Yttrium-90 Hepatic Radioembolization for Advanced Chemorefractory Metastatic Colorectal Cancer: Survival Outcomes Based on Right- Versus Left-Sided Primary Tumor Location.

Primary colon cancer location affects survival of patients with metastatic colorectal cancer (mCRC). Outcomes based on primary tumor location after salvage hepatic radioembolization with Y resin microspheres are not well studied. The objectives of this study are to assess the survival outcomes of patients with advanced chemorefractory mCRC treated with Y radioembolization, as stratified by primary tumor location, and to explore potential factors that are predictive of survival. A total of 99 patients who had progressive mCRC liver metastases while receiving systemic therapy and who were treated with Y radioembolization at a single center were retrospectively analyzed. For 89 patients, tumor response on the first imaging follow-up examination (CT or MRI performed at a mean [± SD] of 1.9 ± 0.9 months after Y radioembolization) was evaluated using RECIST. Overall survival (OS), OS after Y radioembolization, and hepatic progression-free survival (PFS) were calculated using the Kaplan-Meier method. Outcomes and associations of outcomes with tumor response were compared between patients with left- and right-sided tumors. A total of 74 patients had left-sided colon cancer, and 25 patients had right-sided colon cancer. Median OS from the time of mCRC diagnosis was 37.2 months, median OS after Y radioembolization was 5.8 months, and median hepatic PFS was 3.3 months. Based on RECIST, progressive disease on first imaging follow-up was observed in 38 patients (43%) after Y radioembolization and was associated with shorter OS after Y radioembolization compared with observation of disease control on first imaging follow-up (4.0 vs 10.5 months; < .001). Patients with right-sided primary tumors showed decreased median OS after Y radioembolization compared with patients with left-sided primary tumors (5.4 vs 6.2 months; = .03). Right- and left-sided primary tumors showed no significant difference in RECIST tumor response, hepatic PFS, or extrahepatic disease progression ( > .05). Median survival after Y radioembolization was significantly lower among patients with progressive disease than among those with disease control in the group with left-sided primary tumors (4.2 vs 13.9 months; < .001); however, this finding was not observed in the group with right-sided primary tumors (3.3 vs 7.2 months; = .05). Right-sided primary tumors were independently associated with decreased survival among patients with chemorefractory mCRC after Y radioembolization, despite these patients having a similar RECIST tumor response, hepatic PFS, and extrahepatic disease progression compared with patients with left-sided primary tumors. Primary colon cancer location impacts outcomes after salvage Y radioembolization and may help guide patient selection.