High lung shunt fraction in colorectal liver tumors is associated with distant metastasis and decreased survival.

PURPOSE: To assess how intratumoral shunting relates to liver metastasis and to clinical outcome.

MATERIALS AND METHODS: Lung shunt fraction (LSF) was calculated from macroaggregated albumin scan after transcatheter injection of radioactive particles in 62 patients with colorectal cancer and liver metastases evaluated for selective internal radiation therapy (SIRT) from May 2007 to August 2012. Assessment was performed of how LSF, liver tumor burden, and systemic chemotherapy relate to survival and the presence of lung metastases. LSF and tumor burden were also assessed in a subset of patients who underwent genetic profiling with SNaPshot analysis.

RESULTS: Patients with higher LSF were more likely to have lung metastases and decreased survival, whereas tumor burden was not associated with these outcomes. Patients with genetic mutations had significantly higher LSF than patients with no mutations. Patients who received chemotherapy before SIRT and had low LSF had the longest survival after SIRT.

CONCLUSIONS: LSF may be a more robust marker of metastasis than tumor size. Increased LSF secondary to vascular shunting within liver metastasis is an indicator of distant lesions and is associated with decreased survival after SIRT. Intratumoral shunting may provide a conduit for circulating tumor cells to access more remote organs, bypassing filtration by liver parenchyma, and may be an important factor in metastasis from colorectal cancer.