Medical Oncology is an internal medicine sub-branch dealing with treatment of cancer by drugs and research of cancer medicines. Although chemotherapy has a great importance in treatments of cancer by drugs, it is not the only method. Treatments related to cancer such as; hormone-regulating drugs, targeted drugs, and drugs which are effective on immune system in addition to chemotherapy are used in medical oncology.

A closely collaboration with the other specialties such as; radiation oncology, surgery, nuclear medicine, radiology, pathology is required during the implementations of medical oncology. The best results of cancer treatments are acquired by multidisciplinary studies in this way.

The drugs’, which are used in oncology, dosage which is effective in treatment and the dosage which may be fatal are very close to each other. For this reason, the doctors, who perform the treatment, should know side effects of these drugs very well. The patient who responds the treatment may be lost due to treatment toxicity. Therefore, the doctor should be in a good communication with the patient and the relatives of the patient in the treatment period.

Stating of the cancers, methods of surgical intervention and types of the drugs changes in time. Therefore, the doctors dealing with oncology should closely follow these developments. It is now recognized that common cancers such as; lung, breast, colon have sub-groups and each of them should be treated by separated methods. For example; while the drug called as trastuzumab is very effective for both 2 positive breast cancer, it is useless for both 2 negative breast cancers.

Biopsy and pathologic evaluation should be performed before the treatment of cancers begin and after the disease is staged by imaging methods, treatment program (surgery, radiotherapy, chemotherapy, hormone drugs, targeted therapies) should be prepared. While medical oncology becomes part of treatment mostly in post-operative period (adjuvant applications), it may begin to treatment in pre-operative period (neoadjuvant applications). In the advanced cancers (breast, colon, lung), the effect of surgery can be increased in pre-operative implementations. Although oncologic implementations have general principles, the best approach is to evaluate patients with different specialties and determine the best special treatment method for the patient even in the diagnosis stage.