Plain language summary of the THOR Cohort 1 study comparing treatment with erdafitinib or chemotherapy in advanced or metastatic urothelial cancer

What is this summary about? This is a plain language summary of an article published in The New England Journal of Medicine in 2023 describing results from Cohort 1 of the THOR study. Participants had advanced or metastatic unresectable urothelial cancer with certain characteristics. Participants’ cancer must have certain genetic alterations in 1 or both of 2 related genes named fibroblast growth factor receptor 2 (FGFR2) and 3 (FGFR3). The cancer must have grown or spread after participants received 1 or 2 previous cancer treatments that included an immunotherapy medication. Additional effective treatment options are needed for people after immunotherapy. What were the results of the study? The median overall survival was 12.1 months for erdafitinib versus 7.8 months for chemotherapy. In the erdafitinib group, an estimated 85% of participants were still alive at 6 months and an estimated 51% were still alive after 12 months. The median progression-free survival was 5.6 months for participants treated with erdafitinib versus 2.7 months for those treated with chemotherapy. The objective response rate was 45.6% in the erdafitinib group and 11.5% in the chemotherapy group. Common side effects of erdafitinib were manageable and included high phosphate levels in the blood (hyperphosphatemia), diarrhea, an inflamed and sore mouth, and nail disorders. What do the results of the study mean: The THOR Cohort 1 study found that treatment with erdafitinib extended the amount of time that participants were alive compared with chemotherapy treatment. After a pre-planned analysis determined that participants had better outcomes with erdafitinib, those receiving chemotherapy were allowed to switch to erdafitinib. Based on these results, erdafitinib was approved by the US Food and Drug Administration (FDA) for adults with advanced or metastatic urothelial cancer with certain FGFR3 gene alterations whose cancer continued to grow after at least 1 previous systemic treatment, including chemotherapy/immunotherapy. Erdafitinib is also approved in other countries to treat advanced or metastatic urothelial cancer; please check with your doctor for more details.