Yttrium-90 Microsphere-selective Internal Radiation Therapy With Chemotherapy (Chemo-SIRT) for Colorectal Cancer Liver Metastases

Objectives: Selective internal radiation therapy (SIRT) with yttrium-90 (90Y) microspheres has emerged as an effective liver-directed therapy with a favorable therapeutic ratio for treatment of colorectal cancer liver metastases. The aim of this study was to investigate the objective responses obtained by 90Y microsphere treatment when combined with contemporary chemotherapy in the front-line (first or second line) setting in patients with CRCLM. Methods: This study used an in vivo comparison between the right and left liver lobes; systemic chemotherapy was supplied to both liver lobes by virtue of systemic administration, whereas SIRT was administered selectively to the target liver lobe only. Response to treatment was evaluated by serial fludeoxyglucose positron emission tomography computed tomography performed at 4 weeks, 2 to 4 months, and 6 to 8 months. Standard uptake value, anatomic volume, functional tumor volume, and total lesion glycolysis (TLG) calculations were obtained at each time point. Results: A decrease in TLG on fludeoxyglucose positron emission tomography computed tomography imaging was seen in 19 of the 20 patients. The mean decrease in TLG values in the tumors receiving chemo-SIRT and chemo-only treatment were 86.26%±18.57% and 31.74%±80.99% (P<0.01), 93.13%±11.81% and 40.80%±73.32% (P=0.01), and 90.55%±19.75% and 54.91%±38.55% (P<0.01) at 4 weeks, 2 to 4 months, 6 to 8 months posttreatment, respectively. Functional and anatomic tumor volume changes were in concordance with the TLG changes. Conclusions: The study demonstrated that, under near identical conditions in terms of patient and tumor characteristics, the chemo-SIRT combination produced superior objective responses compared with chemo-only treatment in a front-line treatment setting in patients with colorectal cancer liver metastases.