Oncology (from the Ancient Greek onkos (ὄγκος), meaning bulk, mass, or tumor, and the suffix -logy (-λογία), meaning "study of") is a branch of medicine that deals with cancer. A medical professional who practices oncology is an oncologist.
Oncology is concerned with:
The diagnosis of any cancer in a person
Therapy (e.g. surgery, chemotherapy, radiotherapy and other modalities)
Follow-up of cancer patients after successful treatment
Palliative care of patients with terminal malignancies
Ethical questions surrounding cancer care
Screening efforts:
of populations, or
of the relatives of patients (in types of cancer that are thought to have a hereditary basis, such as breast cancer)