The purpose of this study is to evaluate the investigational oral drug AMXT 1501 in combination with oral eflornithine (DFMO). An investigational drug is one that has not been approved by the U.S. Food \& Drug Administration (FDA), or any other regulatory authorities around the world for use alone or in combination with any drug, for the condition or illness it is being used to treat.

The goals of this part of the study are:

* Establish a recommended dose of AMXT 1501 in combination with DFMO
* Test the safety and tolerability of AMXT 1501 in combination with DFMO
* To determine the activity of study treatments chosen based on:
* How each subject responds to the study treatment
* How long a subject lives without their disease returning/progressing

The purpose of this study is to evaluate the efficacy of digoxin in treating relapsed non-SHH, non-WNT medulloblastoma in pediatric and young adult patients.

This ComboMATCH patient screening trial is the gateway to a coordinated set of clinical trials to study cancer treatment directed by genetic testing. Patients with solid tumors that have spread to nearby tissue or lymph nodes (locally advanced) or have spread to other places in the body (advanced) and have progressed on at least one line of standard systemic therapy or have no standard treatment that has been shown to prolong overall survival may be candidates for these trials. Genetic tests look at the unique genetic material (genes) of patients' tumor cells. Patients with some genetic changes or abnormalities (mutations) may benefit from treatment that targets that particular genetic mutation. ComboMATCH is designed to match patients to a treatment that may work to control their tumor and may help doctors plan better treatment for patients with locally advanced or advanced solid tumors.

This phase III trial compares the effectiveness of fractionated stereotactic radiosurgery (FSRS) to usual care stereotactic radiosurgery (SRS) in treating patients with cancer that has spread from where it first started to the brain. Radiation therapy uses high energy x-rays to kill tumor cells and shrink tumors. FSRS delivers a high dose of radiation to the tumor over 3 treatments. SRS is a type of external radiation therapy that uses special equipment to position the patient and precisely give a single large dose of radiation to a tumor. FSRS may be more effective compared to SRS in treating patients with cancer that has spread to the brain.

The purpose of the study is to evaluate the safety and survival of carmustine wafers and radiation and retifanlimab with or without temozolomide (TMZ) in newly-diagnosed adult subjects with glioblastoma multiform after carmustine wafer placement.