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Radiosensitivity differences between liver metastases based on primary histology suggest implications for clinical outcomes following SBRT.
Background: Increasing evidence in the management of oligometastases with stereotactic body radiotherapy (SBRT) reveals differences in outcomes based on primary histology and dose selection. We have previously identified a multigene expression index for tumor radiosensitivity (RSI) with validation in multiple independent cohorts. In this study, we assessed RSI in liver metastases and our clinical outcomes following SBRT based on primary histology. Methods: Patients were identified from our institutional IRB approved prospective observational protocol. A total of 444 metastatic liver lesions were obtained from a de-identified meta-data pool. Gene expression was from Affymetrix Hu-RSTA-2a520709. The RSI 10 gene assay was run on tissue samples and calculated using the previously published algorithm. A cohort of 33 patients with 38 liver metastases treated with SBRT using 50 Gy or 60 Gy in 5 fractions was used for clinical correlation. Results: The median RSI for all liver lesions was 0.42 (Q1, 0.28; Q3, 0.49). The most common primary histology for liver metastases were colorectal (n = 374; 81%), pancreas (n = 18; 4%), and breast (n = 15; 3%). There were significant differences in RSI of liver metastases based on histology. The median RSIs for liver metastases in descending order of radioresistance were skin (0.54), colorectal (0.43), stomach (0.43), pancreas (0.42), lung (0.35), breast (0.34), small intestine (0.22), and anal (0.21); p = 0.0003. A total of 57 patients had multiple liver tissue samples. When averaging RSI values from the same patient, significant differences continued to be noted based on primary histology: colorectal (0.43), lung (0.43), breast (0.34), and anus (0.20); p = 0.008. The 12 and 24 month Kaplan-Meier rate of local control (LC) for colorectal lesions was 79% and 59% compared to 100% for non-colorectal lesions (p = 0.019), respectively. Conclusions: In this first analysis assessing the radiosensitivity of liver metastases, we find significant differences based on primary histology. As we move towards an era of personalized radiation delivery, this study suggests primary histology may be an important factor to consider in SBRT dose selection.
Abstracts by Kamran A. Ahmed:
Differences between colon cancer primaries and metastases utilizing a molecular assay for tumor radiosensitivity and implications for potential oligometastatic SBRT patient selection.Meeting: 2015 Gastrointestinal Cancers Symposium | Abstract No: 569
- Meeting: 2014 ASCO Annual Meeting | Abstract No: 5065