Espa?ol
PDFs by language
Our 24/7 cancer helpline provides information and answers for people dealing with cancer. We can connect you with trained cancer information specialists who will answer questions about a cancer diagnosis and provide guidance and a compassionate ear.
Chat live online
Select the Live Chat button at the bottom of the page
Call us at 1-800-227-2345
Available any time of day or night
Our highly trained specialists are available 24/7 via phone and on weekdays can assist through online chat. We connect patients, caregivers, and family members with essential services and resources at every step of their cancer journey. Ask us how you can get involved and support the fight against cancer. Some of the topics we can assist with include:
For medical questions, we encourage you to review our information with your doctor.
Tumor treating fields (also known as TTFields) are a type of cancer therapy that use low-energy electrical fields to disrupt cancer cells’ ability to grow and divide. TTFields may also be called alternating electric fields.
TTFields are delivered through a special portable device with electrodes that are placed on your skin near the tumor. These electrodes are connected to a portable battery that you can carry in a backpack. The device sends mild electrical currents that target cancer cells while sparing most nearby healthy cells. The TTFields device usually needs to be worn for at least 18 hours each day, but people can continue most of their daily activities while wearing it.
TTFields may be used alone or along with other treatments, such as chemo. TTFields tend to have few side effects (see below), so they may be used if other treatments have already been tried.
Two tumor treating fields devices are FDA-approved to treat cancer:
Research studies are also looking at using TTFields for other types of cancers, such as pancreatic, non-small cell lung, ovarian, and breast cancer.
TTFields do use radiation, but it’s a different type of radiation than traditional radiation therapy. The electrical fields created in TTFields are a type of non-ionizing radiation. Other types of non-ionizing radiation include radio waves, microwaves, and visible and infrared light.
Non-ionizing radiation doesn’t have as much energy as ionizing radiation does. Traditional radiation therapy uses high-energy ionizing radiation to kill cancer cells. Ionizing radiation can damage healthy cells nearby, which can cause side effects.
Since TTFields use low energy, non-ionizing radiation, side effects tend to be mild. The most common side effect is skin irritation in the area where the electrodes are worn.
Other side effects are also possible, depending on where the electrodes are placed on the body. For example, TTFields devices worn on the scalp can cause:
Some people might not be good candidates for treatment with TTFields, because of other health issues they have. Talk to your doctor to learn more about whether this type of treatment might be right for you.
Learn more about how TTFields are used to treat glioblastoma and mesothelioma.
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.
Batchelor T, Shih HA. Management of glioblastoma in older adults. UpToDate. UpToDate; 2024. Updated August 2023. Accessed July 23rd, 2024. https://www.uptodate.com/contents/management-of-glioblastoma-in-older-adults
Batchelor T, Shih HA, Carter BS. Management of recurrent high-grade gliomas. UpToDate. UpToDate; 2024. Updated July 2024. Accessed July 22nd, 2024. https://www.uptodate.com/contents/management-of-recurrent-high-grade-gliomas
Moser JC, Salvador E, Deniz K, et al. The mechanisms of action of tumor treating fields. Cancer Res. 2022; 82(20):3650–3658. doi.org/10.1158/0008-5472.CAN-22-0887
NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines). Central Nervous System Cancers. Version 1.2024. Updated May 2024. National Comprehensive Cancer Network. Accessed July 23rd, 2024. https://www.nccn.org/professionals/physician_gls/pdf/cns.pdf
NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines). Mesothelioma: Pleural. Version 1.2024. Updated November 2023. National Comprehensive Cancer Network. Accessed July 23rd, 2024. https://www.nccn.org/professionals/physician_gls/pdf/meso_pleural.pdf
Tsao AS. Systemic treatment for unresectable malignant pleural mesothelioma. UpToDate. UpToDate; 2024. Updated April 2024. Accessed July 22nd, 2024. https://www.uptodate.com/contents/systemic-treatment-for-unresectable-malignant-pleural-mesothelioma
Last Revised: July 25, 2024
American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.
Sign up to stay up-to-date with news, valuable information, and ways to get involved with the American Cancer Society.
If this was helpful, donate to help fund patient support services, research, and cancer content updates.