Larotrectinib expanded access is for patients with cancer with a NTRK1, NTRK2, or NTRK3 gene fusion, who are ineligible for an ongoing larotrectinib clinical trial or have other considerations that prevent access to larotrectinib through an existing clinical trial. Gene fusion occurs when a gene is made by joining parts of two different genes. NTRK gene fusion can lead to the development of solid tumors in a variety of tissue types. The study drug larotrectinib blocks the action of the NTRK gene fusion. Expanded access is intended to treat individual patients with different types of cancers with a NTRK gene fusion who are unresponsive to current standard treatment for their condition and also are unable to participate in ongoing clinical trials.