FDA Uncertainties About Cancer Drugs Largely Missing from Medical Literature and Guidelines
Key Insights
A new study reveals that more than 75% of FDA-identified uncertainties about cancer (search) drugs approved between 2019-2022 were not communicated in pivotal trial publications or NCCN (search) guidelines.
Medical journals published only 22% of FDA uncertainties while NCCN (search) guidelines reported just 23%, with over half of publications and guidelines reporting no FDA uncertainties at all.
The most common uncertainties identified by FDA reviewers included concerns about long-term benefits and harms, single-arm trial designs, benefit-risk balance, and generalizability of trial data.
A comprehensive analysis of FDA cancer (search) drug approvals has revealed a significant communication gap between regulatory reviewers and clinical practice, with more than three-quarters of FDA-identified uncertainties about new cancer treatments failing to reach the medical literature or treatment guidelines that guide oncologists' prescribing decisions.
The study, published in Health Affairs and led by researchers from Harvard Medical School and the London School of Economics (search), examined 48 cancer (search) drugs approved by the FDA between 2019 and 2022 that had pivotal trials published in medical journals and were referenced in National Comprehensive Cancer Network (search) (NCCN (search)) guidelines.
Widespread Omission of Critical Information
FDA reviewers identified uncertainties about 79.2% of the 48 drugs evaluated, totaling 94 important uncertainties that were considered crucial to approval decisions. However, medical journals published only 22% of these uncertainties, while NCCN (search) guidelines reported just 23%. Strikingly, 53% of journal publications and 47% of guidelines reported no FDA uncertainties at all.
"Clearly there's some sort of disconnect that's happening here in the approval process," said Avi Cherla, MSc, a research fellow in the department of population medicine at Harvard Medical School and lead author of the study.
The most common uncertainties identified by FDA reviewers included concerns about long-term benefits and harms (24.4%), single-arm trial design (23.4%), benefit-risk balance (17%), and generalizability (8.5%).
Beyond Study Limitations
The researchers emphasized that uncertainties differ from commonly reported study limitations. While a single-arm trial represents a limitation in study design, the uncertainty it creates involves the lack of comparative data and variability in treatment effects that extend beyond the design itself.
"A single-arm trial is a limitation. It's not a randomized trial," Cherla explained. "The uncertainty that this creates is that we don't have comparative data, we're not sure about the treatment effect because it could be more variable. There are many other issues that this creates that are beyond just the study design."
Impact on Clinical Decision-Making
The findings are particularly concerning given that more than 75% of cancer (search) drugs receive FDA approval through expedited programs designed to accelerate patient access to treatments. With 80% of today's cancer drugs reaching the US market under the FDA's accelerated approval pathway, these communication gaps may significantly impact clinical decision-making.
"If you don't know about a significant uncertainty with a drug, that could realistically make you overestimate the benefits of the drug or even underestimate its risks," Cherla noted. "Without knowing about these key uncertainties, you can't really make informed decisions."
Regulatory Documentation vs. Clinical Communication
The research builds on previous work showing that FDA drug labels, the agency's primary communication tool with physicians, included only 26% of all FDA-identified uncertainties and 48% of those deemed important to approval decisions for 52 cancer (search) drugs approved from 2019 through 2022.
FDA reviewers routinely identify uncertainties during the approval process, which represent evaluations of benefits versus risks that cannot be fully answered during clinical trials. These may arise from study population characteristics, trial duration, data analysis concerns, missing outcome data, or selection of reported results.
Guidelines Performance Below Expectations
The researchers found that NCCN (search) guidelines, widely considered the gold standard by clinicians, performed no better than journal publications in communicating FDA uncertainties. Among the drugs evaluated, NCCN guidelines recommended 37% with category 1 high levels of evidence and 58% with category 2A recommendations.
Notably, drugs that NCCN (search) guidelines did not recommend had the highest mean number of FDA uncertainties listed, suggesting some correlation between uncertainty levels and recommendation strength.
Barriers to Communication
Several factors may contribute to the poor communication of uncertainties. Journals and guideline developers lack access to participant-level trial data that enables FDA reviewers to conduct independent analyses. However, researchers noted that many uncertainties could have been identified without such detailed access.
Word count limitations in journal publications may also play a role, though this explanation falls short for guidelines that span hundreds of pages without such constraints.
Call for Improved Transparency
The researchers called for the FDA to make its benefit-risk assessments more accessible and for guidelines to more routinely include uncertainties in their recommendations. They suggested that current communication mechanisms may be inadequate, particularly for drugs approved through expedited pathways.
"There does not seem to be an adequate mechanism in place to adequately communicate the known evidence and limitations of drugs to physicians, especially for drugs approved through expedited pathways," Cherla stated.
The study's findings highlight a critical gap in the translation of regulatory knowledge to clinical practice, potentially affecting treatment decisions for cancer (search) patients at a time when novel therapies are entering the market at an unprecedented pace.