What are common side effects of radiation therapy

June 3, 2026Navis AI

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For informational purposes only

This answer was generated by AI grounded in NCCN guidelines and published medical literature. It is not medical advice. Always consult your oncologist or care team before making treatment decisions.

Sources & medical oversight

Developed under the medical oversight of OpenCancer’s physician-scientist team (Chris Apfel, MD/PhD/MBA, CMO · Kaumudi Bhawe, PhD, CSO).
Last updated June 3, 2026. Informational only — not a substitute for your oncology team.

Common Side Effects of Radiation Therapy

Radiation therapy works by targeting cancer cells with high-energy beams, but it can also affect healthy tissue nearby. Here are the most common side effects:

During & Shortly After Treatment (Acute Side Effects)

Skin reactions — The most visible side effect. Your skin in the treatment area may become red, irritated, or darkened (like a sunburn). This typically peaks around the 2nd-3rd week of treatment and gradually improves after therapy ends.

Fatigue — Many patients experience tiredness during treatment, which can persist for weeks or months afterward. This is one of the most common complaints.

Hair loss — Only in the specific area being treated. Hair may thin or fall out, though it often regrows after treatment completes.

Nausea and loss of appetite — Especially with abdominal or pelvic radiation. Anti-nausea medications can help manage this.

Mouth/throat problems — If treating the head/neck area, you may experience dry mouth, difficulty swallowing, or mouth sores.

Long-Term Side Effects (Months to Years Later)

Fibrosis — Scarring of tissue in the treatment area, which can cause stiffness or reduced function.

Secondary cancers — Rarely, radiation can increase the risk of developing a different cancer years later in or near the treatment field.

Organ damage — Depending on location, radiation can affect heart, lungs, or other organs over time.

Important Context

Side effects vary greatly depending on:

Type of radiation (external beam vs. brachytherapy)
Dose and duration of treatment
Location being treated
Your individual factors (age, overall health, other treatments)

According to the American Cancer Society and NCCN Guidelines, your radiation oncology team will work with you to manage side effects through supportive care, medications, and lifestyle strategies. Many side effects are temporary and manageable.

Questions to ask your radiation oncologist:

What side effects are most likely for MY specific treatment plan?
What can I do to minimize side effects?
When should I contact you about a side effect?
Are there medications or supportive care options available?
How long will side effects typically last?

This information is for educational purposes only. Always consult your healthcare team for personalized medical advice and decisions.

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