Factors contributing to poorer clinical outcomes in adults compared with children include the following: Less ability to tolerate intensive chemotherapy More frequent and severe comorbidities Higher risk ALL genetics that confer chemotherapy resistance Poorer adherence to ALL treatment regimens, which include frequent (often daily or weekly) out-patient chemotherapy and doctor visits Less frequent use of pediatric-inspired treatment regimens Most investigatory protocols select patients with poor prognostic factors for more intense therapy because the increased risk of and toxicity from treatment are outweighed by the greater risk of treatment failure leading to death.