Dr. Alyson Haslam of the Department of Epidemiology and Biostatistics, University of California San Francisco in San Francisco, CA, US and colleagues reported on 12 April 2021 in the Annals of Oncology that the percentage of patients with cancer in US who are eligible for and respond to genome-targeted therapy has increased over time. However, the percentage of patients who responded to genome-targeted therapy was modest with estimation of increase from 2.73% in 2006 to 7.04% in 2020. Most of the increase in response was seen prior to 2018, and most of the increase in eligibility after 2018.
The authors reported in the study background that prior studies have evaluated the percentage of patients with advanced or metastatic cancer who are eligible for and respond to this class of medications. However, the number of FDA approvals for drugs targeting genomic indications has grown rapidly. Therefore, they sought to update the estimates of both eligibility for and response to genome-targeted therapies that have been approved by US Food and Drug Administration (FDA) to reflect estimates as of 2020.
They calculated these estimates for both genome-targeted drugs and genome-informed therapies. They defined genome-targeted drugs as those approved for use based on findings of a genomic test where the drug targets the aberration detected by that test. They defined genome-informed therapies as any drug given after a genomic test, including all genome-targeted drugs, regardless of whether the drug was meant to target the abnormalities found in the test or acted via an alternative mechanism of action.
For each drug approved by FDA, they abstracted the date approved, the indication, the tumour type, the genomic indication, and the response rate. They used mortality data from the American Cancer Society to estimate eligibility for these drugs, based on prevalence statistics from the published literature. They then multiplied eligibility by the response rate in the FDA label to generate an estimate for the percentage of patients with cancer in US who respond.
They identified 72 unique approvals for 51 different drugs that were approved for 36 genomic indications for 18 cancer types from January 2006 through June 2020.
For genome-targeted therapy, estimated eligibility was 5.13% in 2006, increased to 8.82% by the end of 2018, and has since increased to 13.60% in 2020. For genome-informed therapy, estimated eligibility was 10.70% in 2006, 16.54% in 2018, and 27.30% in 2020.
For genome-targeted therapy, estimated response was 2.73% in 2006, increased to 5.48% by the end of 2018, and has since increased to 7.04% in 2020. For genome-informed therapy, estimated response was 3.33% in 2006, 7.68% in 2018, and 11.10% in 2020.
These estimates were based on both the prevalence of disease and the prevalence of mutation for the respective cancer type.
The median duration of response reported in the FDA approval notifications for genome-targeted therapy was 18.9 months (range, 5.7 months to 80 months) in 2006 and 17.6 months (range, 4.6 months to 80 months) in 2020. The median response rate was 19.0% (range, 10.6% to 95.3%) in 2006 and 63.5% (range, 12% to 95.3%) in 2020.
The authors acknowledged that there are several limitations in their analysis.
They concluded that most of the increase in eligibility for genome-targeted therapies was seen after 2018, whereas most of the increase in response was seen prior to 2018.
The study was funded by Laura and John Arnold Foundation.
Haslam A. Kim MS, Prasad V. Updated estimates of eligibility for and response to genome-targeted oncology drugs among US cancer patients, 2006-2020. Annals of Oncology; Published online 12 April 2021. DOI: https://doi.org/10.1016/j.annonc.2021.04.003