Medicare Coverage for Colorectal Cancer: Screening, Surgery, and Treatment

Colorectal cancer is the second leading cause of cancer death in the United States and the third most common cancer overall. Adults over 65 account for more than half of all new colorectal cancer diagnoses each year, making this squarely a Medicare-age disease. The good news: colorectal cancer caught early through screening is highly survivable — five-year survival rates exceed 90% for localized disease. And Medicare covers the full continuum of colorectal cancer care, from free preventive colonoscopy through surgery, chemotherapy, and the newest targeted biologics.

Understanding exactly what Part A, Part B, and Part D each cover — and what the cost-sharing looks like across different coverage options — helps Medicare beneficiaries make informed decisions about both care and insurance.

Colonoscopy Screening: Medicare’s No-Cost Preventive Benefit

A colonoscopy is the most powerful tool available for colorectal cancer prevention. Unlike other screening tests that detect cancer, colonoscopy can actually prevent cancer by finding and removing precancerous polyps before they progress. Medicare covers screening colonoscopies as a fully preventive benefit — no deductible, no coinsurance — under Part B.

Who Qualifies and How Often

Medicare covers screening colonoscopy at two different frequencies depending on your personal risk:

Average-risk adults: A screening colonoscopy is covered once every 10 years. Medicare does not set a minimum age for this benefit, but it applies to beneficiaries who have no personal history of polyps or colorectal cancer and no first-degree relatives diagnosed before age 60.

High-risk adults: Coverage increases to once every 2 years for beneficiaries with a higher-than-average risk of colorectal cancer. High-risk criteria include a personal history of colorectal cancer or adenomatous polyps, a first-degree relative (parent, sibling, child) with colorectal cancer or adenomatous polyps, or a family history of a hereditary colorectal cancer syndrome such as familial adenomatous polyposis (FAP) or Lynch syndrome.

Between a colonoscopy and the next one, Medicare also covers a flexible sigmoidoscopy (examination of the lower colon only) every 48 months — useful if a full colonoscopy isn’t possible or appropriate.

The 2023 “Polyp Billing Trap” Fix — and What Still Applies

For years, one of the most frustrating Medicare coverage issues was the “polyp billing trap”: a patient came in for a free preventive colonoscopy, a polyp was found and removed, and the colonoscopy was automatically rebilled from a preventive service to a diagnostic or therapeutic procedure — suddenly generating 20% coinsurance on what was supposed to be free care.

The Consolidated Appropriations Act of 2023 fixed this. Starting January 1, 2023, a colonoscopy that begins as a preventive screening stays covered as preventive — with no cost-sharing applied to the colonoscopy procedure itself — even if the physician removes polyps or takes biopsies during the same session.

What can still carry coinsurance:

• Anesthesia: Anesthesia services are billed separately from the colonoscopy by an anesthesiologist or CRNA. Anesthesia is not automatically preventive, and standard Part B 20% coinsurance applies to that portion.
• Pathology/laboratory fees: If removed polyps are sent to a lab for analysis, the pathology interpretation is billed separately and subject to standard Part B coinsurance.

These associated charges are typically modest — anesthesia and pathology for a routine colonoscopy rarely exceed a few hundred dollars combined — but they’re worth knowing about so you’re not surprised if you receive a bill.

If your colonoscopy is diagnostic (meaning you have symptoms — rectal bleeding, change in bowel habits, unexplained anemia, abdominal pain), the procedure is not a preventive service, and standard Part B cost-sharing applies: the annual Part B deductible ($283 in 2026) plus 20% coinsurance on the Medicare-approved rate.

Other Covered Colorectal Cancer Screening Tests

Colonoscopy is not the only option. Medicare covers several alternatives under Part B, all as preventive benefits with no cost-sharing:

Cologuard (stool DNA test): Cologuard, made by Exact Sciences, detects DNA markers and blood from colorectal cancer or precancerous polyps in a stool sample collected at home. Medicare covers Cologuard every 3 years for average-risk adults ages 45–75 who have no symptoms and no prior history of colorectal cancer, adenomatous polyps, inflammatory bowel disease, or high-risk conditions. The test is mailed to your home, completed privately, and mailed back — no bowel prep, no sedation, no time off work.

Fecal occult blood tests (FOBT/FIT): Guaiac-based (gFOBT) and immunochemical fecal occult blood tests (FIT) detect hidden blood in stool and are covered annually under Part B.

CT colonography (virtual colonoscopy): A CT scan of the entire colon, performed every 5 years for average-risk adults. No sedation required, though bowel prep still is. If CT colonography finds a polyp, a follow-up diagnostic colonoscopy is needed to remove it — that follow-up would have standard Part B cost-sharing.

For a detailed comparison of these tests and which Part B screenings are fully covered, see what Medicare Part B covers.

Diagnosis and Staging After a Positive Screening or Symptoms

When colorectal cancer is suspected or confirmed on biopsy, a full workup under Part B follows:

Imaging for staging: CT scan of the chest, abdomen, and pelvis (CT CAP) to evaluate for metastases. For rectal cancer specifically, pelvic MRI is the gold standard — it accurately defines how far the tumor has penetrated the rectal wall and whether lymph nodes are involved, guiding whether neoadjuvant (pre-surgery) radiation is needed. PET scan is covered under Part B for staging when CT or MRI findings are uncertain.

Blood tests: CEA (carcinoembryonic antigen) is covered under Part B as a tumor marker for colorectal cancer. It’s used for baseline staging and for surveillance after treatment.

Biomarker testing: Medicare covers comprehensive tumor genomic profiling for metastatic colorectal cancer. Key biomarkers that guide targeted therapy include RAS mutation status (KRAS and NRAS), BRAF V600E mutation status, MSI (microsatellite instability) or MMR (mismatch repair) status, HER2 amplification, and KRAS G12C mutation. These tests are covered under Part B as companion diagnostics for selecting targeted therapy — and getting the right targeted therapy can mean the difference between a regimen that works and one that doesn’t. See Medicare Part B vs. Part D drugs for how biomarker testing fits into the broader coverage framework.

Surgery Under Part A and Part B

Most colorectal cancer surgery is covered under Medicare Part A when it requires an inpatient hospital admission, or under Part B when performed as outpatient or ambulatory surgery.

Types of surgery covered:

• Right, left, or sigmoid colectomy: removal of the affected segment of colon. Laparoscopic approach is most common; robotic-assisted surgery is covered at the same Medicare rates.
• Low anterior resection (LAR): for mid and upper rectal cancers; preserves the rectum and avoids permanent colostomy in most cases.
• Abdominoperineal resection (APR): for tumors in the lowest portion of the rectum or anal canal; requires a permanent colostomy.
• Transanal endoscopic microsurgery (TEM/TAMIS): minimally invasive local excision for very early-stage (T1) rectal cancers; performed through the anus without abdominal incisions.
• Liver resection: for colorectal cancer that has spread to the liver; covered under Part A (inpatient) or Part B (outpatient) depending on complexity and required hospital stay.
• Cytoreduction and HIPEC (hyperthermic intraperitoneal chemotherapy): for peritoneal metastases from colorectal cancer; major inpatient surgery covered under Part A.

Cost-sharing for surgery: For Part A inpatient surgery, you pay the Part A inpatient deductible ($1,736 per benefit period in 2026), then $0 for days 1–60. For Part B outpatient surgery, you pay the Part B deductible ($283) plus 20% coinsurance on the Medicare-approved rate for the procedure and anesthesia. For major cancer surgery with complex facility fees, this 20% can represent thousands of dollars without a Medigap plan. For the full Part A cost structure, see Medicare Part A coverage.

Ostomy Supplies Under Part B as Durable Medical Equipment

When colorectal cancer surgery results in a colostomy or ileostomy — whether permanent (after APR) or temporary (to protect a newly constructed bowel anastomosis while it heals) — Medicare Part B covers ongoing ostomy supplies as durable medical equipment (DME).

Covered supplies include colostomy and ileostomy pouching systems (one-piece and two-piece), skin barriers, drainable pouches, closed-end pouches, ostomy irrigation systems, and ostomy accessories such as adhesive remover, barrier rings, and paste. These supplies are ordered on a recurring basis, typically monthly.

Cost-sharing: Standard Part B DME cost-sharing applies — 20% coinsurance after the annual deductible. Ostomy supplies for an active ostomy user typically cost $100–$200 per month in total; your 20% share is $20–$40/month. A Medigap Plan G policy covers this coinsurance entirely. Medigap Plans Compared shows which supplement plans include DME coverage.

Supplies must be ordered through a Medicare-enrolled DME supplier. Your ostomy care nurse or hospital discharge planner can connect you with suppliers — confirm they accept Medicare assignment to avoid surprise bills.

Radiation Therapy Under Part B

Radiation therapy is a standard component of treatment for rectal cancer (not typically used for colon cancer). Medicare Part B covers all modalities:

Neoadjuvant chemoradiation for Stage II–III rectal cancer: Before surgery, patients typically receive 5 to 6 weeks of daily external beam radiation combined with concurrent low-dose fluorouracil infusion. This shrinks the tumor, may convert an APR (permanent colostomy) to a sphincter-sparing LAR, and improves local control. The radiation component bills under Part B at 20% coinsurance per session; the concurrent 5-FU infusion also bills under Part B.

Short-course radiation (5×5): Five fractions of higher-dose radiation over one week, used particularly in patients who need to start systemic chemotherapy quickly.

SBRT/SABR for oligometastatic disease: Stereotactic body radiation therapy for isolated liver or lung metastases from colorectal cancer is covered under Part B when used to ablate limited sites of disease — a potentially curative approach for a subset of Stage IV patients.

A full course of radiation (typically 25–28 sessions for neoadjuvant rectal cancer) generates cumulative coinsurance. For a patient without Medigap, this can reach $1,000–$2,000 in coinsurance for radiation alone — before surgery, chemotherapy, or targeted therapy costs.

IV Chemotherapy and Targeted Biologics Under Part B

Medicare Part B covers all physician-administered chemotherapy — drugs infused or injected by a nurse or physician in a clinical setting. This is where the most significant financial exposure lies for colorectal cancer patients, because the targeted biologics used in metastatic CRC are among the most expensive drugs in oncology.

Standard Chemotherapy Regimens

The core chemotherapy drugs for colorectal cancer are fluorouracil (5-FU), leucovorin (LV), oxaliplatin, and irinotecan — all IV drugs covered under Part B:

FOLFOX is the standard adjuvant regimen after surgery for Stage III colon cancer. FOLFOX or FOLFIRI is used first-line for metastatic disease, often combined with a targeted biologic.

Anti-VEGF Targeted Biologics

Vascular endothelial growth factor (VEGF) inhibitors are added to chemotherapy in first- and second-line treatment regardless of tumor molecular subtype:

Bevacizumab (Avastin) is the most widely used targeted biologic in metastatic colorectal cancer. It is a VEGF antibody given every 2–3 weeks as a 30–90 minute IV infusion. The Medicare-approved rate for bevacizumab typically ranges from $3,000–$5,000 per infusion cycle; your 20% Part B coinsurance is therefore $600–$1,000 per infusion cycle. For patients receiving bevacizumab every two weeks through a year of treatment (approximately 24–26 cycles), annual coinsurance exposure without Medigap can reach $15,000–$25,000 — and that’s before surgery or other chemotherapy costs.

Ramucirumab (Cyramza) and ziv-aflibercept (Zaltrap) are alternatives used in second-line settings, also covered under Part B at the same 20% coinsurance structure.

Anti-EGFR Targeted Biologics (RAS Wild-Type Tumors Only)

Epidermal growth factor receptor (EGFR) inhibitors are effective only in colorectal cancers that have not mutated the RAS genes (KRAS and NRAS). Approximately 40–50% of colorectal cancers are RAS wild-type and eligible:

Cetuximab (Erbitux): given weekly or biweekly IV. One of the most expensive cancer biologics, with monthly costs of $10,000–$14,000. Your 20% Part B coinsurance without Medigap could reach $2,000–$2,800 per month for cetuximab alone.

Panitumumab (Vectibix): given every 2 weeks IV. Similar cost range and similar coinsurance exposure.

Immunotherapy for MSI-H/dMMR Colorectal Cancer

Approximately 15% of metastatic colorectal cancers are classified as MSI-H (microsatellite instability–high) or dMMR (deficient mismatch repair). This molecular subtype — which has particular treatment implications and hereditary significance (see Lynch syndrome section below) — responds dramatically to immunotherapy:

Pembrolizumab (Keytruda) is FDA-approved and Medicare-covered as first-line treatment for MSI-H/dMMR metastatic colorectal cancer. A pembrolizumab infusion takes 30 minutes and is given every 3–6 weeks; responses can be durable. For RAS-mutated tumors with MSI-H status, pembrolizumab is often preferred over chemotherapy as initial therapy given dramatically superior response rates.

Nivolumab (Opdivo) is approved for MSI-H/dMMR colorectal cancer after prior treatment and is covered under Part B.

Both drugs cost approximately $10,000–$14,000 per cycle. Without a Medigap supplement, the 20% Part B coinsurance represents $2,000–$2,800 per infusion cycle — and these drugs are given for as long as they’re working and tolerated.

HER2-Targeted and BRAF-Targeted Biologics

HER2-amplified colorectal cancer (approximately 3–4% of cases) can be treated with trastuzumab (Herceptin) combined with pertuzumab (Perjeta), both covered under Part B as IV infusions.

BRAF V600E–mutated colorectal cancer (approximately 10–15% of cases) is treated with the combination of encorafenib (oral, Part D) plus cetuximab (IV, Part B) — a hybrid oral/IV regimen that becomes relevant for Part B and Part D cost-sharing simultaneously.

The bottom line on Part B cost exposure: Original Medicare has no annual out-of-pocket cap for Part B services. A patient with metastatic CRC receiving FOLFOX plus bevacizumab could face $15,000–$30,000 per year in Part B coinsurance alone — before any other healthcare costs. Medigap Plan G covers 100% of Part B coinsurance, reducing these costs to $0 after the annual $283 deductible. If you’re approaching Medicare eligibility, the decision to enroll in Medigap — made at age 65 during the guaranteed-issue open enrollment period — may be the single most important financial protection you can put in place.

For the full cost comparison between Medigap supplements and Medicare Advantage for cancer treatment, see Medicare Supplement vs. Advantage Costs.

Oral Cancer Drugs Under Medicare Part D

Several important colorectal cancer drugs are taken at home in pill form, placing them under Medicare Part D rather than Part B. The $2,100 annual out-of-pocket cap under Part D (effective 2026 under the Inflation Reduction Act) is critical for these expensive oral cancer agents:

Once you reach the $2,100 annual Part D out-of-pocket limit, your plan pays 100% of covered drug costs for the rest of the year — effectively making these drugs free from that point forward. For patients on Lonsurf, Stivarga, Lumakras, or Krazati at their full price, the cap is typically reached within the first month or two of therapy.

Capecitabine (generic available) is the most commonly used oral colorectal cancer drug. The generic version is significantly less expensive than brand-name Xeloda and is widely available at Tier 2 copays. See Medicare Part D explained for how formulary tiers and the annual out-of-pocket cap work together.

Lynch Syndrome and Genetic Testing

Lynch syndrome — caused by inherited mutations in mismatch repair (MMR) genes — is the most common hereditary colorectal cancer syndrome and accounts for 3–5% of all colorectal cancer cases. It also increases risk of uterine, ovarian, gastric, and urinary tract cancers.

Tumor testing: Medicare covers MMR immunohistochemistry (IHC) or MSI PCR testing on tumor tissue for all newly diagnosed colorectal cancer patients as a covered Part B laboratory service. This testing serves two purposes: it identifies MSI-H/dMMR tumors eligible for immunotherapy, and it identifies patients who should be offered Lynch syndrome genetic testing.

Germline genetic testing: If tumor testing shows dMMR (mismatch repair deficiency), germline genetic testing for Lynch syndrome is covered under Part B when ordered by a physician. A positive germline result has implications not just for the patient but for first-degree relatives, who may benefit from preventive colonoscopy starting at age 20–25.

Surveillance colonoscopy for Lynch syndrome: Lynch syndrome carriers have a 40–80% lifetime risk of colorectal cancer. Medicare covers surveillance colonoscopy every 1–2 years for confirmed Lynch syndrome patients — the high-risk frequency, not the standard 10-year average-risk interval.

Medicare Advantage vs. Original Medicare for Colorectal Cancer

The choice between Original Medicare with a Medigap supplement and Medicare Advantage is especially consequential for colorectal cancer patients. Key considerations:

Prior authorization: Most Medicare Advantage plans require prior authorization for chemotherapy regimens, targeted biologics, and advanced imaging (PET scans, pelvic MRI). Starting treatment can be delayed while authorizations are processed. Original Medicare generally does not require prior authorization for covered services.

Access to NCI-designated cancer centers: The National Cancer Institute designates cancer centers with demonstrated expertise in complex cancer care. For Stage III–IV colorectal cancer, MSI-H/dMMR tumors, BRAF-mutated tumors, and candidates for liver resection, an NCI-designated cancer center often provides superior multidisciplinary care. These centers may be out-of-network for many Medicare Advantage plans. With Original Medicare and Medigap, any Medicare-participating provider — including all NCI cancer centers — is in-network.

The Medigap enrollment window: Medigap plans offer guaranteed-issue enrollment only during your six-month open enrollment period that starts when you turn 65 and enroll in Part B. After that window closes, insurance companies in most states can use medical underwriting — meaning a colorectal cancer diagnosis can make you uninsurable for Medigap or result in premium surcharges. If you’re currently on Medicare Advantage and diagnosed with colorectal cancer, transitioning to Medigap may not be possible. This is why enrolling in a comprehensive Medigap plan at 65 is the strongest long-term financial protection strategy — before any diagnosis occurs.

For a complete analysis of coverage options and their implications for serious illness, see Medicare Advantage vs. Original Medicare.

Low-Income Cost Assistance

If you have limited income, two programs help reduce colorectal cancer treatment costs:

Medicare Savings Programs (MSPs): The Qualified Medicare Beneficiary (QMB) program pays your Part B deductible and 20% coinsurance — which can eliminate all your out-of-pocket costs for surgery, chemotherapy, and targeted biologics. This is the most valuable cost-assistance program for colorectal cancer patients on limited income. See Medicare Savings Programs for eligibility details.

Extra Help (Low Income Subsidy): For Part D drug costs, Extra Help eliminates the Part D deductible and caps copayments at $4.90–$11.20 for most drugs. Combined with the $2,100 annual cap, this can make oral cancer drugs essentially free for qualifying beneficiaries.

Colorectal Cancer and Diabetes: A Common Comorbidity

Type 2 diabetes increases colorectal cancer risk by approximately 20–30%, likely through the effects of insulin resistance, hyperinsulinemia, and chronic inflammation on colon cell growth. Medicare beneficiaries with diabetes — a very common comorbidity in this age group — should be particularly conscientious about colorectal cancer screening. For how Medicare covers the broader spectrum of diabetes management and its complications, see Medicare coverage for diabetes.

Cost Summary: What You’ll Pay Under Different Coverage Options

The table illustrates why Medigap Plan G is often called the cancer patient’s financial firewall: while original Medicare without supplement leaves the total Part B coinsurance unlimited, Medigap Plan G converts all of those costs to $0 beyond the $283 annual deductible.

Your Seven-Step Colorectal Cancer Coverage Plan

1. Get your free screening colonoscopy: If you have not had a colonoscopy in the past 10 years (or 2 years if high-risk), schedule one under your Part B preventive benefit — at $0. This is the most cost-effective cancer prevention step available.

2. Know your biomarker status: For any Stage III–IV diagnosis, ensure your tumor is tested for RAS, BRAF, MSI/MMR, HER2, and KRAS G12C. These results determine which targeted therapies you’re eligible for and whether immunotherapy (pembrolizumab) is a first-line option.

3. Evaluate Medigap vs. Medicare Advantage before starting treatment: If you’re at the decision point, Part B coinsurance exposure for metastatic CRC treatment without Medigap can reach $30,000–$50,000 per year. If you’re already in Medicare Advantage, explore whether your plan’s network includes NCI centers and what prior authorization requirements apply.

4. Enroll in Part D if you’re not already: Oral cancer drugs (capecitabine, regorafenib, Lonsurf, Lumakras) require Part D. The $2,100 annual cap makes even the most expensive oral cancer drugs manageable.

5. Apply for Medicare Savings Programs if your income qualifies: QMB eliminates Part B coinsurance entirely. See Medicare Savings Programs for how to apply.

6. Ask your oncologist about clinical trials: Medicare covers routine costs associated with qualifying clinical trials. Clinical trial participation can provide access to investigational agents at no additional cost. See Medicare Coverage for Cancer Treatment for how clinical trial coverage works.

7. Ask about Lynch syndrome testing: If your tumor shows dMMR, germline genetic testing for Lynch syndrome is covered under Part B. A positive result has implications for your family members’ cancer risk.

Frequently Asked Questions

Does Medicare cover a colonoscopy at no cost? Yes. A preventive screening colonoscopy is covered by Medicare Part B with no deductible and no coinsurance. Since 2023, the procedure remains covered as preventive (no coinsurance) even if polyps are found and removed during the same session. Separately billed anesthesia and pathology services may still carry standard Part B 20% coinsurance.

What does Medicare pay for Cologuard? Medicare covers Cologuard (stool DNA test) at no cost every 3 years for average-risk adults ages 45–75 under the Part B preventive benefit — no deductible, no coinsurance.

If I need surgery, will I owe the full Part A deductible? If your colorectal cancer surgery requires a formal inpatient hospital admission, the Part A inpatient deductible applies ($1,736 per benefit period in 2026). Medigap Plan G covers this deductible fully. If surgery is classified as outpatient, Part B cost-sharing applies instead.

What will I pay for chemotherapy infusions? Under Original Medicare without a supplement, you pay 20% of the Medicare-approved rate for each infusion. For expensive targeted biologics like bevacizumab, cetuximab, or pembrolizumab, this can be $800–$2,800 per infusion cycle. With Medigap Plan G, your coinsurance is $0 after the annual Part B deductible. There is no annual cap on Part B out-of-pocket costs without a supplement.

Does Medicare cover oral cancer pills like Xeloda or Lonsurf? Yes. Oral cancer drugs are covered under Medicare Part D. The $2,100 annual out-of-pocket cap (2026) means your total annual cost for all Part D drugs combined — including expensive medications like Lonsurf or Stivarga — is capped at $2,100. Once you reach the cap, covered drugs are free for the rest of the year.

Does Medicare cover colostomy bags and ostomy supplies? Yes. Medicare Part B covers ostomy pouching systems, skin barriers, and supplies as durable medical equipment (DME). Standard 20% Part B coinsurance applies, which is covered by Medigap plans. Supplies must be obtained from a Medicare-enrolled DME supplier.