Oncologists treat people who have been diagnosed with cancer. Patients are treated by oncologists in conjunction with other specialists within the branch of medicine related to the type of cancer they have been diagnosed with.

From the diagnosis of cancer through the development of the disease and its termination, oncologists are responsible for the care of cancer patients. Their services include providing information on everything from the type of cancer to the stage of the disease and its location. It is common to use a multidisciplinary team of oncologists for cancer treatment due to the variety of methods used, which range from surgery to chemotherapy and radiation therapy. There are many specialists who provide cancer care, including pathologists, diagnostic radiologists, and nurse practitioners.

Oncology includes the branches of medical oncology, surgical oncology, and radiation oncology. An oncologist provides cancer treatment, such as chemotherapy and/or medications. The role of surgical oncologists is to remove tumors, to remove tissue, as well as to perform surgical biopsies. Radon oncologists use radiation to treat cancer. A pediatric oncologist, as well as a gynecologic oncologist, are two other main types of oncologists.

Hematologists specialize in diagnosing and treating cancers of the blood, including leukemia, lymphomas, and myelomas. A hematologist studies diseases of the blood and blood vessels.

Oncologists provide cancer patients with a wide range of treatments including chemotherapy, radiotherapy, diet advice, oral medication, anticoagulation therapy, intramuscular injections, blood transfusions, venesection, and bone marrow transplants.