Do CT Scans Cause Cancer? 2026 Evidence on Radiation Risks, Key Studies, and Patient Advice

CT scans save lives every day by detecting life-threatening conditions like tumors, internal bleeding, and trauma injuries. But a heated debate erupted on X (formerly Twitter) in May 2026 when Canadian cancer researcher Dr. William Makis (@MakisMedicine) called out an oncologist for claiming CT scans “do not cause cancer.” Makis urged patients to “run away” from any doctor dismissing radiation risks and backed it up with peer-reviewed studies. So, what does the science actually say in 2026? Is the risk real, or is it overhyped? Here’s a clear, evidence-based breakdown.

What Is a CT Scan and Why Does It Use Radiation?

A computed tomography (CT) scan — also called a CAT scan — combines X-rays from multiple angles to create detailed 3D images of your organs, bones, and tissues. Unlike a regular X-ray, it delivers significantly more ionizing radiation.
Ionizing radiation can damage DNA. Under the linear no-threshold (LNT) model used by regulators worldwide, any dose carries some cancer risk — though the absolute risk from a single scan remains very small.
Typical effective doses (in millisieverts, mSv):

• Chest X-ray: 0.1 mSv
• Mammogram: 0.4 mSv
• Abdominal/pelvic CT: 8–10 mSv (roughly 3 years of natural background radiation)
• Head CT: 2 mSv
• Whole-body PET-CT: 25+ mSv

Image credit: touchstoneimaging.com

The Science: Major Studies Linking CT Radiation to Cancer Risk

1. Pearce et al. (2012) – The Lancet
This landmark UK retrospective cohort study of 178,604 children and young adults found clear dose-dependent increases in leukemia and brain tumors. Just 2–3 head CTs roughly tripled brain tumor risk; 5–10 head CTs tripled leukemia risk. The excess risk appeared within the first decade after exposure. (PubMed)
2. Cao et al. (2022) – BMC Cancer
A systematic review and dose-response meta-analysis of millions of adults confirmed that higher cumulative CT radiation doses correlate with elevated overall cancer odds ratios. Risks rose with more scans and higher-dose body regions (abdomen/pelvis carried the highest risk). (BMC Cancer)
3. Yaw et al. (2026) – Communications Medicine (Nature)
Published January 2026, this study analyzed trauma patients and found a statistically significant dose-dependent link between CT radiation during hospitalization and later new-onset cancer incidence and cancer-related mortality. Even after adjusting for confounders, higher dose-length product (DLP) increased hazard ratios. (Nature 2026)
4. Smith-Bindman et al. (2025) – JAMA Internal Medicine
The most impactful recent modeling study used real-world data from 93 million CT scans performed in the U.S. in 2023. Researchers projected ~103,000 future radiation-induced cancers — potentially accounting for up to 5% of all new annual cancer diagnoses. Abdomen/pelvis scans drove the largest share (37%). Children and younger patients face higher relative risks, but sheer volume in adults means most projected cancers occur later in life. These studies align with the FDA, NCI, and BEIR VII reports: the risk is small per scan but cumulative and non-zero. (JAMA)

The Counter-Argument: Benefits Usually Outweigh Risks

Most medical bodies (Mayo Clinic, MD Anderson, Harvard Health) emphasize that one appropriately ordered CT scan carries very low absolute risk — often estimated at 1 in 1,000 to 1 in 10,000 added lifetime cancer risk depending on age, sex, and body part. Doctors follow the ALARA principle (“As Low As Reasonably Achievable”) and only order CTs when the diagnostic benefit is clear — for example, staging lung cancer, detecting appendicitis, or evaluating trauma where MRI isn’t practical or fast enough.
No large-scale “cancer pandemic” has been directly tied to diagnostic CTs alone, partly because modern scanners use lower doses and because cancer has many causes.

The Viral X Debate: Dr. Makis vs. Swiss Oncologist

In the May 20, 2026 post that went viral, Dr. Makis directly rebutted Dr. Yannick Buccella’s claim that CTs pose negligible risk (comparing one scan to a pilot’s yearly cosmic radiation). Makis called it “misinformation” and cited the exact studies above, warning patients to seek second opinions if their oncologist dismisses radiation entirely.
Makis, a nuclear medicine physician and cancer researcher with over 100 publications, has long advocated for radiation awareness alongside repurposed drug research. While tone can be alarmist, his core point — that risks are real and should be discussed transparently — is supported by the data.

When Should You Worry? Practical Patient Tips

• Cumulative exposure matters most. Multiple scans over years (especially abdomen/pelvis) raise risk more than a single scan.
• Children and young adults are more radiosensitive — ask about dose-reduction protocols or non-ionizing alternatives first.
• Ask questions: “Is this CT necessary? Can we use MRI or ultrasound instead? What dose will I receive?”
• Track your history — bring a list of past scans to appointments.

Safer alternatives when clinically appropriate:

• MRI (no ionizing radiation — excellent for soft tissue/brain)
• Ultrasound
• Low-dose CT protocols (now standard for lung cancer screening)

Bottom Line: Informed Consent Is Key

CT scans are a powerful tool and will remain essential in modern medicine. However, 2025–2026 research shows they are not risk-free. The projected 103,000 future cancers from just one year’s scans in the U.S. alone should prompt every patient and doctor to weigh benefits carefully and minimize unnecessary or repeated imaging.
Always discuss risks and alternatives with your physician. If your oncologist or radiologist brushes off radiation concerns without nuance, a second opinion is reasonable — exactly as Dr. Makis advised.
Have you had multiple CT scans? Share your experience in the comments (and always consult your doctor before changing any medical plan).

FAQ: CT Scan Cancer Risk

Q: How many CT scans are “too many”?
A: There is no strict number — risk is cumulative. Most experts become more cautious after 3–5 scans in a short period, especially in younger patients.
Q: Do modern CT scanners reduce risk?
A: Yes. Newer machines use 30–50% lower doses than those from 10–15 years ago, plus AI dose-optimization.
Q: Is the risk higher for cancer patients already getting scans?
A: Yes, but in active cancer care the benefit of accurate staging almost always outweighs the added radiation risk.
Q: Should I refuse a CT if recommended?
A: No — never refuse a medically necessary scan without discussion. The goal is informed shared decision-making.
Sources include peer-reviewed studies from The Lancet, BMC Cancer, Communications Medicine, and JAMA Internal Medicine (2025–2026). This article is for educational purposes only and not medical advice.