Larotrectinib versus historical standard of care in patients with infantile fibrosarcoma: protocol of EPI-VITRAKVI.

The EPI VITRAKVI study is a retrospective study designed to place the results of the single-arm Phase I/II larotrectinib SCOUT trial into context by comparison with external historical controls. Its primary objective is to compare the time to medical treatment failure between larotrectinib and the historical standard of care (chemotherapy) in patients with infantile fibrosarcoma. External historical cohorts have been selected by using objective criteria. The Inverse Probability of Treatment Weighting method will be used to adjust for potential confounding. The current publication illustrates how an external control arm study can complement data from a single-arm trial and addresses uncertainties encountered in the assessment of therapies targeting rare abnormalities where randomized controlled trials are considered not feasible. Clinical Trial Registration: NCT05236257 (ClinicalTrials.gov). Infantile fibrosarcoma (IFS) is a rare type of childhood cancer that commonly affects the legs and arms. In IFS cancers, the units which carry the information that determines your traits (genes), typically have specific changes which leads to the creation of an altered fusion protein, a protein which is created by joining parts of two different genes. This altered fusion protein can cause cancer cells to survive and to grow. Larotrectinib works by blocking the altered fusion protein and is already available in Europe and in many other countries. It is approved for prescription to patients with the altered fusion protein, whose cancer has spread to nearby tissues and/or lymph nodes or to other parts of the body. Since IFSs a rare disease, previous studies did not compare larotrectinib with the standard of care, which is chemotherapy. The main purpose of our study is to collect more results on how well larotrectinib works compared with chemotherapy taken from real world evidence data. The present publication explains how such a comparison can be made and how such a study can help in the assessment of treatments that target rare diseases.