Indeed, PFS was more than double in the trial group assigned to vandetanib compared with those assigned to placebo, report the researchers in The Lancet Oncology.
However, a greater number of patients in the vandetanib group developed adverse events after taking the drug versus those who took placebo, and two individuals died from treatment-related causes in the drug group compared with one in the placebo group.
Current therapies are largely ineffective in this group of patients, write Martin Schlumberger (Université Paris-Sud, France) and team who believe that vandetanib is "the first targeted agent to demonstrate improved PFS in patients with locally advanced cancer in a randomized phase II study."
After a median follow up of 18.9 months, 113 of 145 thyroid cancer patients in the study had disease progression, measured using the Response Evaluation Criteria in Solid Tumors (RECIST), of whom 52 were assigned to once-daily oral vandetanib 300 mg, and 61 to placebo, report the researchers.
The median PFS was significantly longer in those who received the study drug compared with those who did not, at 11.1 versus 5.9 months.
Rates of adverse events leading to discontinuation of treatment, and rates of grade 3 or worse (according to US National Cancer Institute Common Terminology Criteria for Adverse Events) events were higher among patients who took vandetanib compared with placebo, and common events that occurred in the former group with a frequency of more than 10% were diarrhea, hypertension, and acne.
However, the authors note that none of these safety concerns were new compared with other studies of vandetanib in cancer patients. Furthermore, they remark that: "Incidence of diarrhea and rash are consistent with pharmacodynamic inhibition of EGFR [epidermal growth factor receptor] signaling with vandetanib and... were manageable by standard medical care."
The two deaths in the vandetanib group were a result of hemorrhage from skin metastases and pneumonia, and the death in the placebo group was attributed to pneumonia.
While "substantial" PFS would benefit patients with thyroid cancer, "meaningful assessment of PFS needs a randomized phase III study," the research team concludes.
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