What does an oncologist (cancer doctor) do?
An oncologist is a doctor who diagnoses and treats cancer. They plan treatment such as chemotherapy, immunotherapy, or radiation, and follow you afterward.
Last updated November 11, 2026
Find oncologists (cancer doctors) near you
When people see one
- A biopsy or scan shows cancer
- Your doctor finds a suspicious mass or abnormal blood test
- You have a past cancer and need follow-up care
- You want a second opinion on a cancer treatment plan
How it differs
General surgeon: A surgeon removes tumors. An oncologist plans medical treatment and coordinates care, often alongside the surgeon.
On 2027 Colorado plans
Do you need a referral? On some plans. 37 of the 148 2027 plans need a referral from your primary care provider to see a specialist: Kaiser Permanente's 29 plans (you may self-refer to certain specialists) and Denver Health (Elevate)'s 8 plans (self-referral allowed for OB-GYN and outpatient mental health care). The other 111 don't, according to each plan's 2027 summary of benefits. Confirm in the plan's summary of benefits.
What a visit costs (the plan's filed "Specialist Visit" benefit, in network, before any extra savings on silver plans):
- Bronze: $100 to $140 a visit on 10 of 56 plans; on the other 46, you pay toward your deductible or a share of the bill.
- Silver: $50 to $90 a visit on 44 of 58 plans; on the other 14, you pay toward your deductible or a share of the bill.
- Gold: $50 to $90 a visit on 26 of 30 plans; on the other 4, you pay toward your deductible or a share of the bill.
In-network care costs less. Out-of-network visits on an HMO or EPO usually aren't covered except in an emergency.
In Colorado
Public records list 336 oncologists (cancer doctors) at 144 Colorado locations.
- Denver County: 28 locations
- Adams County: 15 locations
- El Paso County: 14 locations
- Douglas County: 12 locations
- Arapahoe County: 11 locations
- Boulder County: 9 locations
Counties with the fewest: Summit (1), Rio Blanco (1), Phillips (1), Morgan (1), Moffat (1). 37 counties have none.
Questions to ask the office
- Do I need a referral from my primary care doctor?
- Which 2027 plans and network names do you take?
- Where are treatments given, and is that facility in my network?
- Are the drugs billed through the clinic or a specialty pharmacy?