Observational studies and clinical trials in hematology aim to examine an array of treatments for blood disorders including chemotherapy, radiation therapy, hematopoietic cell transplantation, and, more recently, targeted treatments, gene therapy and immunotherapy. The latter includes chimeric antigen receptor-T cell (CAR T) therapy and immunomodulating drugs. Some treatment modalities are more common in patients diagnosed with non-malignant hematologic disorders while others are frequently used to treat malignant diseases. The relevant outcomes being studied must address the goals of the study and provide meaningful information to physicians, patients, and policymakers. The outcomes that are reported ought to reflect treatment course, disease progression, survival and reflect patients’ social, emotional and functional well-being [1]. Endpoints are the specific measures of these outcomes, and much consideration should be given to their selection.

Hematologic malignancies such as leukemia, lymphoma, and multiple myeloma pose an imminent threat to a patient's life. The goals of the treatment for hematologic malignancies include cure (whenever possible), achieving and prolonging remission, treating existing symptoms, preventing complications, and improving patients' quality of life. Most non-malignant hematologic diseases are not life-threatening, but they may cause symptoms such as fatigue, pain, infections, and blood loss. Treatments for such diseases are often aimed at the reduction of these symptoms.

In this review, we describe the clinical endpoints frequently used in studying hematologic diseases and provide general guidelines for their statistical analysis. Clinical endpoints are often used in establishing treatment safety and efficacy. Non-clinical endpoints such as biomarkers and their correlation to clinical outcomes may be harder for the patients to understand. Nevertheless, non-clinical endpoints are also associated with disease manifestation and may influence treatment targets and decision making [1]. While some outcomes studied are common across malignant and non-malignant hematologic studies (e.g., survival and patient reported outcomes), others are disease or treatment specific (e.g., neurologic toxicity after CAR T cell therapy). We also briefly discuss composite and surrogate endpoints along with considerations for choosing primary and secondary endpoints in a clinical trial design framework.