This study evaluates immunologic response following COVID-19 vaccination in children, adolescents, and young adults with cancer. Vaccines work by stimulating the bodys immune cells to respond against a specific disease. The immune response produces protection from that disease. Effects from cancer and from treatments for cancer can reduce the bodys natural disease fighting ability (called immunity). Factors such as vaccine type, timing of vaccine dosing related to treatment for cancer and number of vaccine doses or boosts (extra vaccine shots) may strengthen or diminish the bodys protective immune response. This study may help researchers learn more about how the bodys immune system responds to the COVID-19 vaccine when the vaccination is given during or after cancer treatment.

This randomized clinical phase III trial studies how well web-based physical activity intervention works in improving long term health in children and adolescents with cancer. Regular physical activity after receiving treatment for cancer may help to maintain a healthy weight and improve energy levels and overall health.

This study aims to use clinical and biological characteristics of acute leukemias to screen for patient eligibility for available pediatric leukemia sub-trials. Testing bone marrow and blood from patients with leukemia that has come back after treatment or is difficult to treat may provide information about the patient's leukemia that is important when deciding how to best treat it, and may help doctors find better ways to diagnose and treat leukemia in children, adolescents, and young adults.

Difluoromethylornithine (DFMO) will be used in an open label, single agent, multicenter,
study for patients with neuroblastoma in remission. In this study subjects will receive 730
Days of oral difluoromethylornithine (DFMO) at a dose of 750 mg/m2 250 mg/m2 BID (strata 1,
2, 3, and 4) OR 2500 mg/m2 BID (stratum 1B) on each day of study. This study will focus on
the use of DFMO in high risk neuroblastoma patients that are in remission as a strategy to
prevent recurrence.