As CT scan usage in the United States has increased by 35% since 2007, a shocking new study reveals these common diagnostic tools may be responsible for 5% of all annual cancer cases.
At a Glance
- A recent UC San Francisco study suggests CT scans may account for 5% of all U.S. cancer diagnoses annually
- Radiation exposure from CT scans varies dramatically, with some facilities emitting doses 50 times stronger than others
- Children and adolescents face the greatest risk from radiation exposure, though adults undergo more scans
- Alternative imaging methods like MRI and ultrasound don’t expose patients to radiation
- Patients should discuss with doctors whether CT scans are necessary and request low-dose options when possible
Understanding CT Scans and Their Uses
Computed tomography (CT) is a noninvasive imaging procedure that uses x-ray equipment to create detailed cross-sectional pictures of the body. Modern CT machines employ helical (spiral) imaging technology, which provides faster scans and produces higher quality three-dimensional images. These detailed images allow physicians to see inside the body with remarkable clarity, helping them diagnose conditions that might otherwise require invasive procedures.
CT scans play a crucial role in cancer diagnosis, treatment planning, and monitoring. They’re used for screening certain high-risk populations, staging existing cancers, guiding biopsies of suspicious areas, and planning radiation treatments. For many patients facing potential health crises, CT scans provide vital information that guides life-saving medical decisions.
The Cancer Risk Connection
The concern with CT scans stems from their use of ionizing radiation to create images. Unlike ultrasound or MRI, which use sound waves or magnetic fields, CT scans expose patients to radiation that can damage DNA and potentially lead to cancer. A groundbreaking study from UC San Francisco researchers suggests that CT scans could account for approximately 5% of all cancer cases diagnosed in the United States annually – a figure significantly higher than previously estimated.
Perhaps most alarming is the wide variation in radiation exposure between facilities. Some patients receive radiation doses up to 50 times stronger than others for the same type of scan. This inconsistency exists because there are currently no federal standards for CT scan dosages, though efforts are underway to develop quality measures. The UCSF study found that abdominal and pelvic CT scans contributed most significantly to projected cancer cases due to their higher radiation use.
Increased use of CT scans could lead to many more cancer cases, a study finds. “Most patients will not develop cancer from a CT scan,” Dr. @UCRadSafety tells @KQED. “But if you’re not getting any benefit, then even a small risk is unacceptable.” https://t.co/tsaHiljP3H
— UCSF Health (@UCSFHospitals) April 14, 2025
Who Faces the Greatest Risk?
Children and adolescents face the highest risk from radiation exposure since their cells divide more rapidly and they have more years ahead for radiation-induced cancers to develop. Parents should be particularly vigilant about questioning the necessity of CT scans for their children and asking about alternative imaging options. However, adults are not immune to these risks and are more likely to undergo multiple scans over their lifetime.
Some CT scans appear to be overused with limited clinical benefit. For example, scans for upper respiratory infections or headaches without concerning symptoms may expose patients to radiation without significantly improving diagnosis or treatment. Since 2007, CT scan usage has increased by 35%, with a significant portion attributed to “low-value, potentially unnecessary imaging.” This rise in usage amplifies population-level cancer risk.
Balancing Benefits and Risks
Despite these concerns, the medical community emphasizes that CT scans provide crucial benefits that often outweigh potential risks. They enable early detection of serious conditions, guide precise treatment planning, help patients avoid invasive diagnostic procedures, and provide critical information in emergency situations. In many cases, the immediate health benefit of having a needed CT scan far exceeds the small long-term cancer risk.
For instance, the National Lung Screening Trial demonstrated that annual low-dose CT screening reduced lung cancer mortality by 20% in high-risk individuals. CT imaging has contributed significantly to public health benefits, including lower cancer mortality rates and fewer invasive surgeries. Patients should not refuse necessary scans but should engage in informed discussions about their necessity and alternatives.
Safer Alternatives and Risk Reduction Strategies
When appropriate, patients can request imaging alternatives that don’t use ionizing radiation. MRI uses magnetic fields and radio waves to create detailed images without radiation exposure. Ultrasound uses sound waves and is particularly useful for examining soft tissues. These alternatives may not be suitable for all diagnostic needs but can significantly reduce radiation exposure when applicable.
The medical community has launched initiatives to reduce unnecessary radiation exposure, including campaigns like Image Gently for pediatric patients and Image Wisely for adults. Organizations like the FDA and NIH have developed guidelines to promote appropriate use of imaging. Strategies include using clinical decision support tools, reducing multiphase scans, standardizing radiation protocols, and tracking cumulative exposure. Patients should maintain records of their imaging history and discuss it with healthcare providers.
