Gastrointestinal Cancer

PV QA 1 - Poster Viewing Q&A 1

SU_15_2150 - Radiobiologically-Guided Radiation Therapy in Large Primary and Metastatic Hepatic Lesions

Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3

Radiobiologically-Guided Radiation Therapy in Large Primary and Metastatic Hepatic Lesions
D. Sit1, J. Snir2,3, S. Gaede2,4, E. Wong3, and M. I. Lock3,4; 1Michael G. DeGroote School of Medicine, McMaster University, Hamilton, ON, Canada, 2Western University, London, ON, Canada, 3London Regional Cancer Program, London, ON, Canada, 4London Health Sciences Centre, London, ON, Canada

Purpose/Objective(s): Radiobiologically-guided radiotherapy (RT) for hepatic lesions is an emerging treatment modality, however most prospective studies have included patients with smaller lesions, often ≤2 cm. This aim of this study is to report outcomes for patients who underwent radiobiologically-guided RT for large hepatic lesions of hepatocellular carcinoma (HCC) or metastases (MET). Size, as a stratification variable, was evaluated in terms of the toxicity, overall survival (OS) and progression free survival (PFS).

Materials/Methods: This single-institution database study included 107 patients with lesions >2 cm treated between 2004 to 2012. Patients were stratified based on previously proposed size criteria for management of hepatic lesions with ablative radiation; we identified 44 patients with medium (>2 to ≤5 cm), 47 with large (>5 to <10 cm) and 16 with huge (>10 cm) lesions. Radiation dose prescriptions varied between 29 to 88 Gy in 5 to 25 fractions using individualized radiobiological guidance. OS was evaluated by the Kaplan-Meier method and log-rank tests. Differences in rates of acute and late grade toxicities among the three size stratifications were evaluated by chi2.

Results: Our series included 44 HCC and 63 METs patients. Median diameter of medium, large and huge lesions were 3.5, 7.0 and 12.8 cm, respectively. Child-Pugh (CP) class was A, B and C in 76.6%, 22.4% and 0.9% of patients respectively. OS for cohort was OS for the cohort was 47.6% at 12 months and 30.9% at 24 months. On univariate analysis, factors significant to OS were: large lesions (hazard ratio, HR=1.8, p=0.014), huge lesions (HR=1.9, p=0.034), CP of B or C (HR=3.1, p=0.00), previous chemoembolization (HR=0.50, p=0.027) and equivalent dose in 2Gy fractions as a continuous variable (EQD2) (HR=0.98, p=0.001). All factors, aside from huge lesions, remained significant on multivariate analysis. PFS at 12 months was 26.2%. On univariate analysis, significant factors affecting PFS included extrahepatic disease (HR=1.6, p=0.032), previous chemoembolization (HR=0.51, p=0.029) and large lesion status (HR=1.6, p=0.031). These remained significant on multivariate analysis. There were 42 episodes of acute grade 2 toxicities and 13 episodes of acute grade 3 toxicities, while there were 25 episodes of late grade 2 toxicities and 13 episodes of late grade 3 toxicities. There were no grade 4 toxicities. Observed toxicities included fatigue (n=45), abdominal pain (n=40), rectal bleeding (n=2) and nausea (n=6). Between different lesions sizes, rates of grade 1-3 toxicities were not significantly greater in the acute setting (chi2=4.1, p=0.67 ) or the late setting (chi2=6.5, p=0.37).

Conclusion: Lesion size was a significant variable related to worse OS and PFS, but not rates of toxicity. Individualized radiobiological constraints appear to result in the ability to treat large lesions safely.

Author Disclosure: D. Sit: None. J. Snir: None. S. Gaede: None. M.I. Lock: Independent Contractor; London Health Sciences. Speaker's Bureau; Abbvie. Advisory Board; Accuray.

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