The findings are the result of a post-hoc analysis of more than 700 patients in the SIRFLOX and FOXFIRE global studies looking at the effects of SIRT. Adding the treatment to chemotherapy improves median overall survival by 4.9 months, translating into a 36% reduction in the risk of death at any given time, according to the research team led by Dr. Guy van Hazel, clinical professor of medicine at the University of Western Australia in Perth. He presented the data at the World Congress on Gastrointestinal Cancer (WCGC) in Barcelona, Spain.
Van Hazel and colleagues examined data from 739 patients, evaluating the addition of SIRT with liver-directed SIR-Spheres yttrium-90 (Y-90) resin microspheres to standard first-line mFOLFOX6 chemotherapy.
Of the patients, 179 (24.2%) had a right-sided primary tumor and 540 (73.1%) had a left-sided primary tumor. Only 16 (2.2%) had a primary tumor in both sides, and the primary tumor location was unknown in four patients (0.5%). Patients with a right-sided primary tumor were older and a higher proportion were female (42.5% versus 32.0%), compared with those with a left-sided primary tumor.
Overall survival significantly improved by adding SIRT with SIR-Spheres to first-line mFOLFOX6 chemotherapy (± bevacizumab) in metastatic colorectal cancer patients with a right-sided primary tumor (median 22.0 versus 17.1 months, with or without SIRT, respectively). No improvement in survival was seen from the addition of SIRT to first-line mFOLFOX6 chemotherapy for patients with left-sided primary tumors (median 24.6 versus 26.6 months, with or without SIRT).
A standard statistical test of treatment interaction by location for overall survival also proved highly significant (chi-square: 9.49, p = 0.002), providing further evidence that the observed benefit of adding SIRT to mFOLFOX6 chemotherapy in right-sided primary metastatic colorectal cancer patients was not a chance finding.
Patients with right-sided primary tumors treated with SIRT plus mFOLFOX6 also showed a trend toward improved progression-free survival, compared with those who received mFOLFOX6 alone (median 10.8 versus 8.7 months), according to the researchers.
There were no significant differences in the incidence of adverse events between patients with right-sided primary tumors and those with left-sided primary tumors.
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