Hematology is the subspecialty of internal medicine concerned with disorders of the blood and blood-forming organs. Oncology is a subspecialty of internal medicine that focuses on medical treatment of cancer. Because cancers of blood-forming cells were the first for which reasonably effective chemotherapy was developed, hematology and oncology have often been linked, although now many oncologists are not hematologists. Radiation oncology is a subspecialty of radiology that focuses on providing radiation therapy to cancer patients. Also, certain surgeons specialize in the treatment of cancer. Regardless of the branch of medicine to which they belong, cancer specialists work together to ensure a comprehensive approach to treatment for each patient.