Patients with metastatic pancreatic ductal cancer survived a median of 7.9 months after receiving multiple cycles of an investigational radioimmunotherapy agent plus gemcitabine, but only 3.4 months when they received radioimmunotherapy alone, according to a randomized phase Ib clinical trial.
Toxicity consisted mainly of low platelet counts and other cytopenias, said Dr. Vincent J. Picozzi Jr. speaking at a press briefing prior to a pancreatic cancer conference held by the American Association for Cancer Research in New Orleans. There was little evidence of increased infection or bleeding, he said.
Dr. Vincent Picozzi
The investigational radioimmunotherapy agent used in the trial, 90Y-clivatuzumab tetraxetan, is designed to specifically target pancreatic cancer cells throughout the body, said Dr. Picozzi, director of the Pancreas Center of Excellence at the Virginia Mason Medical Center’s Digestive Disease Institute, Seattle. The agent links a radioactive compound to an antibody that binds the MUC5ac protein, which is expressed on the surface of most pancreatic cancer cells, Dr. Picozzi said.
To test the safety and efficacy of the agent, the researchers enrolled 58 adults with metastatic pancreatic ductal cancer who had received at least two prior forms of treatment. All patients received 6.5 mCi/m2 90Y-clivatuzumab tetraxetan for 3 weeks, given in multiple smaller doses. Half the patients then received low-dose gemcitabine for 1 week, followed by 3 weeks of low-dose gemcitabine plus additional radioimmunotherapy with 90Y-clivatuzumab tetraxetan. Patients received up to nine treatment cycles, with 4-week intervals between cycles, Dr. Picozzi said.
In all, 53 patients completed at least one treatment cycle, and 23 completed at least two cycles. There were no infusion reactions, the investigators said. "Patients terminated treatment cycles due to disease progression or clinical deterioration, not treatment toxicity," Dr. Picozzi reported.
Overall survival for the entire cohort was similar between the two treatment arms. Using the Kaplan-Meier method, median overall survival (OS) was 3.9 months (range, 1.0-16.7 months) in the gemcitabine plus radioimmunotherapy arm, compared with 2.8 months (0.9-9.4 months) in the radioimmunotherapy-only arm (hazard ratio, 0.54; 95% confidence interval, 0.27-0.87; P = .020).
But among patients who completed multiple treatment cycles, median OS was 7.9 months in the gemcitabine arm, compared with only 3.4 months for the radioimmunotherapy-only arm (P = .004), Dr. Picozzi reported. Furthermore, three patients in the gemcitabine arm were still being observed 11 to 17 months after treatment.
"Patients who received two courses of treatment had a markedly improved survivorship – more than double that of patients who did not receive gemcitabine," Dr. Picozzi concluded, adding that a larger, randomized phase III trial is underway to confirm the results. "The trial is in the early stages at this point," he said. "It would be hard to anticipate results before 2015 or 2016."
Immunomedics Inc. funded the study. Dr. Picozzi declared no conflicts of interest.