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  1. Spotlight on CDER Science

The Role of Disclosures: Helping to Understand Oncology Clinical Trial Endpoints

FDA Research Focused on Direct-to-Consumer Television Advertising

Clinical endpoints are measurable events or outcomes that can help determine whether a medical intervention, such as a therapy, is benefiting patients. In oncology, clinical endpoints can help assess the safety and effectiveness of new cancer treatments. The overall survival endpoint is generally defined as the average length of time patients are alive after the start of treatment.1 Overall survival is usually considered the “gold standard” (or ideal) primary endpoint in oncology because patients with cancer often want to take medications that can help them live longer. 

However, showing an overall survival advantage in a clinical trial can be lengthy, costly and otherwise challenging.2 For that reason, researchers use other clinical endpoints to show patient benefit — and FDA may approve drugs based on these endpoints. Two common oncology endpoints are overall response rate and progression-free survival. The overall response rate1 is the proportion of patients whose cancer shrinks or disappears after treatment; progression-free survival1 is the average length of time after the start of treatment in which a person is alive, and their cancer does not grow or spread. 

It is important that patients and their caregivers understand these endpoints, so that they can make the most informed treatment decisions. However, researchers have found that patients with cancer can misinterpret them, often confusing other endpoints with overall survival. As a result, patients may expect a therapy to help them live longer — and may accept more associated risks — when the medication has not been proven to do so. At the same time, research has suggested that disclosures can help consumers stop conflating overall survival with other endpoints. These disclosures specifically state that the drug has not yet been shown to increase survival. 

If patients are in a clinical setting, like a doctor’s office, they may be able to ask clarifying questions about clinical endpoints associated with medications. However, people may also learn about prescription oncology drugs through direct-to-consumer (DTC) television advertising, where there is not an opportunity for interactive discussion about the clinical endpoint claims presented in the ads.  

The Goal of the Study 

FDA researchers wanted to see whether consumers understand oncology endpoints in DTC television ads, and whether disclosures can help people distinguish among overall survival, overall response rate, and progression-free survival. To that end, FDA researchers conducted two studies that examined a television ad for fictional prescription oncology drugs: Xedaliti for lung cancer and Vulpafen for multiple myeloma3.  In each study, participants were randomly assigned to watch one of five television ads: an ad with an overall survival claim; ads with an overall response rate claim with and without a disclosure; and ads with a progression-free survival claim with and without a disclosure. 

The researchers recruited American adults in the general population, making sure at least 25 percent of participants in each cohort had low health literacy. After participants watched the ad, they completed a survey that included open-ended questions (questions that encourage a full answer); true/false questions; and questions about the extent to which the ad affected their perceptions and intentions.  

Research Findings 

In the open-ended responses, participants correctly described (and differentiated among) the three endpoints. However, when researchers asked participants whether the drug can help people live longer, subjects did not differentiate progression-free survival and overall response rate from overall survival when there was no disclosure. 

In the lung cancer study, 90 percent of participants who watched the ad with the overall response rate claim without a disclosure thought the drug would help people live longer, compared with 30 percent of participants who watched the ad with a disclosure. Among people in the progression-free survival ad group without a disclosure, 93 percent of people thought the drug would help people live longer; among the group with a disclosure, this number dropped to 51 percent. Similar data trends exist for the multiple myeloma study.

When researchers asked about the disclosure specifically, they found that participants noticed it and understood its purpose. Across the studies, approximately 60 to 70 percent of participants who saw an ad with a disclosure understood that the drug’s effect on overall survival is currently unknown.

The Role of Disclosures  

From this study, we can conclude that although participants in the different groups understood the three endpoints and could differentiate among them, people still made inaccurate inferences. The findings show that people may be overly optimistic when they see ads with claims about overall response rate and progression-free survival without a disclosure stating that the drug has not yet been shown to extend life. The findings align with previous studies, which have found that disclosures may convey important information, help correct potential misunderstandings and manage expectations about a drug’s benefits. 

1 US FDA. Patient-Friendly Language for Cancer Clinical Trials. Accessed May 15, 2023. 
2 Delgado A, Guddati AK. Clinical endpoints in oncology-a primer. American Journal of Cancer Research. 2021, 1121-1131. PMC8085844.
3 Sullivan HW, O-Donoghue AC, Boudewyns V, et al. Patient understanding of oncology clinical trial endpoints in direct-to-consumer television advertising. The Oncologist. 2023. 1-12. doi: 10.1093/oncolo/oyad064

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