Many new cancer drugs require updated safety labels

Many serious or potentially fatal adverse reactions associated with new, targeted anticancer agents are not reported in the original published research on the drug, and they are not known to oncologists until years later when updated drug labels, including boxed warnings, are required, according to research published online in the Journal of Clinical Oncology, HealthDay News reported.

Researchers conducted a review of 12 targeted anticancer agents with updated drug labels because of safety concerns and 36 corresponding randomized controlled trials (RCTs) referenced in the updated labels. In the updated drug labels, there were 76 serious adverse drug reactions (ADRs) reported - half of which were potentially fatal. Researchers found that the corresponding RCTs for the targeted anticancer agents did not describe 39% of serious ADRs and 39% of potentially fatal ADRs, and the initial drug label did not describe 49% of serious ADRs and 58% of potentially fatal ADRs.

Doctors need to recognize that many drugs have serious side effects that are not evident from the clinical trials that led to their approval, which is the main source of their information, Ian Tannock, MD, one of the study’s researchers and a professor of medical oncology at Princess Margaret Hospital and the University of Toronto, told Formulary. “This is particularly true when [doctors] use new drugs in patients with other medical problems,” he said. “Such people are often excluded from the trials.”