Oncology is a branch of medicine that deals with the study, treatment, diagnosis and prevention of cancer. A medical professional who practices oncology is an oncologist.

Oncology is concerned with:

• The diagnosis of any cancer in a person (pathology)
• 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 

 Diagnosis:

Medical histories remain an important screening tool: the character of the complaints and nonspecific symptoms (such as fatigue, weight loss, unexplained anemia, fever of unknown origin, paraneoplastic phenomena and other signs) may warrant further investigation for malignancy.

Therapy:
Depending upon the cancer identified, followup and palliative care will be administered at that time. Certain disorders (such as ALL or AML) will require immediate admission and chemotherapy, while others will be followed up with regular physical examination and blood tests.

Often, surgery is attempted to remove a tumor entirely. This is only feasible when there is some degree of certainty that the tumor can in fact be removed. When it is certain that parts will remain, curative surgery is often impossible, e.g. when there are metastases elsewhere, or when the tumor has invaded a structure that cannot be operated upon without risking the patient’s life. Occasionally surgery can improve survival even if not all tumour tissue has been removed; the procedure is referred to as “debulking” (i.e. reducing the overall amount of tumour tissue). Surgery is also used for the palliative treatment of some of cancers, e.g. to relieve biliary obstruction, or to relieve the problems associated with some cerebral tumors. The risks of surgery must be weighed against the benefits.