PV QA 1 - Poster Viewing Q&A 1
Purpose/Objective(s):The purpose of the present study was to evaluate clinical outcomes following stereotactic body radiation therapy (SBRT) in patients with liver metastases (LM) due to colorectal cancer (CRC).
Materials/Methods:This was a single-institution retrospective study of patients included in a prospectively maintained institutional database. Outcome endpoints included overall survival (OS), local control (LC), progression-free survival (PFS), and extra- and intra-hepatic progression-free survival (EHPFS/IHPFS). Eligible patients had LM due to CRC, were treated with SBRT between 2007-2017, and had at least 3 months of follow up. We identified 55 patients that met these criteria; 13/55 (24%) of patients had prior partial hepatectomy. Median number of chemotherapy regimens prior to SBRT was 1 (range 0-3). The majority of patients (81.6%) had a solitary liver metastasis; 2 had extrahepatic disease at the time of SBRT. The maximum number of treated LM was 3. Median SBRT dose was 54 Gy (range 32-60 Gy) in 3 fractions (range 3-5), and median BED10 was 151.2 Gy. Median tumor diameter was 2.8 cm (range 0.4-5.6). All survival times were calculated from the start date of SBRT. Kaplan-Meier curves were used to estimate actuarial survival times, and Cox regression was used for multivariable analysis (MVA) of predictors of overall survival.
Results:At a median follow up of 44.5 mos (range 3-96), 24/55 patients (43.6%) of patients have died. Estimated median OS was not reached; estimated mean OS was 61.7 months (95% CI 51.7-71.7), and actuarial 5-year OS estimate was 21%. Median PFS was 13.0 months (95% CI 2.6-23.4); median IHPFS was 26 months (95% CI 15.4-36.4), longer than the estimated median EHPFS of 18 months (95% CI 9.4-26.6). The crude overall rate of hepatic progression was 60.0% (33/55), while the crude rate of extrahepatic progression was 65.4% (36/55). Crude local control was 76% (13/55). Median local control time was significantly longer in patients with higher biologic equivalent dose (BED); median LC was 24 mos vs not reached in patients with BED10 < vs > 150, p = 0.002. OS was also improved in patients with BED10 > 150 (median 32 mos vs not reached and 5-yr OS 29 vs 58% in patients with BED10 < vs > 150, p = 0.03). Cox MVA showed that early local failure was associated with poorer OS (p = 0.004); higher baseline CEA at the time of treatment was also associated with a trend towards worse OS (p = 0.063).
Conclusion:SBRT is very effective in the management of hepatic oligometastases and was associated with an estimated mean OS of over 5 years in selected patients. In this series, 56% of patients who underwent liver SBRT for oligometastatic CRC remain alive after a median follow up of nearly 4 years (median 44.5 months). Overall LC was excellent and was strongly associated with higher BED. Early local progression was also associated with inferior OS, supporting efforts to achieve as high a BED as possible in SBRT plans for oligometastatic CRC.
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