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 12,580 practicing oncologists. Broken out by state, oncology doctor density in Alabama is 135, in Alaska is 13, in Arizona is 176, in Arkansas is 90, in California is 1,224, in Colorado is 172, in Connecticut is 203, in Delaware is 30, in District of Columbia is 85, in Florida is 719, in Georgia is 304, in Hawaii is 37, in Idaho is 43, in Illinois is 537, in Indiana is 252, in Iowa is 105, in Kansas is 110, in Kentucky is 147, in Louisiana is 150, in Maine is 58, in Maryland is 373, in Massachusetts is 554, in Michigan is 427, in Minnesota is 281, in Mississippi is 96, in Missouri is 248, in Montana is 33, in Nebraska is 78, in Nevada is 59, in New Hampshire is 65, in New Jersey is 368, in New Mexico is 77, in New York is 1,164, in North Carolina is 342, in North Dakota is 38, in Ohio is 459, in Oklahoma is 106, in Oregon is 141, in Pennsylvania is 665, in Rhode Island is 60, in South Carolina is 139, in South Dakota is 22, in Tennessee is 278, in Texas is 868, in Utah is 54, in Vermont is 32, in Virginia is 258, in Washington is 309, in West Virginia is 75, in Wisconsin is 246, and in Wyoming is 16.