the SBRT volume receiving at least 30 Gy (V30). Characteristics between groups were compared using Chi-square and independent t-test. Clinical, imaging, and laboratory follow up are reported. Twenty eights pts with median follow up of 14 m (4.6-49.6) were included. Pts received 1 (N = 15), 2 (N = 10), or 3 (N = 3) prior Y90 treatments, to a median volume of 286 cm3 (21-1512) a median 4.4 m (1.1-82.9) prior to SBRT. SBRT dose ranged from 24-50 Gy in 3-5 fractions with a median PTV of 117 cm3 (26-857). Y90 and V30 overlap ranged from 0-577 cm3 with a median of 80 cm3. Treatment intent was definitive in 23 pts, to downstage within transplant criteria in 4 pts, and as a bridge to transplant in 1 pt. Baseline Child-Pugh (CP) score was A, B, and C in 23, 3, 2 pts, respectively. At a median 9 m (1.5-46.4) after SBRT local control was 93%. Liver, nodal, and distant failure had an incidence of 11%, 3.6%, and 11%, respectively. Change in CP score was analyzed at 1-2 m and 3 m post SBRT. Twenty-six patients had at least one calculable time point. Change in CP class from A to B was seen in 6 pts (26%), of which two recovered back to CP A by 3 m. The 3 CP B pts did not change class, and the 2 CP C pts received successful liver transplants 2-3 m after SBRT downstaging. Factors associated with an increase in CP score within 3 m of SBRT include SBRT mean liver dose (P = 0.001), SBRT V30 (P = 0.049), and <1200 cm3 of un-ablated liver (P = 0.003). Volume of liver treated by Y90 and time between Y90 and SBRT was not associated with an increase in CP score within 3 m of SBRT. Non-hematologic toxicity includes 2 acute biliary stricture (grade 2-3), 1 late biliary stricture (grade 2), 1 late chest wall pain (grade 1), and 1 late grade 2 radiographic myonecrosis. One CP A pt died 4 weeks after SBRT of cardiopulmonary comorbidities. Time between Y90 and SBRT, volume of liver exposed to prior Y90, and overlap between V30 and Y90 volumes do not appear to adversely impact CP score within 3 m of SBRT. In addition to known dosimetric properties including mean liver dose, and V30, we found that un-ablated liver volume <1200 cm3 was associated with an increase in CP score within 3 m of SBRT in this cohort of pts. Pts with HCC previously treated with Y90 appear to tolerate SBRT well with no clinically significant change in CP score, minimal toxicity, and excellent local control.

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