Oncology is the study and treatment of cancer and tumors. An oncologist is a physician who diagnoses and treats cancer patients. The oncologist sometimes uses chemotherapy, and consults with other physicians to coordinate other methods of cancer treatments for a patient. Cancer patients need to take in to account the likelihood of a cure, or of prolonging life when cure is not possible, the effect of treatment on their symptoms, and the side effects of the treatment. People who are candidates for radiation therapy or anti-cancer drugs need to understand the risks involved with treatment. An oncologist can help to counsel a patient on treatment options and what to expect.

Physicians in this specialty treat patients suffering from numerous diseases and illnesses, but some of the most common are colon cancer, breast disease, spinal cord tumors, melanoma, skin cancer, breast cancer, bone marrow, hodgkin's disease, lymphoma, mesothelioma, sarcoma, lung cancer, leukemia, pancreatic cancer, cervical cancer, liver cancer, mesothelioma cancer (asbestos cancer), brain cancer, acute myeloid leukemia, and bone cancer.

Once properly diagnosed, practitioners can perform numerous procedures on patients including colonoscopy, breast reconstruction, chemotherapy, brachytherapy, cryosurgery, mastectomy, cryotherapy, cabg, breast surgery, surgery, radiotherapy, bone marrow transplantation (bmt), adjuvant therapy, monoclonal antibody treatments, external beam radiotherapy, hormone manipulation, and immunotherapies.

To diagnose patients with possible illnesses and diseases, specialists will often perform one of many tests including biopsy, mri scanning, beta- hcg, ct scanning, x-rays, magnetic resonance imaging (mri), computed axial tomography (ct or cat scan), ultrasound, endoscopy, nse, cea, blood tests, ca 125, tumor markers, beta hcg, positron emission tomography, scintigraphy, psa, and alpha fetoprotein.

Doctor density varies by specialty and location. The United States has 9,894 practicing oncologists. Broken out by state, oncology doctor density in Alabama is 103, in Alaska is 5, in Arizona is 138, in Arkansas is 66, in California is 996, in Colorado is 135, in Connecticut is 180, in Delaware is 23, in District of Columbia is 56, in Florida is 579, in Georgia is 226, in Hawaii is 27, in Idaho is 28, in Illinois is 430, in Indiana is 194, in Iowa is 76, in Kansas is 90, in Kentucky is 116, in Louisiana is 124, in Maine is 45, in Maryland is 328, in Massachusetts is 473, in Michigan is 325, in Minnesota is 212, in Mississippi is 75, in Missouri is 216, in Montana is 33, in Nebraska is 53, in Nevada is 48, in New Hampshire is 41, in New Jersey is 289, in New Mexico is 60, in New York is 939, in North Carolina is 251, in North Dakota is 33, in Ohio is 364, in Oklahoma is 68, in Oregon is 104, in Pennsylvania is 498, in Rhode Island is 49, in South Carolina is 115, in South Dakota is 14, in Tennessee is 210, in Texas is 769, in Utah is 44, in Vermont is 19, in Virginia is 195, in Washington is 261, in West Virginia is 56, in Wisconsin is 192, and in Wyoming is 12.